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# crypto (crypto v5.8.3)

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Crypto Functions

This module provides a set of cryptographic functions.

- Hash functions -

  - SHA1, SHA2 - Secure Hash Standard (FIPS PUB180-4)

  - SHA3 - SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions (FIPS PUB 202)

  - BLAKE2 - BLAKE2 — fast secure hashing

  - SM3 - The SM3 Hash Function (GM/T 0004-2012)

  - MD5 - The MD5 Message Digest Algorithm (RFC 1321)

  - MD4 - The MD4 Message Digest Algorithm (RFC 1320)

- MACs - Message Authentication Codes -

  - Hmac functions - Keyed-Hashing for Message Authentication (RFC 2104)

  - Cmac functions - The AES-CMAC Algorithm (RFC 4493)

  - POLY1305 - ChaCha20 and Poly1305 for IETF Protocols (RFC 7539)

- Symmetric Ciphers -

  - DES, 3DES and AES - Block Cipher Techniques (NIST)

  - Blowfish - Fast Software Encryption, Cambridge Security Workshop Proceedings (December 1993), Springer-Verlag, 1994, pp. 191-204.

  - Chacha20 - ChaCha20 and Poly1305 for IETF Protocols (RFC 7539)

  - Chacha20_poly1305 - ChaCha20 and Poly1305 for IETF Protocols (RFC 7539)

  - SM4 - The SM4 Block Cipher Algorithm

- Modes -

  - ECB, CBC, CFB, OFB and CTR - Recommendation for Block Cipher Modes of Operation: Methods and Techniques (NIST SP 800-38A)

  - GCM - Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC (NIST SP 800-38D)

  - CCM - Recommendation for Block Cipher Modes of Operation: The CCM Mode for Authentication and Confidentiality (NIST SP 800-38C)

- Asymmetric Ciphers - Public Key Techniques -

  - RSA - PKCS #1: RSA Cryptography Specifications (RFC 3447)

  - DSS - Digital Signature Standard (DSS) (FIPS 186-4)

  - ECDSA - Elliptic Curve Digital Signature Algorithm (ECDSA)

  - SRP - The SRP Authentication and Key Exchange System (RFC 2945)

#### Note

The actual supported algorithms and features depends on their availability in the actual libcrypto used. See the crypto (App) about dependencies.

Enabling FIPS mode will also disable algorithms and features.

The CRYPTO User's Guide has more information on FIPS, Engines and Algorithm Details like key lengths.

## Exceptions

### Atoms - the older style

The exception `error:badarg` signifies that one or more arguments are of wrong data type, or are otherwise badly formed.

The exception `error:notsup` signifies that the algorithm is known but is not supported by current underlying libcrypto or explicitly disabled when building that.

For a list of supported algorithms, see supports(ciphers).

### 3-tuples - the new style

The exception is:

    error:{Tag, C_FileInfo, Description}

    Tag = badarg | notsup | error
    C_FileInfo = term()    % Usually only useful for the OTP maintainer
    Description = string() % Clear text, sometimes only useful for the OTP maintainer

The exception tags are:

- `badarg` - Signifies that one or more arguments are of wrong data type or are otherwise badly formed.

- `notsup` - Signifies that the algorithm is known but is not supported by current underlying libcrypto or explicitly disabled when building that one.

- `error` - An error condition that should not occur, for example a memory allocation failed or the underlying cryptolib returned an error code, for example `"Can't initialize context, step 1"`. Those text usually needs searching the C-code to be understood.

Usually there are more information in the call stack about which argument caused the exception and what the values where.

To catch the exception, use for example:

    try crypto:crypto_init(Ciph, Key, IV, true)
        catch
            error:{Tag, _C_FileInfo, Description} ->
                do_something(......)
             .....
    end

## Summary

### Types: Ciphers

cipher()
cipher_aead()

Ciphers known by the CRYPTO application.

cipher_iv()
cipher_no_iv()
crypto_opt()

Selects encryption (`{encrypt,true}`) or decryption (`{encrypt,false}`).

crypto_opts()

Equivalent to `crypto_opt()`.

cryptolib_padding()

The `cryptolib_padding` are paddings that may be present in the underlying cryptolib linked to the Erlang/OTP crypto app.

otp_padding()

Erlang/OTP adds a either padding of zeroes or padding with random bytes.

padding()

This option handles padding in the last block. If not set, no padding is done and any bytes in the last unfilled block is silently discarded.

### Types: Diffie-Hellman Keys and parameters

dh_params()
dh_private()
dh_public()

Equivalent to `dh_private()`.

ecdh_params()
ecdh_private()

Equivalent to `ecdh_params()`.

ecdh_public()

Equivalent to `ecdh_params()`.

### Types: Digests and hash

blake2()
cmac_cipher_algorithm()
compatibility_only_hash()

The `compatibility_only_hash/0` algorithms are recommended only for compatibility with existing applications.

dss_digest_type()
ecdsa_digest_type()
hash_algorithm()
hash_xof_algorithm()
hmac_hash_algorithm()
rsa_digest_type()
sha1()

Equivalent to `blake2()`.

sha2()

Equivalent to `blake2()`.

sha3()

Equivalent to `blake2()`.

sha3_xof()

Equivalent to `blake2()`.

### Types: Elliptic Curves

ec_basis()

Curve definition details.

ec_characteristic_two_field()

Equivalent to `ec_basis()`.

ec_curve()

Parametric curve definition.

ec_explicit_curve()

Equivalent to `ec_curve()`.

ec_field()

Equivalent to `ec_curve()`.

ec_named_curve()

Equivalent to `edwards_curve_ed()`.

ec_prime_field()

Equivalent to `ec_basis()`.

edwards_curve_dh()

Equivalent to `edwards_curve_ed()`.

edwards_curve_ed()

Note that some curves are disabled if FIPS is enabled.

### Types: Internal data types

crypto_state()

Equivalent to `mac_state()`.

hash_state()

Equivalent to `mac_state()`.

mac_state()

Contexts with an internal state that should not be manipulated but passed between function calls.

### Types: Key Encapsulation Mechanism

kem()

Key encapsulation mechanisms.

### Types: Keys

key_integer()

Always `binary/0` when used as return value

### Types: Public Key Ciphers

pk_encrypt_decrypt_algs()

Algorithms for public key encrypt/decrypt. Only RSA is supported.

pk_encrypt_decrypt_opts()

Equivalent to `rsa_padding()`.

rsa_compat_opts()

Those option forms are kept only for compatibility and should not be used in new code.

rsa_opt()

Equivalent to `rsa_padding()`.

rsa_padding()

Options for public key encrypt/decrypt. Only RSA is supported.

### Types: Public Key Sign and Verify

pk_sign_verify_algs()

Algorithms for sign and verify.

pk_sign_verify_opts()

Equivalent to `rsa_sign_verify_padding()`.

rsa_sign_verify_opt()

Equivalent to `rsa_sign_verify_padding()`.

rsa_sign_verify_padding()

Options for sign and verify.

### Types: Public/Private Keys

dss_private()
dss_public()

Equivalent to `dss_private()`.

ecdsa_params()
ecdsa_private()

Equivalent to `ecdsa_params()`.

ecdsa_public()

Equivalent to `ecdsa_params()`.

eddsa_params()
eddsa_private()

Equivalent to `eddsa_params()`.

eddsa_public()

Equivalent to `eddsa_params()`.

rsa_params()
rsa_private()

Equivalent to `rsa_params()`.

rsa_public()

Equivalent to `rsa_params()`.

srp_comp_params()

Equivalent to `srp_host_comp_params()`.

srp_gen_params()

Equivalent to `srp_host_comp_params()`.

srp_host_comp_params()

Where Verifier is `v`, Generator is `g` and Prime is`N`, DerivedKey is `X`, and Scrambler is `u` (optional will be generated if not provided) from SRP design Version = '3' | '6' | '6a'

srp_host_gen_params()

Equivalent to `srp_host_comp_params()`.

srp_private()
srp_public()

Equivalent to `srp_private()`.

srp_user_comp_params()

Equivalent to `srp_host_comp_params()`.

srp_user_gen_params()

Equivalent to `srp_host_comp_params()`.

### Types: Types for Engines

engine_cmnd()

Pre and Post commands for engine_load/3 and /4.

engine_key_ref()

Equivalent to `engine_ref()`.

engine_method_type()
engine_ref()

The result of a call to `engine_load/3`.

key_id()

Identifies the key to be used. The format depends on the loaded engine. It is passed to the `ENGINE_load_(private|public)_key` functions in libcrypto.

password()

The password of the key stored in an engine.

### Types

crypto_integer()
mldsa()
mldsa_private()
mldsa_public()
rand_cache_seed()
slh_dsa()
slh_dsa_private()
slh_dsa_public()

### Cipher API

crypto_final(State)

Finalize a streaming encryptions or decryptions operation and delivers the final bytes of the final block.

crypto_get_data(State)

Return information about a `crypto_state/0`.

crypto_init(Cipher, Key, FlagOrOptions)

Initialize the state for a streaming encryption or decryption operation.

crypto_init(Cipher, Key, IV, FlagOrOptions)

Initialize the state for a streaming encryptions or decryptions operation.

crypto_one_time(Cipher, Key, Data, FlagOrOptions)

Do a complete encrypt or decrypt of the full text.

crypto_one_time(Cipher, Key, IV, Data, FlagOrOptions)

Do a complete encrypt or decrypt of the full text.

crypto_one_time_aead(State, IV, InText, AAD)

Do a complete encrypt or decrypt with an AEAD cipher of the full text.

crypto_one_time_aead(Cipher, Key, IV, InText, AAD, EncFlag)

Do a complete encrypt with an AEAD cipher of the full text with the default tag length.

crypto_one_time_aead(Cipher, Key, IV, InText, AAD, TagOrTagLength, EncFlag)

Do a complete encrypt or decrypt with an AEAD cipher of the full text.

crypto_one_time_aead_init(Cipher, Key, TagLength, EncFlag)

Initializes AEAD cipher.

crypto_update(State, Data)

Add data to a streaming encryption or decryption operation.

### Deprecated API

enable_fips_mode(Enable) deprecated

Enable or disable FIPs mode.

start() deprecated

Use `application:start(crypto)` instead.

stop() deprecated

Use `application:stop(crypto)` instead.

