Why Do Password Hash Values Differ in PHP and How to Verify Them?

Understanding Different Password Hash Values in PHP

In securing login systems, password hashing is often employed to safeguard user credentials. However, encountering different hashed values each time can raise concerns.

Issue:

Attempting to hash passwords with password_hash(), the generated values vary, and subsequent verification via password_verify() fails.

Explanation:

password_hash() intentionally returns unique values each time due to its use of randomization for security purposes. This ensures that each password's corresponding hash is unique, making it much more difficult to attack or compromise user accounts.

Verification:

To properly verify hashed passwords, the original unhashed password and the stored hash ($dbpassword) should be used as inputs for password_verify(). The function is responsible for comparing the unhashed password with the hashed version, validating whether they match.

Security Enhancement:

To further enhance security, consider increasing the hashing cost passed as an argument to password_hash(). A higher cost, such as 15 in the example below, results in more iterations of the hashing algorithm, making it computationally more intensive and increasing the resistance to brute force attacks.

<code class="php">$password = password_hash($password4, PASSWORD_DEFAULT, ['cost' => 15]);</code>

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