sodium_crypto_pwhash
(PHP 7 >= 7.2.0, PHP 8)
sodium_crypto_pwhash — Derive a key from a password, using Argon2
Description
int
$length,string
$password,string
$salt,int
$opslimit,int
$memlimit,int
$algo = SODIUM_CRYPTO_PWHASH_ALG_DEFAULT): string
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 sodium_crypto_pwhash_str() or password_hash() functions instead.
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 -
int; The length of the password hash to generate, in bytes.
-
password -
string; 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_SALTBYTESbytes. -
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_OPSLIMIT_INTERACTIVE,SODIUM_CRYPTO_PWHASH_OPSLIMIT_MODERATEandSODIUM_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:
SODIUM_CRYPTO_PWHASH_MEMLIMIT_INTERACTIVE,SODIUM_CRYPTO_PWHASH_MEMLIMIT_MODERATE, andSODIUM_CRYPTO_PWHASH_MEMLIMIT_SENSITIVE. Typically these should be paired with the matchingopslimitvalues. -
algo -
int A number indicating the hash algorithm to use. By default
SODIUM_CRYPTO_PWHASH_ALG_DEFAULT(the currently recommended algorithm, which can change from one version of libsodium to another), or explicitly usingSODIUM_CRYPTO_PWHASH_ALG_ARGON2ID13, representing the Argon2id algorithm version 1.3.
Return Values
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 sodium_crypto_pwhash_str() to avoid needing to do all that.
Examples
Example #1 sodium_crypto_pwhash() 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
)
);
?>
The above example will output something similar to:
a18f346ba57992eb7e4ae6abf3fd30ee