### Engine API

engine_add(Engine)

Add the engine to OpenSSL's internal list.

engine_by_id(EngineId)

Get a reference to an already loaded engine with `EngineId`. An error tuple is returned if the engine cannot be unloaded.

engine_ctrl_cmd_string(Engine, CmdName, CmdArg)

Send ctrl commands to an OpenSSL engine.

engine_ctrl_cmd_string(Engine, CmdName, CmdArg, Optional)

Send ctrl commands to an OpenSSL engine.

engine_get_all_methods()

Return a list of all possible engine methods.

engine_get_id(Engine)

Return the ID for the engine, or an empty binary if there is no id set.

engine_get_name(Engine)

Return the name (eg a description) for the engine, or an empty binary if there is no name set.

engine_list()

List the id's of all engines in OpenSSL's internal list.

engine_load(EngineId, PreCmds, PostCmds)

Load an OpenSSL engine.

engine_register(Engine, EngineMethods)

Register engine to handle some type of methods, for example engine_method_digests.

engine_remove(Engine)

Remove the engine from OpenSSL's internal list.

engine_unload(Engine)

Unload an OpenSSL engine.

engine_unregister(Engine, EngineMethods)

Unregister engine so it does not handle some type of methods.

ensure_engine_loaded(EngineId, LibPath)

Load a dynamic engine if not already done.

pbkdf2_hmac(Digest, Pass, Salt, Iter, KeyLen)

PKCS #5 PBKDF2 (Password-Based Key Derivation Function 2) in combination with HMAC.

privkey_to_pubkey(Type, EnginePrivateKeyRef)

Fetch public key from a private key stored in an Engine.

### Hash API

hash(Type, Data)

Compute a message digest.

hash_final(State)

Finalize a streaming hash calculation.

hash_init(Type)

Initialize the state for a streaming hash digest calculation.

hash_update(State, Data)

Add data to a streaming digest calculation.

hash_xof(Type, Data, Length)

Compute a message digest for an `xof_algorithm`.

### Key API

compute_key(Type, OthersPublicKey, MyPrivateKey, Params)

Compute the shared secret from the private key and the other party's public key.

decapsulate_key(Type, MyPrivKey, EncapSecret)

Regenerate shared secret from encapsulated secret and private key.

encapsulate_key(Type, OthersPublicKey)

Generate encapsulated shared secret from the other party's public key.

generate_key(Type, Params)

Equivalent to `generate_key/3`.

generate_key(Type, Params, PrivKeyIn)

Generate a public key.

### Legacy RSA Encryption API

private_decrypt(Algorithm, CipherText, PrivateKey, Options)

Decrypt using a private key.

private_encrypt(Algorithm, PlainText, PrivateKey, Options)

Encrypt using a private key.

public_decrypt(Algorithm, CipherText, PublicKey, Options)

Decrypt using a public key.

public_encrypt(Algorithm, PlainText, PublicKey, Options)

Encrypt using a public key.

### MAC API

mac(Type, Key, Data)

Compute a `poly1305` MAC (Message Authentication Code).

mac(Type, SubType, Key, Data)

Compute a MAC (Message Authentication Code).

mac_final(State)

Finalize a streaming MAC operation.

mac_finalN(State, MacLength)

Finalize a MAC operation with a custom length.

mac_init(Type, Key)

Initialize a state for streaming `poly1305` MAC calculation.

mac_init(Type, SubType, Key)

Initialize the state for streaming MAC calculation.

mac_update(State0, Data)

Add data to a streaming MAC calculation.

macN(Type, Key, Data, MacLength)

Compute a `poly1305` MAC (Message Authentication Code) with a limited length.

macN(Type, SubType, Key, Data, MacLength)

Compute a MAC (Message Authentication Code) with a limited length.

### Plug-In Generators

rand_seed()

Create a generator for `rand` and save it in the process dictionary.

rand_seed_alg(Alg)

Create a generator for `rand` with specified algorithm, and save it in the process dictionary.

rand_seed_alg(Alg, Seed)

Create and seed a generator for `rand` with specified algorithm, and save it in the process dictionary.

rand_seed_alg_s(Alg)

Create a generator for `rand` with specified algorithm.

rand_seed_alg_s(Alg, Seed)

Create and seed a generator for `rand` with specified algorithm.

rand_seed_s()

Create a generator for `rand`.

### Random API

rand_seed(Seed)

Mixes in the bytes of the given binary into the internal state of OpenSSL's random number generator.

rand_uniform/2 deprecated

Generate a random integer number.

strong_rand_bytes(N)

Generate bytes with randomly uniform values 0..255.

strong_rand_range/1

Generate a random integer in a specified range.

### Sign/Verify API

sign(Algorithm, DigestType, Msg, Key)

Equivalent to `sign/5`.

sign(Algorithm, DigestType, Msg, Key, Options)

Create a digital signature.

verify(Algorithm, DigestType, Msg, Signature, Key)

Equivalent to `verify/6`.

verify(Algorithm, DigestType, Msg, Signature, Key, Options)

Verify a digital signature.

### Utility Functions

bytes_to_integer(Bin)

Convert binary representation, of an integer, to an Erlang integer.

cipher_info(Type)

Get information about a cipher algorithm.

ec_curve(CurveName)

Return the defining parameters of a elliptic curve.

ec_curves()

Return all supported named elliptic curves.

exor(Bin1, Bin2)

Perform bit-wise XOR (exclusive or) on the data supplied.

hash_equals(BinA, BinB)

Compare two binaries in constant time, such as results of HMAC computations.

hash_info(Type)

Get information about a hash algorithm.

info()

Get information about crypto and the OpenSSL backend.

info_fips()

Get information about the operating status of FIPS.

info_lib()

Get the name and version of the libraries used by crypto.

mod_pow(N, P, M)

Compute the function `N^P mod M`.

supports(Type)

Get which crypto algorithms that are supported by the underlying libcrypto library.

## Types: Ciphers

# cipher()

(not exported)

    -type cipher() :: cipher_no_iv() | cipher_iv() | cipher_aead().

# cipher_aead()

(not exported)

    -type cipher_aead() ::
              aes_128_ccm | aes_192_ccm | aes_256_ccm | aes_ccm | aes_128_gcm | aes_192_gcm | aes_256_gcm |
              aes_gcm | sm4_gcm | sm4_ccm | chacha20_poly1305.

Ciphers known by the CRYPTO application.

Note that this list might be reduced if the underlying libcrypto does not support all of them.

# cipher_iv()

(not exported)

    -type cipher_iv() ::
              aes_128_cbc | aes_192_cbc | aes_256_cbc | aes_cbc | aes_128_ofb | aes_192_ofb | aes_256_ofb |
              aes_128_cfb128 | aes_192_cfb128 | aes_256_cfb128 | aes_cfb128 | aes_128_cfb8 | aes_192_cfb8 |
              aes_256_cfb8 | aes_cfb8 | aes_128_ctr | aes_192_ctr | aes_256_ctr | aes_ctr | sm4_cbc |
              sm4_ofb | sm4_cfb | sm4_ctr | blowfish_cbc | blowfish_cfb64 | blowfish_ofb64 | chacha20 |
              des_ede3_cbc | des_ede3_cfb | des_cbc | des_cfb | rc2_cbc.

# cipher_no_iv()

(not exported)

    -type cipher_no_iv() ::
              aes_128_ecb | aes_192_ecb | aes_256_ecb | aes_ecb | blowfish_ecb | des_ecb | sm4_ecb | rc4.

# crypto_opt()

(not exported)

    -type crypto_opt() :: {encrypt, boolean()} | {padding, padding()}.

Selects encryption (`{encrypt,true}`) or decryption (`{encrypt,false}`).

# crypto_opts()

(not exported)

    -type crypto_opts() :: boolean() | [crypto_opt()].

Equivalent to `crypto_opt()`.

# cryptolib_padding()

(not exported)

    -type cryptolib_padding() :: none | pkcs_padding.

The `cryptolib_padding` are paddings that may be present in the underlying cryptolib linked to the Erlang/OTP crypto app.

For OpenSSL, see the OpenSSL documentation. and find `EVP_CIPHER_CTX_set_padding()` in cryptolib for your linked version.

# otp_padding()

(not exported)

    -type otp_padding() :: zero | random.

Erlang/OTP adds a either padding of zeroes or padding with random bytes.

# padding()

(not exported)

    -type padding() :: cryptolib_padding() | otp_padding().

This option handles padding in the last block. If not set, no padding is done and any bytes in the last unfilled block is silently discarded.

## Types: Diffie-Hellman Keys and parameters

# dh_params()

(not exported)

    -type dh_params() :: [key_integer()].

    dh_params() = [P, G] | [P, G, MaxPrivateKeyBitLength]

# dh_private()

    -type dh_private() :: key_integer().

# dh_public()

    -type dh_public() :: key_integer().

Equivalent to `dh_private()`.

# ecdh_params()

(not exported)

    -type ecdh_params() :: ec_named_curve() | edwards_curve_dh() | ec_explicit_curve().

# ecdh_private()

(not exported)

    -type ecdh_private() :: key_integer().

Equivalent to `ecdh_params()`.

# ecdh_public()

(not exported)

    -type ecdh_public() :: key_integer().

Equivalent to `ecdh_params()`.

## Types: Digests and hash

# blake2()

(not exported)

    -type blake2() :: blake2b | blake2s.

# cmac_cipher_algorithm()

    -type cmac_cipher_algorithm() ::
              aes_128_cbc | aes_192_cbc | aes_256_cbc | aes_cbc | blowfish_cbc | des_cbc | des_ede3_cbc |
              rc2_cbc.

# compatibility_only_hash()

(not exported)

    -type compatibility_only_hash() :: md5 | md4.

The `compatibility_only_hash/0` algorithms are recommended only for compatibility with existing applications.

# dss_digest_type()

    -type dss_digest_type() :: sha1() | sha2().

# ecdsa_digest_type()

    -type ecdsa_digest_type() :: sha1() | sha2().

# hash_algorithm()

(not exported)

    -type hash_algorithm() ::
              sha1() | sha2() | sha3() | sha3_xof() | blake2() | ripemd160 | sm3 | compatibility_only_hash().

# hash_xof_algorithm()

(not exported)

    -type hash_xof_algorithm() :: sha3_xof().

# hmac_hash_algorithm()

    -type hmac_hash_algorithm() :: sha1() | sha2() | sha3() | sm3 | compatibility_only_hash().

# rsa_digest_type()

    -type rsa_digest_type() :: sha1() | sha2() | md5 | ripemd160.

# sha1()

    -type sha1() :: sha.

Equivalent to `blake2()`.

# sha2()

    -type sha2() :: sha224 | sha256 | sha384 | sha512 | sha512_224 | sha512_256.

Equivalent to `blake2()`.

# sha3()

    -type sha3() :: sha3_224 | sha3_256 | sha3_384 | sha3_512.

Equivalent to `blake2()`.

# sha3_xof()

(not exported)

    -type sha3_xof() :: shake128 | shake256.

Equivalent to `blake2()`.

## Types: Elliptic Curves

# ec_basis()

(not exported)

    -type ec_basis() ::
              {tpbasis, K :: non_neg_integer()} |
              {ppbasis, K1 :: non_neg_integer(), K2 :: non_neg_integer(), K3 :: non_neg_integer()} |
              onbasis.

Curve definition details.

