Php/docs/function.hash-pbkdf2
hash_pbkdf2
(PHP 5 >= 5.5.0, PHP 7)
hash_pbkdf2 — Generate a PBKDF2 key derivation of a supplied password
Description
hash_pbkdf2
( string $algo
, string $password
, string $salt
, int $iterations
[, int $length
= 0
[, bool $binary
= FALSE
]] ) : string
Parameters
algo
Name of selected hashing algorithm (i.e.
md5
,sha256
,haval160,4
, etc..) See hash_algos() for a list of supported algorithms.password
The password to use for the derivation.
salt
The salt to use for the derivation. This value should be generated randomly.
iterations
The number of internal iterations to perform for the derivation.
length
The length of the output string. If
binary
isTRUE
this corresponds to the byte-length of the derived key, ifbinary
isFALSE
this corresponds to twice the byte-length of the derived key (as every byte of the key is returned as two hexits).If
0
is passed, the entire output of the supplied algorithm is used.binary
When set to
TRUE
, outputs raw binary data.FALSE
outputs lowercase hexits.
Return Values
Returns a string containing the derived key as lowercase hexits unless
binary
is set to TRUE
in which case the raw
binary representation of the derived key is returned.
Errors/Exceptions
An E_WARNING
will be raised if the algorithm is
unknown, the iterations
parameter is less than or
equal to 0
, the length
is less
than 0
or the salt
is too long
(greater than INT_MAX
- 4
).
Changelog
Version | Description |
---|---|
7.2.0 | Usage of non-cryptographic hash functions (adler32, crc32, crc32b, fnv132, fnv1a32, fnv164, fnv1a64, joaat) was disabled. |
Examples
Example #1 hash_pbkdf2() example, basic usage
<?php$password = "password";$iterations = 1000;// Generate a random IV using openssl_random_pseudo_bytes()// random_bytes() or another suitable source of randomness$salt = openssl_random_pseudo_bytes(16);$hash = hash_pbkdf2("sha256", $password, $salt, $iterations, 20);echo $hash;?>
The above example will output something similar to:
120fb6cffcf8b32c43e7
Notes
Caution
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.
See Also
- crypt() - One-way string hashing
- password_hash() - Creates a password hash
- hash() - Generate a hash value (message digest)
- hash_algos() - Return a list of registered hashing algorithms
- hash_init() - Initialize an incremental hashing context
- hash_hmac() - Generate a keyed hash value using the HMAC method
- hash_hmac_file() - Generate a keyed hash value using the HMAC method and the contents of a given file
- openssl_pbkdf2() - Generates a PKCS5 v2 PBKDF2 string