Updated 2012-10-02 - Version ZF 2.0.3

Secure Password Storing

Zend\Crypt\Password stores a user’s password in a secure way using dedicated adapters like the bcrypt algorithm.

The example below shows how to use the bcrypt algorithm to store a user’s password:

use Zend\Crypt\Password\Bcrypt;

$bcrypt = new Bcrypt()
$securePass = $bcrypt->create('user password');

The output of the create() method is the encrypted password. This value can then be stored in a repository like a database. Classic hashing mechanisms like MD5 or SHA are not considered secure anymore (read this post to know why).

To verify if a given password is valid against a bcrypt value you can use the verify() method. Example time:

use Zend\Crypt\Password\Bcrypt;

$bcrypt = new Bcrypt();
$securePass = 'the stored bcrypt value';
$password = 'the password to check';

if ($bcrypt->verify($password, $securePass)) {
    echo "The password is correct! \n";
} else {
    echo "The password is NOT correct.\n";

By default, the Zend\Crypt\Password\Bcrypt class uses a value of 14 for bcrypts cost parameter. The cost parameter is an integer between 4 to 31. A greater value means longer execution time for bcrypt, thus more secure against brute force or dictionary attacks.

If you want to change the cost parameter of the bcrypt algorithm you can use the setCost() method.


Bcrypt with non-ASCII passwords (8-bit characters)

The bcrypt implementation used by PHP < 5.3.7 can contains a security flaw if the password uses 8-bit characters (here’s the security report). The impact of this bug was that most (but not all) passwords containing non-ASCII characters with the 8th bit set were hashed incorrectly, resulting in password hashes incompatible with those of OpenBSD’s original implementation of bcrypt. This security flaw has been fixed starting from PHP 5.3.7 and the prefix used in the output was changed to ‘$2y$’ in order to put evidence on the correctness of the hash value. If you are using PHP < 5.3.7 with 8-bit passwords, the Zend\Crypt\Password\Bcrypt throws an exception suggesting to upgrade to PHP 5.3.7+ or use only 7-bit passwords.


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