# ec_characteristic_two_field()

(not exported)

    -type ec_characteristic_two_field() :: {characteristic_two_field, M :: integer(), Basis :: ec_basis()}.

Equivalent to `ec_basis()`.

# ec_curve()

(not exported)

    -type ec_curve() :: {A :: binary(), B :: binary(), Seed :: none | binary()}.

Parametric curve definition.

# ec_explicit_curve()

(not exported)

    -type ec_explicit_curve() ::
              {Field :: ec_field(),
               Curve :: ec_curve(),
               BasePoint :: binary(),
               Order :: binary(),
               CoFactor :: none | binary()}.

Equivalent to `ec_curve()`.

# ec_field()

(not exported)

    -type ec_field() :: ec_prime_field() | ec_characteristic_two_field().

Equivalent to `ec_curve()`.

# ec_named_curve()

    -type ec_named_curve() ::
              brainpoolP160r1 | brainpoolP160t1 | brainpoolP192r1 | brainpoolP192t1 | brainpoolP224r1 |
              brainpoolP224t1 | brainpoolP256r1 | brainpoolP256t1 | brainpoolP320r1 | brainpoolP320t1 |
              brainpoolP384r1 | brainpoolP384t1 | brainpoolP512r1 | brainpoolP512t1 | c2pnb163v1 |
              c2pnb163v2 | c2pnb163v3 | c2pnb176v1 | c2pnb208w1 | c2pnb272w1 | c2pnb304w1 | c2pnb368w1 |
              c2tnb191v1 | c2tnb191v2 | c2tnb191v3 | c2tnb239v1 | c2tnb239v2 | c2tnb239v3 | c2tnb359v1 |
              c2tnb431r1 | ipsec3 | ipsec4 | prime192v1 | prime192v2 | prime192v3 | prime239v1 |
              prime239v2 | prime239v3 | prime256v1 | secp112r1 | secp112r2 | secp128r1 | secp128r2 |
              secp160k1 | secp160r1 | secp160r2 | secp192k1 | secp192r1 | secp224k1 | secp224r1 |
              secp256k1 | secp256r1 | secp384r1 | secp521r1 | sect113r1 | sect113r2 | sect131r1 |
              sect131r2 | sect163k1 | sect163r1 | sect163r2 | sect193r1 | sect193r2 | sect233k1 |
              sect233r1 | sect239k1 | sect283k1 | sect283r1 | sect409k1 | sect409r1 | sect571k1 |
              sect571r1 | wtls1 | wtls10 | wtls11 | wtls12 | wtls3 | wtls4 | wtls5 | wtls6 | wtls7 | wtls8 |
              wtls9.

Equivalent to `edwards_curve_ed()`.

# ec_prime_field()

(not exported)

    -type ec_prime_field() :: {prime_field, Prime :: integer()}.

Equivalent to `ec_basis()`.

# edwards_curve_dh()

(not exported)

    -type edwards_curve_dh() :: x25519 | x448.

Equivalent to `edwards_curve_ed()`.

# edwards_curve_ed()

(not exported)

    -type edwards_curve_ed() :: ed25519 | ed448.

Note that some curves are disabled if FIPS is enabled.

## Types: Internal data types

# crypto_state()

    -opaque crypto_state()

Equivalent to `mac_state()`.

# hash_state()

    -opaque hash_state()

Equivalent to `mac_state()`.

# mac_state()

    -opaque mac_state()

Contexts with an internal state that should not be manipulated but passed between function calls.

## Types: Key Encapsulation Mechanism

# kem()

(not exported)

    -type kem() :: mlkem512 | mlkem768 | mlkem1024.

Key encapsulation mechanisms.

## Types: Keys

# key_integer()

(not exported)

    -type key_integer() :: integer() | binary().

Always `binary/0` when used as return value

## Types: Public Key Ciphers

# pk_encrypt_decrypt_algs()

(not exported)

    -type pk_encrypt_decrypt_algs() :: rsa.

Algorithms for public key encrypt/decrypt. Only RSA is supported.

# pk_encrypt_decrypt_opts()

    -type pk_encrypt_decrypt_opts() :: [rsa_opt()] | rsa_compat_opts().

Equivalent to `rsa_padding()`.

# rsa_compat_opts()

(not exported)

    -type rsa_compat_opts() :: [{rsa_pad, rsa_padding()}] | rsa_padding().

Those option forms are kept only for compatibility and should not be used in new code.

# rsa_opt()

(not exported)

    -type rsa_opt() ::
              {rsa_padding, rsa_padding()} |
              {signature_md, atom()} |
              {rsa_mgf1_md, sha} |
              {rsa_oaep_label, binary()} |
              {rsa_oaep_md, sha}.

Equivalent to `rsa_padding()`.

# rsa_padding()

(not exported)

    -type rsa_padding() :: rsa_pkcs1_padding | rsa_pkcs1_oaep_padding | rsa_x931_padding | rsa_no_padding.

Options for public key encrypt/decrypt. Only RSA is supported.

#### Warning

The RSA options are experimental.

The exact set of options and there syntax may be changed without prior notice.

## Types: Public Key Sign and Verify

# pk_sign_verify_algs()

(not exported)

    -type pk_sign_verify_algs() :: rsa | dss | ecdsa | eddsa | mldsa() | slh_dsa().

Algorithms for sign and verify.

# pk_sign_verify_opts()

    -type pk_sign_verify_opts() :: [rsa_sign_verify_opt()].

Equivalent to `rsa_sign_verify_padding()`.

# rsa_sign_verify_opt()

(not exported)

    -type rsa_sign_verify_opt() ::
              {rsa_padding, rsa_sign_verify_padding()} |
              {rsa_pss_saltlen, integer()} |
              {rsa_mgf1_md, sha2()}.

Equivalent to `rsa_sign_verify_padding()`.

# rsa_sign_verify_padding()

(not exported)

    -type rsa_sign_verify_padding() ::
              rsa_pkcs1_padding | rsa_pkcs1_pss_padding | rsa_x931_padding | rsa_no_padding.

Options for sign and verify.

#### Warning

The RSA options are experimental.

The exact set of options and there syntax may be changed without prior notice.

## Types: Public/Private Keys

# dss_private()

(not exported)

    -type dss_private() :: [key_integer()].

    dss_public() = [P, Q, G, Y]

Where P, Q and G are the dss parameters and Y is the public key.

    dss_private() = [P, Q, G, X]

Where P, Q and G are the dss parameters and X is the private key.

# dss_public()

(not exported)

    -type dss_public() :: [key_integer()].

Equivalent to `dss_private()`.

# ecdsa_params()

(not exported)

    -type ecdsa_params() :: ec_named_curve() | ec_explicit_curve().

# ecdsa_private()

(not exported)

    -type ecdsa_private() :: key_integer().

Equivalent to `ecdsa_params()`.

# ecdsa_public()

(not exported)

    -type ecdsa_public() :: key_integer().

Equivalent to `ecdsa_params()`.

# eddsa_params()

(not exported)

    -type eddsa_params() :: edwards_curve_ed().

# eddsa_private()

(not exported)

    -type eddsa_private() :: key_integer().

Equivalent to `eddsa_params()`.

# eddsa_public()

(not exported)

    -type eddsa_public() :: key_integer().

Equivalent to `eddsa_params()`.

# rsa_params()

(not exported)

    -type rsa_params() :: {ModulusSizeInBits :: integer(), PublicExponent :: key_integer()}.

    rsa_public() = [E, N]

    rsa_private() = [E, N, D] | [E, N, D, P1, P2, E1, E2, C]

Where E is the public exponent, N is public modulus and D is the private exponent. The longer key format contains redundant information that will make the calculation faster. P1 and P2 are first and second prime factors. E1 and E2 are first and second exponents. C is the CRT coefficient. The terminology is taken from RFC 3447.

# rsa_private()

(not exported)

    -type rsa_private() :: [key_integer()].

Equivalent to `rsa_params()`.

# rsa_public()

(not exported)

    -type rsa_public() :: [key_integer()].

Equivalent to `rsa_params()`.

# srp_comp_params()

(not exported)

    -type srp_comp_params() :: {user, srp_user_comp_params()} | {host, srp_host_comp_params()}.

Equivalent to `srp_host_comp_params()`.

# srp_gen_params()

(not exported)

    -type srp_gen_params() :: {user, srp_user_gen_params()} | {host, srp_host_gen_params()}.

Equivalent to `srp_host_comp_params()`.

# srp_host_comp_params()

(not exported)

    -type srp_host_comp_params() :: [binary() | atom()].

Where Verifier is `v`, Generator is `g` and Prime is`N`, DerivedKey is `X`, and Scrambler is `u` (optional will be generated if not provided) from SRP design Version = '3' | '6' | '6a'

# srp_host_gen_params()

(not exported)

    -type srp_host_gen_params() :: [binary() | atom() | list()].

Equivalent to `srp_host_comp_params()`.

# srp_private()

(not exported)

    -type srp_private() :: key_integer().

    srp_public() = key_integer()

Where is `A` or `B` from SRP design

    srp_private() = key_integer()

Where is `a` or `b` from SRP design

# srp_public()

(not exported)

    -type srp_public() :: key_integer().

Equivalent to `srp_private()`.

# srp_user_comp_params()

(not exported)

    -type srp_user_comp_params() :: [binary() | atom()].

Equivalent to `srp_host_comp_params()`.

# srp_user_gen_params()

(not exported)

    -type srp_user_gen_params() :: [binary() | atom() | list()].

Equivalent to `srp_host_comp_params()`.

## Types: Types for Engines

# engine_cmnd()

(not exported)

    -type engine_cmnd() :: {unicode:chardata(), unicode:chardata()}.

Pre and Post commands for engine_load/3 and /4.

# engine_key_ref()

(not exported)

    -type engine_key_ref() ::
              #{engine := engine_ref(), key_id := key_id(), password => password(), term() => term()}.

Equivalent to `engine_ref()`.

# engine_method_type()

(not exported)

    -type engine_method_type() ::
              engine_method_rsa | engine_method_dsa | engine_method_dh | engine_method_rand |
              engine_method_ecdh | engine_method_ecdsa | engine_method_ciphers | engine_method_digests |
              engine_method_store | engine_method_pkey_meths | engine_method_pkey_asn1_meths |
              engine_method_ec.

# engine_ref()

    -type engine_ref() :: term().

The result of a call to `engine_load/3`.

# key_id()

    -type key_id() :: string() | binary().

Identifies the key to be used. The format depends on the loaded engine. It is passed to the `ENGINE_load_(private|public)_key` functions in libcrypto.

# password()

    -type password() :: string() | binary().

The password of the key stored in an engine.

## Types

# crypto_integer()

(not exported)

    -type crypto_integer() :: binary() | integer().

# mldsa()

    -type mldsa() :: mldsa44 | mldsa65 | mldsa87.

# mldsa_private()

(not exported)

    -type mldsa_private() :: {seed | expandedkey, binary()}.

