Which password hashing algorithm is best for PHP logins: SHA1, MD5, SHA256, or bcrypt?

Comparing SHA1, MD5, and SHA256 for PHP Logins

When developing a PHP login system, it's crucial to choose a secure password hashing algorithm. SHA1, MD5, and SHA256 are common options, but significant differences exist among them.

Security:

Neither SHA1 nor MD5 is considered secure for modern applications. They have been compromised by various attacks, making them vulnerable to brute-force and collision-based methods. SHA256, while stronger than its predecessors, is not immune to attacks.

Salt Usage:

Using a salt is essential for enhancing password security. A salt is a random value appended to the password before hashing. This makes precomputed attacks more difficult, as the attacker must guess both the password and the salt. All three algorithms support the use of a salt.

Recommended Approach:

Instead of using SHA1, MD5, or SHA256, it's highly recommended to employ bcrypt. Bcrypt has been specifically designed for password hashing and addresses the weaknesses of the aforementioned algorithms. It utilizes a more complex key derivation function and supports adjustable cost parameters to optimize performance and security.

PHP 5.5 Implementation:

PHP 5.5 introduced password_hash() and password_verify() functions for bcrypt operations:

<code class="php">$hash = password_hash($password, PASSWORD_DEFAULT, ['cost' => 12]);
if (password_verify($password, $hash)) {
    // Password matches, log in the user
}</code>

Caveats of bcrypt:

• bcrypt truncates passwords longer than 72 characters.
• bcrypt truncates after any NUL characters.

To mitigate these caveats, it's advisable to use a third-party library designed for password handling, such as ZendCrypt or PasswordLock. These libraries provide robust implementations with advanced security features.

Conclusion:

When implementing PHP logins, the preferred option is bcrypt due to its superior security measures compared to SHA1, MD5, and SHA256. Remember to follow best practices such as using salts and storing password hashes securely in your database.

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