Privacy Policy

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    <h1>Privacy Policy</h1>
    <p>
        QuantumVault is free, open-source, zero-knowledge software. This page
        describes what the software itself collects and, more importantly,
        what it is structurally <em>unable</em> to access, regardless of the
        intentions of whoever operates a given instance ("the operator").
        Because each instance is independently self-hosted under the AGPLv3,
        the operator of the instance you are using is the party responsible
        for its data practices, retention periods, and any applicable local
        law; this page describes the guarantees built into the software
        itself, which apply to every instance.
    </p>

    <h2>What the Operator Can Never See</h2>
    <ul>
        <li>
            <strong>Your password:</strong> authentication uses SRP-6a, a
            zero-knowledge proof. Your password is never transmitted, in any
            form, to the server.
        </li>
        <li>
            <strong>Your private keys:</strong> your hybrid ML-KEM-768 +
            X25519 key pair is generated in your browser and stored only as a
            blob encrypted with a key derived from your password
            (PBKDF2-SHA256, 600,000 iterations). The server only ever
            receives that encrypted blob.
        </li>
        <li>
            <strong>Message and file contents:</strong> messages and files
            are encrypted client-side with AES-256-GCM before upload. The
            server stores and relays opaque ciphertext only.
        </li>
    </ul>

    <h2>Information the Software Collects</h2>
    <p>
        To provide the service, an instance necessarily stores some
        information:
    </p>
    <ul>
        <li>
            <strong>Account information:</strong> the email address (and any
            other identifier, such as a phone number, if the registration
            form requires it) used to create and recover access to your
            account, plus your SRP verifier (a value that proves you know
            your password without revealing it).
        </li>
        <li>
            <strong>Encrypted payloads:</strong> your encrypted private key
            blob, encrypted files, and encrypted messages, all opaque to the
            server.
        </li>
        <li>
            <strong>Public keys:</strong> your ML-KEM-768 and X25519 public
            keys, which are not secret and are needed by other users to
            encrypt data to you.
        </li>
        <li>
            <strong>Operational metadata:</strong> standard web server logs
            (such as IP addresses, timestamps, and request metadata), and
            message/file timestamps and sizes, which are not protected by
            end-to-end encryption and may be visible to the operator of an
            instance.
        </li>
    </ul>

    <h2>How This Information Is Used</h2>
    <p>The data described above is used only to:</p>
    <ul>
        <li>Authenticate you and maintain your session</li>
        <li>Store and relay your encrypted data so you can retrieve it</li>
        <li>Operate, secure, and maintain the instance</li>
        <li>Comply with legal obligations applicable to the operator</li>
    </ul>
    <p>
        Because QuantumVault is AGPLv3, the source code that processes this
        data is publicly available, so anyone can verify these claims
        directly rather than relying on a promise.
    </p>

    <h2>Your Rights</h2>
    <p>
        You may request to view, correct, or delete the account metadata held
        by an instance (email/identifiers, account status, and stored
        ciphertext) at any time, by contacting the administrator of that
        instance. Because content is end-to-end encrypted, deleting your
        account and its stored ciphertext is equivalent to deleting your
        data &mdash; no one, including the operator, can decrypt it
        afterward. No instance sells your data, and the software contains no
        mechanism for monetizing or sharing your data with third parties.
    </p>

    <h2>Changes to This Policy</h2>
    <p>
        This page describes the privacy properties of the QuantumVault
        software itself and is updated alongside the software. Operators of
        individual instances may publish additional, instance-specific
        privacy information (for example, their jurisdiction, log retention
        period, or contact details) separately.
    </p>

    <p><strong>Last Updated:</strong> June 2026</p>
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