The openssl_pbkdf2() function is an inbuilt function in PHP that implements the Password-Based Key Derivation Function 2 (PBKDF2) algorithm provided by the OpenSSL library. The algorithm is designed to be slow and computationally intensive, making it resistant to brute-force attacks.
Syntax:
openssl_pbkdf2(
string $password,
string $salt,
int $key_length,
int $iterations,
string $digest_algo = "sha1" )
: string|false
Parameters: This function accepts five parameters that are described below:
- $password: The password that the key should be derived from.
- $salt: A random salt value that should be used to help make the derived key unique.
- $key_length: The length (in bytes) of the derived key.
- $iterations: The number of iterations to use when deriving the key. More iterations will make the algorithm slower but also more secure.
- $digest_algo: The digest algorithm to use when deriving the key. This should be one of the supported OpenSSL digest algorithms, such as “sha256” or “sha512”.
Return Value: The return value of openssl_pbkdf2() is a binary string containing the derived key. If failure, it will return “false”.
Example 1: The following example demonstrates the openssl_pbkdf2() function.
PHP
<?php $password = "this@ismypassword55839459144595"; // Saved hash from a previous run $savedHash = "MjY4YjRkZDc1YzAzNzYzZGMwZDEzYjI3NmVlM2ZkNTE="; $decodedHash = base64_decode($savedHash); if (openssl_pbkdf2($password, $decodedHash, 32, 10000, "sha256") === $decodedHash) { echo "Password is valid."; } else { echo "Password is invalid."; } ?> |
Output
Password is invalid.
Example 2: The following example demonstrates the openssl_pbkdf2() function.
PHP
<?php $userID = 'user123'; $deviceID = 'device456'; $secretKey = openssl_random_pseudo_bytes(32); $salt = $userID . $deviceID; $iterations = 50000; $keyLength = 64; $secureToken = openssl_pbkdf2($secretKey, $salt, $keyLength, $iterations, 'sha512'); // Display the secure token echo "Secure Token: " . base64_encode($secureToken) . "\n"; ?> |
Output:
Secure Token: LWL+RuQr+TmOysJt8CBrKu5yC8vk2f9aMBH9y1xK82Nz4dDd88dd+8QqssBgoMDnGD9D5kTcmAlldzz7hUStjw==
Reference: https://www.php.net/manual/en/function.openssl-pbkdf2.php
