Edit Report a Bug

    hash_hkdf

    (PHP 7 >= 7.1.2, PHP 8)

    hash_hkdf — Generate a HKDF key derivation of a supplied key input

    Beschreibung

    hash_hkdf(
        string $algo,
        string $key,
        int $length = 0,
        string $info = "",
        string $salt = ""
    ): string

    Parameter-Liste

    algo

    Name of selected hashing algorithm (i.e. "sha256", "sha512", "haval160,4", etc..) See hash_algos() for a list of supported algorithms.

    Hinweis:

    Non-cryptographic hash functions are not allowed.

    key

    Input keying material (raw binary). Cannot be empty.

    length

    Desired output length in bytes. Cannot be greater than 255 times the chosen hash function size.

    If length is 0, the output length will default to the chosen hash function size.

    info

    Application/context-specific info string.

    salt

    Salt to use during derivation.

    While optional, adding random salt significantly improves the strength of HKDF.

    Rückgabewerte

    Returns a string containing a raw binary representation of the derived key (also known as output keying material - OKM).

    Fehler/Exceptions

    Throws a ValueError exception if key is empty, algo is unknown/non-cryptographic, length is less than 0 or too large (greater than 255 times the size of the hash function).

    Changelog

    Version Beschreibung
    8.0.0 Now throws a ValueError exception on error. Previously, false was returned and an E_WARNING message was emitted.

    Beispiele

    Beispiel #1 hash_hkdf() example

    <?php
    // Generate a random key, and salt to strengthen it during derivation.
    $inputKey = random_bytes(32);
    $salt = random_bytes(16);

    // Derive a pair of separate keys, using the same input created above.
    $encryptionKey = hash_hkdf('sha256', $inputKey, 32, 'aes-256-encryption', $salt);
    $authenticationKey = hash_hkdf('sha256', $inputKey, 32, 'sha-256-authentication', $salt);

    var_dump($encryptionKey !== $authenticationKey); // bool(true)
    ?>

    The above example produces a pair of separate keys, suitable for creation of an encrypt-then-HMAC construct, using AES-256 and SHA-256 for encryption and authentication respectively.

    Siehe auch

    add a note add a note

    User Contributed Notes 1 note

    up
    1
    landers dot robert at gmail dot com
    2 years ago
    Make sure the info parameter contains random elements.

    From: https://soatok.blog/2021/11/17/understanding-hkdf/
    add a note add a note
    To Top