sodium_crypto_pwhash

sodium_crypto_pwhash

Derive a key from a password, using Argon2

string **sodium_crypto_pwhash** int $length string $password string $salt int $opslimit int $memlimit int $algo

This function provides low-level access to libsodium's crypto_pwhash key derivation function. Unless you have specific reason to use this function, you should use or functions instead. sodium_crypto_pwhash_str``password_hash

A common reason to use this particular function is to derive the seeds for cryptographic keys from a password and salt, and then use these seeds to generate the actual keys needed for some purpose (e.g. ). sodium_crypto_sign_detached

length ; The length of the password hash to generate, in bytes. int

password ; The password to generate a hash for. string

salt A salt to add to the password before hashing. The salt should be unpredictable, ideally generated from a good random number source such as , and have a length of exactly bytes. random_bytes``SODIUM_CRYPTO_PWHASH_SALTBYTES

opslimit Represents a maximum amount of computations to perform. Raising this number will make the function require more CPU cycles to compute a key. There are some constants available to set the operations limit to appropriate values depending on intended use, in order of strength: , and . SODIUM_CRYPTO_PWHASH_OPSLIMIT_INTERACTIVE``SODIUM_CRYPTO_PWHASH_OPSLIMIT_MODERATE``SODIUM_CRYPTO_PWHASH_OPSLIMIT_SENSITIVE

memlimit The maximum amount of RAM that the function will use, in bytes. There are constants to help you choose an appropriate value, in order of size: , , and . Typically these should be paired with the matching values. SODIUM_CRYPTO_PWHASH_MEMLIMIT_INTERACTIVE``SODIUM_CRYPTO_PWHASH_MEMLIMIT_MODERATE``SODIUM_CRYPTO_PWHASH_MEMLIMIT_SENSITIVE``opslimit

algo A number indicating the hash algorithm to use. By default (the currently recommended algorithm, which can change from one version of libsodium to another), or explicitly using , representing the Argon2id algorithm version 1.3. int``SODIUM_CRYPTO_PWHASH_ALG_DEFAULT``SODIUM_CRYPTO_PWHASH_ALG_ARGON2ID13

Returns the derived key. The return value is a binary string of the hash, not an ASCII-encoded representation, and does not contain additional information about the parameters used to create the hash, so you will need to keep that information if you are ever going to verify the password in future. Use to avoid needing to do all that. sodium_crypto_pwhash_str

Voorbeeld: example

<?php
//Need to keep the salt if we're ever going to be able to check this password
$salt = random_bytes(SODIUM_CRYPTO_PWHASH_SALTBYTES);
//Using bin2hex to keep output readable
echo bin2hex(
    sodium_crypto_pwhash(
        16, // == 128 bits
        'password',
        $salt,
        SODIUM_CRYPTO_PWHASH_OPSLIMIT_INTERACTIVE,
        SODIUM_CRYPTO_PWHASH_MEMLIMIT_INTERACTIVE,
        SODIUM_CRYPTO_PWHASH_ALG_ARGON2ID13
    )
);
?>

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