sodium_crypto_pwhash_scryptsalsa208sha256

Derives a key from a password, using scrypt

Description

string sodium_crypto_pwhash_scryptsalsa208sha256(
    int $length,
    #[\SensitiveParameter]string $password,
    string $salt,
    int $opslimit,
    int $memlimit
)

This is the scrypt counterpart to sodium_crypto_pwhash.

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).

Parameters

length: The length of the password hash to generate, in bytes.
password: The password to generate a hash for.
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 random_bytes, and have a length of at least SODIUM_CRYPTO_PWHASH_SCRYPTSALSA208SHA256_SALTBYTES bytes.
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: SODIUM_CRYPTO_PWHASH_SCRYPTSALSA208SHA256_OPSLIMIT_INTERACTIVE and SODIUM_CRYPTO_PWHASH_SCRYPTSALSA208SHA256_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: SODIUM_CRYPTO_PWHASH_SCRYPTSALSA208SHA256_MEMLIMIT_INTERACTIVE and SODIUM_CRYPTO_PWHASH_SCRYPTSALSA208SHA256_MEMLIMIT_SENSITIVE. Typically these should be paired with the matching opslimit values.

Return Values

A string of bytes of the desired length.