# mldsa_public()

(not exported)

    -type mldsa_public() :: binary().

# rand_cache_seed()

(not exported)

    -type rand_cache_seed() :: nonempty_improper_list(non_neg_integer(), binary()).

# slh_dsa()

    -type slh_dsa() ::
              slh_dsa_shake_128s | slh_dsa_shake_128f | slh_dsa_sha2_128s | slh_dsa_sha2_128f |
              slh_dsa_shake_192s | slh_dsa_shake_192f | slh_dsa_sha2_192s | slh_dsa_sha2_192f |
              slh_dsa_shake_256s | slh_dsa_shake_256f | slh_dsa_sha2_256s | slh_dsa_sha2_256f.

# slh_dsa_private()

(not exported)

    -type slh_dsa_private() :: binary().

# slh_dsa_public()

(not exported)

    -type slh_dsa_public() :: binary().

## Cipher API

# crypto_final(State)

(since OTP 23.0)

    -spec crypto_final(State) -> FinalResult when State :: crypto_state(), FinalResult :: binary().

Finalize a streaming encryptions or decryptions operation and delivers the final bytes of the final block.

The data returned from this function may be empty if no padding was enabled in `crypto_init/3` or `crypto_init/4`.

Uses the 3-tuple style for error handling.

# crypto_get_data(State)

(since OTP 23.0)

    -spec crypto_get_data(State) -> Result when State :: crypto_state(), Result :: map().

Return information about a `crypto_state/0`.

The information returned is a map, which currently contains at least:

- `size` - The number of bytes encrypted or decrypted so far.

- `padding_size` - After a call to `crypto_final/1` it contains the number of bytes padded. Otherwise 0.

- `padding_type` - The type of the padding as provided in the call to `crypto_init/3` or `crypto_init/4`.

- `encrypt` - Is `true` if encryption is performed. It is `false` otherwise.

Uses the 3-tuple style for error handling.

# crypto_init(Cipher, Key, FlagOrOptions)

(since OTP 22.0)

    -spec crypto_init(Cipher, Key, FlagOrOptions) -> State
                         when
                             Cipher :: cipher_no_iv(),
                             Key :: iodata(),
                             FlagOrOptions :: crypto_opts() | boolean(),
                             State :: crypto_state().

Initialize the state for a streaming encryption or decryption operation.

Equivalent to the call `crypto_init(Cipher, Key, <<>>, FlagOrOptions)`. It is intended for ciphers without an IV (nounce).

Uses the 3-tuple style for error handling.

# crypto_init(Cipher, Key, IV, FlagOrOptions)

(since OTP 22.0)

    -spec crypto_init(Cipher, Key, IV, FlagOrOptions) -> State
                         when
                             Cipher :: cipher_iv(),
                             Key :: iodata(),
                             IV :: iodata(),
                             FlagOrOptions :: crypto_opts(),
                             State :: crypto_state().

Initialize the state for a streaming encryptions or decryptions operation.

The returned state should be used as argument to `crypto_update/2` and `crypto_final/1` to do the actual encryption or decryption.

If `IV = <<>>`, no IV is used. This is intended for ciphers without an IV (nounce). See `crypto_init/3`.

For encryption, set the `FlagOrOptions` to `true` or `[{encrypt,true}]`. For decryption, set it to `false` or `[{encrypt,false}]`.

Padding could be enabled with the option {padding,Padding}. The cryptolib_padding enables `pkcs_padding` or no padding (`none`). The paddings `zero` or `random` fills the last part of the last block with zeroes or random bytes. If the last block is already full, nothing is added.

In decryption, the cryptolib_padding removes such padding, if present. The otp_padding is not removed - it has to be done elsewhere.

If padding is `{padding,none}` or not specified and the total data from all subsequent crypto_updates does not fill the last block fully, that last data is lost. In case of `{padding,none}` there will be an error in this case. If padding is not specified, the bytes of the unfilled block is silently discarded.

The actual padding is performed by `crypto_final/1`.

For blocksizes call `cipher_info/1`.

Uses the 3-tuple style for error handling.

See examples in the User's Guide.

# crypto_one_time(Cipher, Key, Data, FlagOrOptions)

(since OTP 22.0)

    -spec crypto_one_time(Cipher, Key, Data, FlagOrOptions) -> Result
                             when
                                 Cipher :: cipher_no_iv(),
                                 Key :: iodata(),
                                 Data :: iodata(),
                                 FlagOrOptions :: crypto_opts() | boolean(),
                                 Result :: binary().

Do a complete encrypt or decrypt of the full text.

As `crypto_one_time/5` but for ciphers without IVs.

Uses the 3-tuple style for error handling.

# crypto_one_time(Cipher, Key, IV, Data, FlagOrOptions)

(since OTP 22.0)

    -spec crypto_one_time(Cipher, Key, IV, Data, FlagOrOptions) -> Result
                             when
                                 Cipher :: cipher_iv(),
                                 Key :: iodata(),
                                 IV :: iodata(),
                                 Data :: iodata(),
                                 FlagOrOptions :: crypto_opts() | boolean(),
                                 Result :: binary().

Do a complete encrypt or decrypt of the full text.

Argument `Data` is the text to be encrypted or decrypted.

For encryption, set the `FlagOrOptions` to `true`. For decryption, set it to `false`. For setting other options, see `crypto_init/4`.

Uses the 3-tuple style for error handling.

See examples in the User's Guide.

# crypto_one_time_aead(State, IV, InText, AAD)

(since OTP 28.0)

    -spec crypto_one_time_aead(State, IV, InText, AAD) -> Result
                                  when
                                      State :: crypto_state(),
                                      IV :: iodata(),
                                      InText :: iodata(),
                                      AAD :: iodata(),
                                      Result :: EncryptResult | DecryptResult,
                                      EncryptResult :: binary(),
                                      DecryptResult :: binary() | error.

Do a complete encrypt or decrypt with an AEAD cipher of the full text.

Similar to 'crypto_one_time_aead/7' but uses the handle from 'crypto_one_time_aead_init/4'.

Appends the tag of the specified 'TagLength' to the end of the encrypted data, when doing encryption. Strips the tag from the end of 'InText' and verifies it when doing decryption.

# crypto_one_time_aead(Cipher, Key, IV, InText, AAD, EncFlag)

(since OTP 22.0)

    -spec crypto_one_time_aead(Cipher, Key, IV, InText, AAD, EncFlag :: true) -> Result
                                  when
                                      Cipher :: cipher_aead(),
                                      Key :: iodata(),
                                      IV :: iodata(),
                                      InText :: iodata(),
                                      AAD :: iodata(),
                                      Result :: EncryptResult,
                                      EncryptResult :: {OutCryptoText, OutTag},
                                      OutCryptoText :: binary(),
                                      OutTag :: binary().

Do a complete encrypt with an AEAD cipher of the full text with the default tag length.

Equivalent to `crypto_one_time_aead(Cipher, Key, IV, InText, AAD, TagLength, true)` where `TagLength` is the default tag length for the given `Cipher`.

# crypto_one_time_aead(Cipher, Key, IV, InText, AAD, TagOrTagLength, EncFlag)

(since OTP 22.0)

    -spec crypto_one_time_aead(Cipher, Key, IV, InText, AAD, TagOrTagLength, EncFlag) -> Result
                                  when
                                      Cipher :: cipher_aead(),
                                      Key :: iodata(),
                                      IV :: iodata(),
                                      InText :: iodata(),
                                      AAD :: iodata(),
                                      TagOrTagLength :: EncryptTagLength | DecryptTag,
                                      EncryptTagLength :: non_neg_integer(),
                                      DecryptTag :: iodata(),
                                      EncFlag :: boolean(),
                                      Result :: EncryptResult | DecryptResult,
                                      EncryptResult :: {OutCryptoText, OutTag},
                                      DecryptResult :: OutPlainText | error,
                                      OutCryptoText :: binary(),
                                      OutTag :: binary(),
                                      OutPlainText :: binary().

Do a complete encrypt or decrypt with an AEAD cipher of the full text.

For encryption, set the `EncryptFlag` to `true` and set the `TagOrTagLength` to the wanted size (in bytes) of the tag, that is, the tag length. If the default length is wanted, the `crypto_one_time_aead/6` form may be used.

For decryption, set the `EncryptFlag` to `false` and put the tag to be checked in the argument `TagOrTagLength`.

#### Warning

The length of the tag at decryption is not checked by the function. It is the caller's responsibility to ensure that the length of the tag matches the length of the tag used when the data was encrypted. Otherwise the decryption may succeed if the given tag only matches the start of the proper tag.

Additional Authentication Data (AAD) is plaintext data that will not be encrypted, but will be covered by authenticity protection. It should be provided through the `AAD` argument, but can be an empty binary as well (`<<>>`) if not needed. In that case, a plain AE (Authenticated Encryption) is performed instead of AEAD (Authenticated Encryption with Associated Data). This function only supports ciphers that can be used both with and without AAD.

Uses the 3-tuple style for error handling.

See examples in the User's Guide.

# crypto_one_time_aead_init(Cipher, Key, TagLength, EncFlag)

(since OTP 28.0)

    -spec crypto_one_time_aead_init(Cipher, Key, TagLength, EncFlag) -> Result
                                       when
                                           Cipher :: cipher_aead(),
                                           Key :: iodata(),
                                           TagLength :: non_neg_integer(),
                                           EncFlag :: boolean(),
                                           Result :: crypto_state().

Initializes AEAD cipher.

Similar to 'crypto_one_time_aead/7' but only does the initialization part, returns a handle that can be used with 'crypto_one_time_aead/4' serveral times.

# crypto_update(State, Data)

(since OTP 22.0)

    -spec crypto_update(State, Data) -> Result
                           when State :: crypto_state(), Data :: iodata(), Result :: binary().

Add data to a streaming encryption or decryption operation.

If the part is less than a number of full blocks, only the full blocks (possibly none) are encrypted or decrypted and the remaining bytes are saved to the next `crypto_update` operation. The `State` should be created with `crypto_init/3` or `crypto_init/4`.

Uses the 3-tuple style for error handling.

See examples in the User's Guide.

## Deprecated API

# enable_fips_mode(Enable)

(since OTP 21.1)
This function is deprecated. crypto:enable_fips_mode/1 is deprecated; use config parameter fips_mode.

    -spec enable_fips_mode(Enable) -> Result when Enable :: boolean(), Result :: boolean().

Enable or disable FIPs mode.

Argument `Enable` should be `true` to enable and `false` to disable FIPS mode. Returns `true` if the operation was successful or `false` otherwise.

Note that to enable FIPS mode successfully, OTP must be built with the configure option `--enable-fips`, and the underlying libcrypto must also support FIPS.

See also `info_fips/0`.

# start()

This function is deprecated. crypto:start/0 is deprecated; use application:start(crypto) instead.

