Can I Decrypt Passwords Hashed With PHP\'s `password_hash()` Function?

Password Decryption in PHP: Unraveling the Password Puzzle

Introduction
Encrypting passwords is crucial for safeguarding user data. However, decrypting encrypted passwords can be a dilemma. This article addresses the commonly asked question of how to decrypt a password hash in PHP, using the password_hash() function.

Background
The password_hash() function in PHP implements the bcrypt one-way hashing algorithm. Bcrypt hashes are designed to be computationally expensive to brute-force attack. This means that it is impractical to reverse the hashing process and recover the original password.

Question
A developer needs to validate user passwords against encrypted passwords stored in a database. The passwords were encrypted using the password_hash() function. They want to know if there is a way to decrypt the encrypted passwords to compare them to the user input.

Answer
Decryption is not possible with bcrypt hashes. Instead, we use password_verify() to verify whether a password matches a stored hash:

<code class="php">if (password_verify($inputPassword, $hash)) {
    // Password is valid
} else {
    // Invalid password
}</code>

In your specific case, modify the SQL query to retrieve the user record based on the username only:

<code class="sql">$sql_script = 'SELECT * FROM USERS WHERE username=?';</code>

Then, use a similar technique to verify the password in PHP.

Additional Considerations
It is essential to use parameterized queries to prevent SQL injection vulnerabilities. Here is an example of how to parameterize the above query:

<code class="php">$stmt = $conn->prepare($sql_script);
$stmt->bind_param('s', $username);
$stmt->execute();</code>

By using parameterization, you protect against malicious input that could harm your database.

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