(PHP 5 >= 5.5.0, PHP 7, PHP 8)
hash_pbkdf2 — Generate a PBKDF2 key derivation of a supplied password
algo
Name of selected hashing algorithm (e.g. "sha256").
For a list of supported algorithms see hash_hmac_algos().
Note:
Non-cryptographic hash functions are not allowed.
passwordThe password to use for the derivation.
saltThe salt to use for the derivation. This value should be generated randomly.
iterationsThe number of internal iterations to perform for the derivation.
length
The length of the output string. If binary
is true this corresponds to the byte-length of the derived key, if
binary is false this corresponds to twice the
byte-length of the derived key (as every byte of the key is returned as
two hexits).
If 0 is passed, the entire output of the supplied
algorithm is used.
binary
When set to true, outputs raw binary data. false outputs lowercase
hexits.
options
An array of options for the various hashing algorithms.
Currently, only the "seed" key is
supported by the MurmurHash variants.
Returns a string containing the derived key as lowercase hexits unless
binary is set to true in which case the raw
binary representation of the derived key is returned.
Throws a ValueError exception if the algorithm is
unknown, the iterations parameter is less than or
equal to 0, the length is less
than 0 or the salt is too long
(greater than INT_MAX - 4).
| Version | Description |
|---|---|
| 8.0.0 |
Now throws a ValueError exception on error.
Previously, false was returned and an E_WARNING
message was emitted.
|
| 7.2.0 | Usage of non-cryptographic hash functions (adler32, crc32, crc32b, fnv132, fnv1a32, fnv164, fnv1a64, joaat) was disabled. |
Example #1 hash_pbkdf2() example, basic usage
<?php
$password = "password";
$iterations = 600000;
// Generate a cryptographically secure random salt using random_bytes()
$salt = random_bytes(16);
$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);
var_dump($hash);
// for raw binary, the $length needs to be halved for equivalent results
$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 10, true);
var_dump(bin2hex($hash));?>The above example will output something similar to:
string(20) "120fb6cffcf8b32c43e7" string(20) "120fb6cffcf8b32c43e7"
The PBKDF2 method can be used for hashing passwords for storage. However, it
should be noted that password_hash() or
crypt() with CRYPT_BLOWFISH are
better suited for password storage.