    -spec start() -> ok | {error, Reason :: term()}.

Use `application:start(crypto)` instead.

#### Warning

This function does not work if FIPS mode is to be enabled. FIPS mode will be disabled even if configuration parameter `fips_mode` is set to `true`. Use `application:start(crypto)` instead.

# stop()

This function is deprecated. crypto:stop/0 is deprecated; use application:stop(crypto) instead.

    -spec stop() -> ok | {error, Reason :: term()}.

Use `application:stop(crypto)` instead.

## Engine API

# engine_add(Engine)

(since OTP 21.0.6)

    -spec engine_add(Engine) -> Result when Engine :: engine_ref(), Result :: ok | {error, Reason :: term()}.

Add the engine to OpenSSL's internal list.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

# engine_by_id(EngineId)

(since OTP 21.0.6)

    -spec engine_by_id(EngineId) -> Result
                          when
                              EngineId :: unicode:chardata(),
                              Result :: {ok, Engine :: engine_ref()} | {error, Reason :: term()}.

Get a reference to an already loaded engine with `EngineId`. An error tuple is returned if the engine cannot be unloaded.

The function raises a `error:badarg` if the parameter is in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

See also the chapter Engine Load in the User's Guide.

# engine_ctrl_cmd_string(Engine, CmdName, CmdArg)

(since OTP 20.2)

    -spec engine_ctrl_cmd_string(Engine, CmdName, CmdArg) -> Result
                                    when
                                        Engine :: term(),
                                        CmdName :: unicode:chardata(),
                                        CmdArg :: unicode:chardata(),
                                        Result :: ok | {error, Reason :: term()}.

Send ctrl commands to an OpenSSL engine.

This function is the same as calling `engine_ctrl_cmd_string/4` with `Optional` set to `false`.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

# engine_ctrl_cmd_string(Engine, CmdName, CmdArg, Optional)

(since OTP 20.2)

    -spec engine_ctrl_cmd_string(Engine, CmdName, CmdArg, Optional) -> Result
                                    when
                                        Engine :: term(),
                                        CmdName :: unicode:chardata(),
                                        CmdArg :: unicode:chardata(),
                                        Optional :: boolean(),
                                        Result :: ok | {error, Reason :: term()}.

Send ctrl commands to an OpenSSL engine.

`Optional` is a boolean argument that can relax the semantics of the function. If set to `true` it will only return failure if the ENGINE supported the given command name but failed while executing it, if the ENGINE does not support the command name it will simply return success without doing anything. In this case we assume the user is only supplying commands specific to the given ENGINE so we set this to `false`.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

# engine_get_all_methods()

(since OTP 20.2)

    -spec engine_get_all_methods() -> Result when Result :: [engine_method_type()].

Return a list of all possible engine methods.

May raise exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

See also the chapter Engine Load in the User's Guide.

# engine_get_id(Engine)

(since OTP 21.0.6)

    -spec engine_get_id(Engine) -> EngineId when Engine :: engine_ref(), EngineId :: unicode:chardata().

Return the ID for the engine, or an empty binary if there is no id set.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

# engine_get_name(Engine)

(since OTP 21.0.6)

    -spec engine_get_name(Engine) -> EngineName
                             when Engine :: engine_ref(), EngineName :: unicode:chardata().

Return the name (eg a description) for the engine, or an empty binary if there is no name set.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

# engine_list()

(since OTP 20.2)

    -spec engine_list() -> Result when Result :: [EngineId :: unicode:chardata()].

List the id's of all engines in OpenSSL's internal list.

It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

See also the chapter Engine Load in the User's Guide.

May raise exception `error:notsup` in case engine functionality is not supported by the underlying OpenSSL implementation.

# engine_load(EngineId, PreCmds, PostCmds)

(since OTP 20.2)

    -spec engine_load(EngineId, PreCmds, PostCmds) -> Result
                         when
                             EngineId :: unicode:chardata(),
                             PreCmds :: [engine_cmnd()],
                             PostCmds :: [engine_cmnd()],
                             Result :: {ok, Engine :: engine_ref()} | {error, Reason :: term()}.

Load an OpenSSL engine.

Loads the OpenSSL engine given by `EngineId` if it is available and intialize it. Returns `ok` and an engine handle, or if the engine cannot be loaded an error tuple is returned.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

See also the chapter Engine Load in the User's Guide.

# engine_register(Engine, EngineMethods)

(since OTP 25.1)

    -spec engine_register(Engine, EngineMethods) -> Result
                             when
                                 Engine :: engine_ref(),
                                 EngineMethods :: [engine_method_type()],
                                 Result :: ok | {error, Reason :: term()}.

Register engine to handle some type of methods, for example engine_method_digests.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

# engine_remove(Engine)

(since OTP 21.0.6)

    -spec engine_remove(Engine) -> Result
                           when Engine :: engine_ref(), Result :: ok | {error, Reason :: term()}.

Remove the engine from OpenSSL's internal list.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

# engine_unload(Engine)

(since OTP 20.2)

    -spec engine_unload(Engine) -> Result
                           when Engine :: engine_ref(), Result :: ok | {error, Reason :: term()}.

Unload an OpenSSL engine.

Unloads the OpenSSL engine given by `Engine`. An error tuple is returned if the engine cannot be unloaded.

The function raises a `error:badarg` if the parameter is in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

See also the chapter Engine Load in the User's Guide.

# engine_unregister(Engine, EngineMethods)

(since OTP 25.1)

    -spec engine_unregister(Engine, EngineMethods) -> Result
                               when
                                   Engine :: engine_ref(),
                                   EngineMethods :: [engine_method_type()],
                                   Result :: ok | {error, Reason :: term()}.

Unregister engine so it does not handle some type of methods.

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

# ensure_engine_loaded(EngineId, LibPath)

(since OTP 21.0.6)

    -spec ensure_engine_loaded(EngineId, LibPath) -> Result
                                  when
                                      EngineId :: unicode:chardata(),
                                      LibPath :: unicode:chardata(),
                                      Result :: {ok, Engine :: engine_ref()} | {error, Reason :: term()}.

Load a dynamic engine if not already done.

Loada the engine given by `EngineId` and the path to the dynamic library implementing the engine. An error tuple is returned if the engine cannot be loaded.

This function differs from the normal engine_load in the sense that it also add the engine id to OpenSSL's internal engine list. The difference between the first call and the following is that the first loads the engine with the dynamical engine and the following calls fetch it from the OpenSSL's engine list. All references that is returned are equal.

Use `engine_unload/1` function to remove the references. But remember that `engine_unload/1` just removes the references to the engine and not the tag in OpenSSL's engine list. That has to be done with the `engine_remove/1` function when needed (just called once, from any of the references you got).

The function raises a `error:badarg` if the parameters are in wrong format. It may also raise the exception `error:notsup` in case there is no engine support in the underlying OpenSSL implementation.

See also the chapter Engine Load in the User's Guide.

# pbkdf2_hmac(Digest, Pass, Salt, Iter, KeyLen)

(since OTP 24.2)

    -spec pbkdf2_hmac(Digest, Pass, Salt, Iter, KeyLen) -> Result
                         when
                             Digest :: sha | sha224 | sha256 | sha384 | sha512 | sha512_224 | sha512_256,
                             Pass :: binary(),
                             Salt :: binary(),
                             Iter :: pos_integer(),
                             KeyLen :: pos_integer(),
                             Result :: binary().

PKCS #5 PBKDF2 (Password-Based Key Derivation Function 2) in combination with HMAC.

Uses the 3-tuple style for error handling.

# privkey_to_pubkey(Type, EnginePrivateKeyRef)

(since OTP 20.2)

    -spec privkey_to_pubkey(Type, EnginePrivateKeyRef) -> PublicKey
                               when
                                   Type :: rsa | dss,
                                   EnginePrivateKeyRef :: engine_key_ref(),
                                   PublicKey :: rsa_public() | dss_public().

Fetch public key from a private key stored in an Engine.

The key must be of the type indicated by the Type parameter.

## Hash API

# hash(Type, Data)

(since OTP R15B02)

    -spec hash(Type, Data) -> Digest when Type :: hash_algorithm(), Data :: iodata(), Digest :: binary().

Compute a message digest.

Argument `Type` is the digest type and argument `Data` is the full message.

Uses the 3-tuple style for error handling.

# hash_final(State)

(since OTP R15B02)

    -spec hash_final(State) -> Digest when State :: hash_state(), Digest :: binary().

Finalize a streaming hash calculation.

Argument `State` as returned from the last call to hash_update. The size of `Digest` is determined by the type of hash function used to generate it.

Uses the 3-tuple style for error handling.

# hash_init(Type)

(since OTP R15B02)

    -spec hash_init(Type) -> State when Type :: hash_algorithm(), State :: hash_state().

Initialize the state for a streaming hash digest calculation.

Argument `Type` determines which digest to use. The returned state should be used as argument to `hash_update/2`.

Uses the 3-tuple style for error handling.

# hash_update(State, Data)

(since OTP R15B02)

    -spec hash_update(State, Data) -> NewState
                         when State :: hash_state(), NewState :: hash_state(), Data :: iodata().

Add data to a streaming digest calculation.

Update the digest using the given `Data` of any length.

Argument `State` must have been generated by hash_init or a previous call to this function.

Returns `NewState` that must be passed into the next call to `hash_update/2` or `hash_final/1`.

Uses the 3-tuple style for error handling.

# hash_xof(Type, Data, Length)

(since OTP 26.0)

    -spec hash_xof(Type, Data, Length) -> Digest
                      when
                          Type :: hash_xof_algorithm(),
                          Data :: iodata(),
                          Length :: non_neg_integer(),
                          Digest :: binary().

Compute a message digest for an `xof_algorithm`.

Argument `Type` is the type of digest, `Data` is the full text and `Length` is the digest length in bits.

Uses the 3-tuple style for error handling.

May raise exception `error:notsup` in case the chosen `Type` is not supported by the underlying libcrypto implementation.

## Key API

# compute_key(Type, OthersPublicKey, MyPrivateKey, Params)

(since OTP R16B01)

    -spec compute_key(Type, OthersPublicKey, MyPrivateKey, Params) -> SharedSecret
                         when
                             Type :: dh | ecdh | eddh | srp,
                             SharedSecret :: binary(),
                             OthersPublicKey :: dh_public() | ecdh_public() | srp_public(),
                             MyPrivateKey :: dh_private() | ecdh_private() | {srp_public(), srp_private()},
                             Params :: dh_params() | ecdh_params() | srp_comp_params().

Compute the shared secret from the private key and the other party's public key.

See also `public_key:compute_key/2`.

Uses the 3-tuple style for error handling.

# decapsulate_key(Type, MyPrivKey, EncapSecret)

(since OTP 28.1)

    -spec decapsulate_key(Type, MyPrivKey, EncapSecret) -> Secret
                             when
                                 Type :: kem(),
                                 MyPrivKey :: binary(),
                                 EncapSecret :: binary(),
                                 Secret :: binary().

