How Can I Securely Hash Passwords Using bcrypt in PHP?

Using bcrypt for Password Hashing in PHP

Introduction

bcrypt is a powerful hashing algorithm designed specifically for securely storing passwords. It employs a technique called key stretching, making it computationally intensive and difficult to crack compared to other basic hashing algorithms like MD5 or SHA.

How bcrypt Works

bcrypt uses the Eksblowfish algorithm, which derives its strength from a combination of Blowfish encryption and additional key scheduling techniques. It requires a salt (a random string) to generate a hashed password. The salt ensures that each hash is unique even if the same password is used multiple times.

Implementation in PHP

Using PHP >= 5.5-DEV:
PHP >= 5.5 provides built-in password hashing functions:

• password_hash() generates a bcrypt hash with a parameter to specify the number of rounds (strength).
• password_verify() verifies a user-provided password against an existing hash.

Using PHP >= 5.3.7, < 5.5-DEV:
Install the compatibility library from GitHub for the same functionality as PHP >= 5.5.

Using PHP < 5.3.7: (DEPRECATED)
Consider using crypt() function with the CRYPT_BLOWFISH constant to generate bcrypt hashes. However, this method is deprecated and not recommended for PHP versions above 5.3.7.

Example Usage

PHP >= 5.5-DEV:

<?php
$hash = password_hash('password', PASSWORD_DEFAULT);
$isVerified = password_verify('password', $hash);
?>

PHP >= 5.3.7, < 5.5-DEV:

hash('password');
$isVerified = $bcrypt->verify('password', $hash);
?>
Benefits of bcrypt


High Security: bcrypt's key stretching makes it resistant to brute-force attacks.

Uniqueness: The use of salts ensures that each hash is unique for the same password.

Verifiability: Stored hashes can be easily verified with a user-provided password.

Conclusion
bcrypt is a highly secure and industry-standard algorithm for hashing passwords in PHP. Its key stretching and salt-based design provide exceptional protection against unauthorized access. It is recommended to use the built-in PHP functions or a reputable PHP bcrypt implementation like the compatibility library for optimal security.
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