Regenerate shared secret from encapsulated secret and private key.

Returns a shared secret for encryption/decryption by local party.

Supported encapsulation methods can be obtained with `supports(kems)`.

# encapsulate_key(Type, OthersPublicKey)

(since OTP 28.1)

    -spec encapsulate_key(Type, OthersPublicKey) -> {Secret, EncapSecret}
                             when
                                 Type :: kem(),
                                 OthersPublicKey :: binary(),
                                 Secret :: binary(),
                                 EncapSecret :: binary().

Generate encapsulated shared secret from the other party's public key.

Returns both a shared secret for encryption/decryption by local party and an encapsulated format of the same secret to be safely sent to the other party. With its private key, the other party can decapsulate the received secret (with `decapsulate_key/3` for example) to regenerate the same shared secret.

Supported encapsulation methods can be obtained with `supports(kems)`.

# generate_key(Type, Params)

(since OTP R16B01)

    -spec generate_key(Type, Params) -> {PublicKey, PrivKeyOut}
                          when
                              Type ::
                                  dh | ecdh | eddh | eddsa | rsa |
                                  mldsa() |
                                  mlkem512 | mlkem768 | mlkem1024 |
                                  slh_dsa() |
                                  srp,
                              PublicKey :: dh_public() | ecdh_public() | rsa_public() | srp_public(),
                              PrivKeyOut ::
                                  dh_private() |
                                  ecdh_private() |
                                  rsa_private() |
                                  {srp_public(), srp_private()},
                              Params ::
                                  dh_params() |
                                  ecdh_params() |
                                  eddsa_params() |
                                  rsa_params() |
                                  srp_gen_params() |
                                  [].

Equivalent to `generate_key/3`.

# generate_key(Type, Params, PrivKeyIn)

(since OTP R16B01)

    -spec generate_key(Type, Params, PrivKeyIn) -> {PublicKey, PrivKeyOut}
                          when
                              Type ::
                                  dh | ecdh | eddh | eddsa | rsa |
                                  mldsa() |
                                  mlkem512 | mlkem768 | mlkem1024 | srp |
                                  slh_dsa(),
                              PublicKey :: dh_public() | ecdh_public() | rsa_public() | srp_public(),
                              PrivKeyIn ::
                                  undefined |
                                  dh_private() |
                                  ecdh_private() |
                                  rsa_private() |
                                  {srp_public(), srp_private()},
                              PrivKeyOut ::
                                  dh_private() |
                                  ecdh_private() |
                                  rsa_private() |
                                  {srp_public(), srp_private()},
                              Params ::
                                  dh_params() |
                                  ecdh_params() |
                                  eddsa_params() |
                                  rsa_params() |
                                  srp_comp_params() |
                                  [].

Generate a public key.

See also `public_key:generate_key/1`.

Uses the 3-tuple style for error handling.

#### Note

If the linked version of cryptolib is OpenSSL 3.0

- and the `Type` is `dh` (diffie-hellman)
- and the parameter `P` (in `dh_params/0`) is one of the MODP groups (see RFC 3526)
- and the optional `MaxPrivateKeyBitLength` parameter (in `dh_params/0`) is present,

then the optional key length parameter must be at least 224, 256, 302, 352 and 400 for group sizes of 2048, 3072, 4096, 6144 and 8192, respectively.

## Legacy RSA Encryption API

# private_decrypt(Algorithm, CipherText, PrivateKey, Options)

(since OTP R16B01)

    -spec private_decrypt(Algorithm, CipherText, PrivateKey, Options) -> PlainText
                             when
                                 Algorithm :: pk_encrypt_decrypt_algs(),
                                 CipherText :: binary(),
                                 PrivateKey :: rsa_private() | engine_key_ref(),
                                 Options :: pk_encrypt_decrypt_opts(),
                                 PlainText :: binary().

Decrypt using a private key.

Decrypts the `CipherText`, encrypted with `public_encrypt/4` (or equivalent function) using the `PrivateKey`, and returns the plaintext (message digest). This is a low level signature verification operation used for instance by older versions of the SSL protocol. See also public_key:decrypt_private/2,3

Uses the 3-tuple style for error handling.

#### Warning

This is a legacy function, for security reasons do not use with rsa_pkcs1_padding.

# private_encrypt(Algorithm, PlainText, PrivateKey, Options)

(since OTP R16B01)

    -spec private_encrypt(Algorithm, PlainText, PrivateKey, Options) -> CipherText
                             when
                                 Algorithm :: pk_encrypt_decrypt_algs(),
                                 PlainText :: binary(),
                                 PrivateKey :: rsa_private() | engine_key_ref(),
                                 Options :: pk_encrypt_decrypt_opts(),
                                 CipherText :: binary().

Encrypt using a private key.

Encrypts the `PlainText` using the `PrivateKey` and returns the ciphertext. This is a low level signature operation used for instance by older versions of the SSL protocol. See also public_key:encrypt_private/2,3

Uses the 3-tuple style for error handling.

Public-key decryption using the private key. See also `crypto:private_decrypt/4`

#### Warning

This is a legacy function, for security reasons do not use with rsa_pkcs1_padding. For digital signatures use of `sign/4` together with `verify/5` is the prefered solution.

# public_decrypt(Algorithm, CipherText, PublicKey, Options)

(since OTP R16B01)

    -spec public_decrypt(Algorithm, CipherText, PublicKey, Options) -> PlainText
                            when
                                Algorithm :: pk_encrypt_decrypt_algs(),
                                CipherText :: binary(),
                                PublicKey :: rsa_public() | engine_key_ref(),
                                Options :: pk_encrypt_decrypt_opts(),
                                PlainText :: binary().

Decrypt using a public key.

Decrypts the `CipherText`, encrypted with `private_encrypt/4`(or equivalent function) using the `PublicKey`, and returns the plaintext (message digest). This is a low level signature verification operation used for instance by older versions of the SSL protocol. See also public_key:decrypt_public/2,3

Uses the 3-tuple style for error handling.

#### Warning

This is a legacy function, for security reasons do not use with rsa_pkcs1_padding. For digital signatures use of `verify/5` together with `sign/4` is the prefered solution.

# public_encrypt(Algorithm, PlainText, PublicKey, Options)

(since OTP R16B01)

    -spec public_encrypt(Algorithm, PlainText, PublicKey, Options) -> CipherText
                            when
                                Algorithm :: pk_encrypt_decrypt_algs(),
                                PlainText :: binary(),
                                PublicKey :: rsa_public() | engine_key_ref(),
                                Options :: pk_encrypt_decrypt_opts(),
                                CipherText :: binary().

Encrypt using a public key.

Encrypts the `PlainText` (message digest) using the `PublicKey` and returns the `CipherText`. This is a low level signature operation used for instance by older versions of the SSL protocol. See also public_key:encrypt_public/2,3

Uses the 3-tuple style for error handling.

#### Warning

This is a legacy function, for security reasons do not use together with rsa_pkcs1_padding.

## MAC API

# mac(Type, Key, Data)

(since OTP 22.1)

    -spec mac(Type :: poly1305, Key, Data) -> Mac when Key :: iodata(), Data :: iodata(), Mac :: binary().

Compute a `poly1305` MAC (Message Authentication Code).

Same as `mac(Type, undefined, Key, Data)`.

Uses the 3-tuple style for error handling.

# mac(Type, SubType, Key, Data)

(since OTP 22.1)

    -spec mac(Type, SubType, Key, Data) -> Mac
                 when
                     Type :: hmac | cmac | poly1305,
                     SubType :: hmac_hash_algorithm() | cmac_cipher_algorithm() | undefined,
                     Key :: iodata(),
                     Data :: iodata(),
                     Mac :: binary().

Compute a MAC (Message Authentication Code).

Argument `Type` is the type of MAC and `Data` is the full message.

`SubType` depends on the MAC `Type`:

- For `hmac` it is a hash algorithm, see Algorithm Details in the User's Guide.
- For `cmac` it is a cipher suitable for cmac, see Algorithm Details in the User's Guide.
- For `poly1305` it should be set to `undefined` or the mac/2 function could be used instead, see Algorithm Details in the User's Guide.

`Key` is the authentication key with a length according to the `Type` and `SubType`. The key length could be found with the `hash_info/1` (`hmac`) for and `cipher_info/1` (`cmac`) functions. For `poly1305` the key length is 32 bytes. Note that the cryptographic quality of the key is not checked.

The `Mac` result will have a default length depending on the `Type` and `SubType`. To set a shorter length, use `macN/4` or `macN/5` instead. The default length is documented in Algorithm Details in the User's Guide.

Uses the 3-tuple style for error handling.

# mac_final(State)

(since OTP 22.1)

    -spec mac_final(State) -> Mac when State :: mac_state(), Mac :: binary().

Finalize a streaming MAC operation.

Argument `State` is the state as returned by the last call to `mac_update/2`.

The `Mac` result will have a default length depending on the `Type` and `SubType` in the mac_init/2,3 call. To set a shorter length, use `mac_finalN/2` instead. The default length is documented in Algorithm Details in the User's Guide.

Uses the 3-tuple style for error handling.

# mac_finalN(State, MacLength)

(since OTP 22.1)

    -spec mac_finalN(State, MacLength) -> Mac
                        when State :: mac_state(), MacLength :: pos_integer(), Mac :: binary().

Finalize a MAC operation with a custom length.

Argument `State` is the state as returned by the last call to `mac_update/2`.

`Mac` will be a binary with at most `MacLength` bytes. Note that if `MacLength` is greater than the actual number of bytes returned from the underlying hash, the returned hash will have that shorter length instead.

The max `MacLength` is documented in Algorithm Details in the User's Guide.

Uses the 3-tuple style for error handling.

# mac_init(Type, Key)

(since OTP 22.1)

    -spec mac_init(Type :: poly1305, Key) -> State when Key :: iodata(), State :: mac_state().

Initialize a state for streaming `poly1305` MAC calculation.

Same as `mac_init(Type, undefined, Key)`.

Uses the 3-tuple style for error handling.

# mac_init(Type, SubType, Key)

(since OTP 22.1)

    -spec mac_init(Type, SubType, Key) -> State
                      when
                          Type :: hmac | cmac | poly1305,
                          SubType :: hmac_hash_algorithm() | cmac_cipher_algorithm() | undefined,
                          Key :: iodata(),
                          State :: mac_state().

Initialize the state for streaming MAC calculation.

`Type` determines which mac algorithm to use in the MAC operation.

`SubType` depends on the MAC `Type`:

- For `hmac` it is a hash algorithm, see Algorithm Details in the User's Guide.
- For `cmac` it is a cipher suitable for cmac, see Algorithm Details in the User's Guide.
- For `poly1305` it should be set to `undefined` or the mac/2 function could be used instead, see Algorithm Details in the User's Guide.

`Key` is the authentication key with a length according to the `Type` and `SubType`. The key length could be found with the `hash_info/1` (`hmac`) for and `cipher_info/1` (`cmac`) functions. For `poly1305` the key length is 32 bytes. Note that the cryptographic quality of the key is not checked.

The returned `State` should be used in one or more subsequent calls to `mac_update/2`. The MAC value is finally returned by calling `mac_final/1` or `mac_finalN/2`.

Uses the 3-tuple style for error handling.

See examples in the User's Guide.

# mac_update(State0, Data)

(since OTP 22.1)

    -spec mac_update(State0, Data) -> State
                        when Data :: iodata(), State0 :: mac_state(), State :: mac_state().

Add data to a streaming MAC calculation.

Update the MAC represented by `State0` using the given `Data` which could be of any length.

The `State0` is the State value originally from a MAC init function, that is `mac_init/2`, `mac_init/3` or the last call to `mac_update/2`. The value `State0` is returned unchanged by the function as a reference to a mutated internal state. Hence, it is not possible to branch off a data stream by reusing old states.

Uses the 3-tuple style for error handling.

# macN(Type, Key, Data, MacLength)

(since OTP 22.1)

    -spec macN(Type :: poly1305, Key, Data, MacLength) -> Mac
                  when Key :: iodata(), Data :: iodata(), Mac :: binary(), MacLength :: pos_integer().

Compute a `poly1305` MAC (Message Authentication Code) with a limited length.

Same as `macN(Type, undefined, Key, Data, MacLength)`.

Uses the 3-tuple style for error handling.

# macN(Type, SubType, Key, Data, MacLength)

(since OTP 22.1)

    -spec macN(Type, SubType, Key, Data, MacLength) -> Mac
                  when
                      Type :: hmac | cmac | poly1305,
                      SubType :: hmac_hash_algorithm() | cmac_cipher_algorithm() | undefined,
                      Key :: iodata(),
                      Data :: iodata(),
                      Mac :: binary(),
                      MacLength :: pos_integer().

Compute a MAC (Message Authentication Code) with a limited length.

Works like `mac/3` and `mac/4` but `MacLength` will limit the size of the resultant `Mac` to at most `MacLength` bytes. Note that if `MacLength` is greater than the actual number of bytes returned from the underlying hash, the returned hash will have that shorter length instead.

The max `MacLength` is documented in Algorithm Details in the User's Guide.

## Plug-In Generators

# rand_seed()

(since OTP 20.0)

    -spec rand_seed() -> rand:state().

Create a generator for `rand` and save it in the process dictionary.

Equivalent to `rand_seed_s/0` but also saves the returned state object (generator) in the process dictionary. That is, it is equivalent to `rand:seed(rand_seed_s())`.

See `rand:seed/1` and `rand_seed_s/0`.

#### Example

    _ = crypto:rand_seed(),
    IntegerValue = rand:uniform(42), % 1 .. 42
    FloatValue = rand:uniform().     % [0.0; 1.0)

### Note

Note that when using the process dictionary for cryptographically secure random numbers one has to ensure that no code called between initializing the generator and between generating numbers accidentally alters the generator state in the process dictionary.

The safe approach is to use the `rand` functions that do not use the process dictionary but take an explicit state argument: the ones suffixed `_s`. Thereby it is rather `rand_seed_s/0` that should be used instead of this function.

# rand_seed_alg(Alg)

(since OTP 21.0)

    -spec rand_seed_alg(Alg :: crypto | crypto_cache) -> {rand:alg_handler(), atom() | rand_cache_seed()}.

Create a generator for `rand` with specified algorithm, and save it in the process dictionary.

Equivalent `rand_seed_alg_s/1` but also saves the returned state object (generator) in the process dictionary. That is, it is equivalent to `rand:seed(rand_seed_alg_s(Alg))`.

See `rand:seed/1` and `rand_seed_alg_s/1`. Note the warning about the usage of the process dictionary in `rand_seed/0`.

#### Example

    _ = crypto:rand_seed_alg(crypto_cache),
    IntegerValue = rand:uniform(42), % 1 .. 42
    FloatValue = rand:uniform().     % [0.0; 1.0)

# rand_seed_alg(Alg, Seed)

(since OTP-22.0)

    -spec rand_seed_alg(Alg :: crypto_aes, Seed :: term()) ->
                           {rand:alg_handler(), atom() | rand_cache_seed()}.

Create and seed a generator for `rand` with specified algorithm, and save it in the process dictionary.

Equivalent to `rand_seed_alg_s/2` but also saves the returned state object (generator) in the process dictionary. That is, it is equivalent to `rand:seed(rand_seed_alg_s(Alg, Seed))`.

See `rand:seed/1` and `rand_seed_alg_s/2`. Note the warning about the usage of the process dictionary in `rand_seed/0`.

#### Example

    _ = crypto:rand_seed_alg(crypto_aes, "my seed"),
    IntegerValue = rand:uniform(42), % 1 .. 42
    FloatValue = rand:uniform(),     % [0.0; 1.0)
    _ = crypto:rand_seed_alg(crypto_aes, "my seed"),
    IntegerValue = rand:uniform(42), % Same values
    FloatValue = rand:uniform().     % again

# rand_seed_alg_s(Alg)

(since OTP 21.0)

    -spec rand_seed_alg_s(Alg :: crypto | crypto_cache) -> {rand:alg_handler(), atom() | rand_cache_seed()}.

Create a generator for `rand` with specified algorithm.

Create a state object (generator) for random number generation, which when used by the `rand` functions produce cryptographically strong random number.

See also `rand:seed_s/1` and for example `rand:uniform_s/2`.

If `Alg` is `crypto` this function is equivalent to `rand_seed_s/0`.

If `Alg` is `crypto_cache` the returned generator fetches random data with OpenSSL's `RAND_bytes` and caches it as 56 bit numbers which makes calculations fast on 64 bit machines.

#### Example

    S0 = crypto:rand_seed_alg_s(crypto_cache),
    {IntegerValue, S1} = rand:uniform(42, S0), % 1 .. 42
    {FloatValue, S2} = rand:uniform(S1).       % [0.0; 1.0)

May cause the `rand` functions using this state object to raise the exception `error:low_entropy` in case the random generator failed due to lack of secure "randomness".

The cache size can be changed from its default value using the crypto app's configuration parameter `rand_cache_size`.

#### Note

The state returned from this function cannot be used to get a reproducible random sequence as from the other `rand` functions, since that would not be cryptographically safe.

In fact when random data is cached some numbers may get reproduced occasionally, but this is unpredictable.

The only supported usage is to generate one distinct random sequence.

# rand_seed_alg_s(Alg, Seed)

(since OTP 22.0)

    -spec rand_seed_alg_s(Alg :: crypto_aes, Seed :: term()) ->
                             {rand:alg_handler(), atom() | rand_cache_seed()}.

Create and seed a generator for `rand` with specified algorithm.

Create a state object (generator) for random number generation, which when used by the `rand` functions produce cryptographically unpredictable random numbers

See also `rand:seed_s/1`, and for example `rand:uniform_s/2`. Compare to `rand_seed_alg/1`.

To get a long period the Xoroshiro928 generator from the `rand` module is used as a counter (with period 2^928 - 1) and the generator states are scrambled through AES to create 58-bit pseudo random values.

The result should be statistically completely unpredictable random values, since the scrambling is cryptographically strong and the period is ridiculously long. But the generated numbers are not to be regarded as cryptographically strong since there is no re-keying schedule, and since the sequence is repeated for the same seed.

- If you need cryptographically strong random numbers use `rand_seed_alg_s/1` with `Alg =:= crypto` or `Alg =:= crypto_cache`.
- If you need to be able to repeat the sequence use this function with `Alg =:= crypto_aes`.
- If you do not need the statistical quality of this function, there are faster algorithms in the `rand` module.

#### Example

    S0 = crypto:rand_seed_alg_s(crypto_aes, "my seed"),
    {IntegerValue, S1} = rand:uniform(42, S0), % 1 .. 42
    {FloatValue, S2 = rand:uniform(S1),        % [0.0; 1.0)
    S3 = crypto:rand_seed_alg_s(crypto_aes, "my seed"),
    {IntegerValue, S4} = rand:uniform(42, S3), % Same values
    {FloatValue, S5} = rand:uniform(S4).       % again

Thanks to the used generator the state object supports the `rand:jump/0,1` function with distance 2^512.

Numbers are generated in batches and cached for speed reasons. The cache size can be changed from its default value using the crypto app's configuration parameter `rand_cache_size`.

# rand_seed_s()

(since OTP 20.0)

    -spec rand_seed_s() -> rand:state().

Create a generator for `rand`.

Create a state object (generator) for random number generation, which when used by the `rand` functions produce cryptographically strong random numbers (based on OpenSSL's `BN_rand_range` function). See also `rand:seed_s/1`, and for example `rand:uniform_s/2`.

#### Example

    S0 = crypto:rand_seed_s(),
    {RandomInteger, S1} = rand:uniform_s(1000, S0).

May cause the `rand` functions using this state object to raise the exception `error:low_entropy` in case the random generator failed due to lack of secure "randomness".

#### Note

The state returned from this function cannot be used to get a reproducible random sequence as from the other `rand` functions, since that would not be cryptographically safe.

The only supported usage is to generate one distinct random sequence.

## Random API

# rand_seed(Seed)

(since OTP 17.0)

    -spec rand_seed(binary()) -> ok.

Mixes in the bytes of the given binary into the internal state of OpenSSL's random number generator.

This calls the RAND_seed function from OpenSSL. Only use this if the system you are running on does not have enough "randomness" built in. Normally this is when `strong_rand_bytes/1` or a generator from `rand_seed_alg_s/1` raises `error:low_entropy`.

# rand_uniform/2

This function is deprecated. crypto:rand_uniform/2 is deprecated; use strong_rand_range/1 instead.

    -spec rand_uniform(crypto_integer(), crypto_integer()) -> crypto_integer().

Generate a random integer number.

The interval is `From =< N < To`. Uses the `crypto` library pseudo-random number generator. `To` must be larger than `From`.

#### Note

This function is deprecated because it originally used the OpenSSL method BN_pseudo_rand_range that was not cryptographically strong and could not run out of entropy. That behaviour changed in OpenSSL and this function cannot be fixed without making it raise `error:low_entropy`, which is not backwards compatible.

Instead, use `strong_rand_range(To - From) + From`

Be aware of the possible `error:low_entropy` exception.

# strong_rand_bytes(N)

(since OTP R14B03)

    -spec strong_rand_bytes(N :: non_neg_integer()) -> binary().

Generate bytes with randomly uniform values 0..255.

Returns the result in a binary with `N` bytes.

Uses a cryptographically secure PRNG seeded and periodically mixed with operating system provided entropy. By default this is the `RAND_bytes` method from OpenSSL.

May raise exception `error:low_entropy` in case the random generator failed due to lack of secure "randomness".

# strong_rand_range/1

(since OTP 28.3)

    -spec strong_rand_range(Range :: pos_integer()) -> N :: non_neg_integer();
                           (Range :: binary()) -> N :: binary().

Generate a random integer in a specified range.

The returned random integer is in the interval is `0` =< `N` < `Range`.

Uses the `crypto` library random number generator BN_rand_range.

If the `Range` argument is a `pos_integer/0` the return value is a `non_neg_integer/0`. If the `Range` argument is a positive integer in a `binary/0`, the return value is a non-negative integer in a `binary/0`.

May raise exception `error:low_entropy` in case the random generator failed due to lack of secure "randomness".

## Sign/Verify API

# sign(Algorithm, DigestType, Msg, Key)

(since OTP R16B01)

    -spec sign(Algorithm, DigestType, Msg, Key) -> Signature
                  when
                      Algorithm :: pk_sign_verify_algs(),
                      DigestType :: rsa_digest_type() | dss_digest_type() | ecdsa_digest_type() | none,
                      Msg :: iodata() | {digest, iodata()},
                      Key ::
                          rsa_private() |
                          dss_private() |
                          [ecdsa_private() | ecdsa_params()] |
                          [eddsa_private() | eddsa_params()] |
                          mldsa_private() |
                          slh_dsa_private() |
                          engine_key_ref(),
                      Signature :: binary().

Equivalent to `sign/5`.

# sign(Algorithm, DigestType, Msg, Key, Options)

(since OTP 20.1)

    -spec sign(Algorithm, DigestType, Msg, Key, Options) -> Signature
                  when
                      Algorithm :: pk_sign_verify_algs(),
                      DigestType :: rsa_digest_type() | dss_digest_type() | ecdsa_digest_type() | none,
                      Msg :: iodata() | {digest, iodata()},
                      Key ::
                          rsa_private() |
                          dss_private() |
                          [ecdsa_private() | ecdsa_params()] |
                          [eddsa_private() | eddsa_params()] |
                          mldsa_private() |
                          slh_dsa_private() |
                          engine_key_ref(),
                      Options :: pk_sign_verify_opts(),
                      Signature :: binary().

Create a digital signature.

The msg is either the binary "cleartext" data to be signed or it is the hashed value of "cleartext" i.e. the digest (plaintext).

Algorithm `dss` can only be used together with digest type `sha`.

Uses the 3-tuple style for error handling.

See also `public_key:sign/3`.

# verify(Algorithm, DigestType, Msg, Signature, Key)

(since OTP R16B01)

    -spec verify(Algorithm, DigestType, Msg, Signature, Key) -> Result
                    when
                        Algorithm :: pk_sign_verify_algs(),
                        DigestType :: rsa_digest_type() | dss_digest_type() | ecdsa_digest_type() | none,
                        Msg :: iodata() | {digest, iodata()},
                        Signature :: binary(),
                        Key ::
                            rsa_public() |
                            dss_public() |
                            [ecdsa_public() | ecdsa_params()] |
                            [eddsa_public() | eddsa_params()] |
                            mldsa_public() |
                            slh_dsa_public() |
                            engine_key_ref(),
                        Result :: boolean().

Equivalent to `verify/6`.

# verify(Algorithm, DigestType, Msg, Signature, Key, Options)

(since OTP 20.1)

    -spec verify(Algorithm, DigestType, Msg, Signature, Key, Options) -> Result
                    when
                        Algorithm :: pk_sign_verify_algs(),
                        DigestType :: rsa_digest_type() | dss_digest_type() | ecdsa_digest_type() | none,
                        Msg :: iodata() | {digest, iodata()},
                        Signature :: binary(),
                        Key ::
                            rsa_public() |
                            dss_public() |
                            [ecdsa_public() | ecdsa_params()] |
                            [eddsa_public() | eddsa_params()] |
                            mldsa_public() |
                            slh_dsa_public() |
                            engine_key_ref(),
                        Options :: pk_sign_verify_opts(),
                        Result :: boolean().

Verify a digital signature.

The msg is either the binary "cleartext" data to be signed or it is the hashed value of "cleartext" i.e. the digest (plaintext).

Algorithm `dss` can only be used together with digest type `sha`.

Uses the 3-tuple style for error handling.

See also `public_key:verify/4`.

## Utility Functions

# bytes_to_integer(Bin)

(since OTP R16B01)

    -spec bytes_to_integer(binary()) -> integer().

Convert binary representation, of an integer, to an Erlang integer.

# cipher_info(Type)

(since OTP 22.0)

    -spec cipher_info(Type) -> Result
                         when
                             Type :: cipher(),
                             Result ::
                                 #{key_length := integer(),
                                   iv_length := integer(),
                                   block_size := integer(),
                                   mode := CipherModes,
                                   type := undefined | integer(),
                                   prop_aead := boolean()},
                             CipherModes ::
                                 undefined | cbc_mode | ccm_mode | cfb_mode | ctr_mode | ecb_mode |
                                 gcm_mode | ige_mode | ocb_mode | ofb_mode | wrap_mode | xts_mode.

Get information about a cipher algorithm.

Returns a map with information about block size, key length, IV length, aead support and possibly other properties of the cipher algorithm in question.

#### Note

The ciphers `aes_cbc`, `aes_cfb8`, `aes_cfb128`, `aes_ctr`, `aes_ecb`, `aes_gcm` and `aes_ccm` has no keylength in the `Type` as opposed to for example `aes_128_ctr`. They adapt to the length of the key provided in the encrypt and decrypt function. Therefore it is impossible to return a valid keylength in the map.

Always use a `Type` with an explicit key length,

For a list of supported cipher algorithms, see supports(ciphers).

# ec_curve(CurveName)

(since OTP 17.0)

    -spec ec_curve(CurveName) -> ExplicitCurve
                      when CurveName :: ec_named_curve(), ExplicitCurve :: ec_explicit_curve().

Return the defining parameters of a elliptic curve.

# ec_curves()

(since OTP 17.0)

    -spec ec_curves() -> [EllipticCurve]
                       when EllipticCurve :: ec_named_curve() | edwards_curve_dh() | edwards_curve_ed().

Return all supported named elliptic curves.

# exor(Bin1, Bin2)

    -spec exor(iodata(), iodata()) -> binary().

Perform bit-wise XOR (exclusive or) on the data supplied.

The two byte sequences mus be of equal length.

# hash_equals(BinA, BinB)

(since OTP 25.0)

    -spec hash_equals(BinA, BinB) -> Result when BinA :: binary(), BinB :: binary(), Result :: boolean().

Compare two binaries in constant time, such as results of HMAC computations.

Returns true if the binaries are identical, false if they are of the same length but not identical. The function raises an `error:badarg` exception if the binaries are of different size.

# hash_info(Type)

(since OTP 22.0)

    -spec hash_info(Type) -> Result
                       when
                           Type :: hash_algorithm(),
                           Result :: #{size := integer(), block_size := integer(), type := integer()}.

Get information about a hash algorithm.

Returns a map with information about block_size, size and possibly other properties of the hash algorithm in question.

For a list of supported hash algorithms, see supports(hashs).

# info()

(since OTP 24.2)

    -spec info() ->
                  #{compile_type := normal | debug | valgrind | asan,
                    cryptolib_version_compiled := string() | undefined,
                    cryptolib_version_linked := string(),
                    link_type := dynamic | static,
                    otp_crypto_version := string(),
                    fips_provider_available => boolean(),
                    fips_provider_buildinfo => string()}.

Get information about crypto and the OpenSSL backend.

Returns a map with information about the compilation and linking of crypto.

Example:

    1> crypto:info().
    #{compile_type => normal,
      cryptolib_version_compiled => "OpenSSL 3.0.0 7 sep 2021",
      cryptolib_version_linked => "OpenSSL 3.0.0 7 sep 2021",
      link_type => dynamic,
      otp_crypto_version => "5.0.2",
      fips_provider_available => true,
      fips_provider_buildinfo => "3.0.0"}
    2>

More association types than documented may be present in the map. Some of the associations (like fips) may be absent if not supported.

# info_fips()

(since OTP 20.0)

    -spec info_fips() -> not_supported | not_enabled | enabled.

Get information about the operating status of FIPS.

Returns the FIPS operating status of crypto and the underlying libcrypto library. If crypto was built with FIPS support this can be either `enabled` (when running in FIPS mode) or `not_enabled`. For other builds this value is always `not_supported`.

See configuration parameter fips_mode about how to enable FIPS mode.

#### Warning

In FIPS mode all non-FIPS compliant algorithms are disabled and raise exception `error:notsup`. Check supports(ciphers) that in FIPS mode returns the restricted list of available algorithms.

# info_lib()

    -spec info_lib() -> [{Name, VerNum, VerStr}]
                      when Name :: binary(), VerNum :: integer(), VerStr :: binary().

Get the name and version of the libraries used by crypto.

`Name` is the name of the library. `VerNum` is the numeric version according to the library's own versioning scheme. `VerStr` contains a text variant of the version.

    > info_lib().
    [{<<"OpenSSL">>,269484095,<<"OpenSSL 1.1.0c  10 Nov 2016"">>}]

#### Note

From OTP R16 the numeric version represents the version of the OpenSSL header files (`openssl/opensslv.h`) used when crypto was compiled. The text variant represents the libcrypto library used at runtime. In earlier OTP versions both numeric and text was taken from the library.

# mod_pow(N, P, M)

(since OTP R16B01)

    -spec mod_pow(N, P, M) -> Result
                     when
                         N :: binary() | integer(),
                         P :: binary() | integer(),
                         M :: binary() | integer(),
                         Result :: binary() | error.

Compute the function `N^P mod M`.

# supports(Type)

(since OTP 22.0)

    -spec supports(Type) -> Support
                      when
                          Type :: hashs | ciphers | kems | public_keys | macs | curves | rsa_opts,
                          Support :: Hashs | Ciphers | KEMs | PKs | Macs | Curves | RSAopts,
                          Hashs ::
                              [sha1() |
                               sha2() |
                               sha3() |
                               sha3_xof() |
                               blake2() |
                               ripemd160 |
                               compatibility_only_hash()],
                          Ciphers :: [cipher()],
                          KEMs :: [kem()],
                          PKs :: [rsa | dss | ecdsa | dh | ecdh | eddh | ec_gf2m],
                          Macs :: [hmac | cmac | poly1305],
                          Curves :: [ec_named_curve() | edwards_curve_dh() | edwards_curve_ed()],
                          RSAopts :: [rsa_sign_verify_opt() | rsa_opt()].

Get which crypto algorithms that are supported by the underlying libcrypto library.

See `hash_info/1` and `cipher_info/1` for information about the hash and cipher algorithms.