**Course Title:** Modern PHP Development: Best Practices and Advanced Techniques **Section Title:** Security in PHP: Best Practices **Topic:** Best practices for securing passwords using hashing (password_hash and password_verify) ### Introduction to Password Security Storing passwords securely is crucial for protecting user accounts from unauthorized access. The most common approach to storing passwords securely is through hashing. Hashing transforms the original password into an unreadable sequence of characters, making it virtually impossible for attackers to access the original password even if they gain access to the hashed version. ### The Problem with Traditional Hashing Methods Traditional hashing methods, such as MD5 and SHA-1, are no longer recommended for password storage due to known vulnerabilities and their inability to withstand modern computing power. Modern password cracking tools can quickly crack these hashes, compromising user security. ### Introduction to password_hash and password_verify To counter these issues, PHP 5.5 introduced two new functions: `password_hash` and `password_verify`. These functions provide a secure and efficient way to hash and verify passwords. **`password_hash`:** * This function creates a new password hash using a strong hashing algorithm (by default, `bcrypt`, but can be changed to other algorithms like `argon2i`). * It allows you to choose the hashing algorithm and customize its options (e.g., cost factor). * It generates a random salt that is embedded into the hash. **`password_verify`:** * This function verifies that a password matches the provided hash. * It takes into account the hashing algorithm, salt, and other parameters used when creating the hash. ### Using password_hash and password_verify Here's a step-by-step example of how to use these functions: ```php // Create a new hash $password = 'mysecretpassword'; $hash = password_hash($password, PASSWORD_DEFAULT); // Verify the password if (password_verify($password, $hash)) { echo 'Password verified!'; } else { echo 'Error: Password verification failed!'; } ``` In this example: 1. We first create a new hash using `password_hash`, specifying the password and the default hashing algorithm (`PASSWORD_DEFAULT`, which currently defaults to `bcrypt`). 2. We then use `password_verify` to verify the password against the hash. This function returns `true` if the password matches the hash and `false` otherwise. ### Understanding PASSWORD_DEFAULT `PASSWORD_DEFAULT` is a constant in PHP that represents the best hashing algorithm available at the time of writing. Using `PASSWORD_DEFAULT` as the hashing algorithm allows you to future-proof your application's password storage by automatically taking advantage of the most secure algorithm supported by the PHP version your application is running on. If you want to use an alternative hashing algorithm (e.g., `argon2i`), you can specify it as the second argument: ```php $hash = password_hash($password, PASSWORD_ARGON2I); ``` However, it is recommended to use `PASSWORD_DEFAULT` unless you have specific requirements that cannot be met by using it. ### Choosing the Cost Factor The cost factor is an optional argument for `password_hash` that controls how computationally expensive the hashing algorithm should be. A higher cost factor means that password generation and verification will take longer. However, this does not significantly impact performance in most applications since passwords are typically updated and verified relatively infrequently. ```php $hash = password_hash($password, PASSWORD_DEFAULT, ['cost' => 10]); ``` ### Password Migration It's essential to update passwords when transitioning from a weaker hashing algorithm to a stronger one. PHP provides a straightforward way to migrate passwords using the `password_needs_rehash` function: ```php $hash = 'existing_hash'; $password = 'new_password'; if (password_needs_rehash($hash, PASSWORD_DEFAULT)) { // Update the password hash $newHash = password_hash($password, PASSWORD_DEFAULT); // Store the $newHash in your database // Do not forget to update your password in all locations (session, cookies etc) // so the user doesn't lose access } ``` ### Key Takeaways * Use `password_hash` to generate new password hashes. * Use `password_verify` to verify passwords against existing hashes. * Prefer `PASSWORD_DEFAULT` for the hashing algorithm. * Use `password_needs_rehash` to determine whether an existing hash needs updating. ### External Resources For further reading, consider consulting the official PHP documentation: * `password_hash`: <https://www.php.net/manual/en/function.password-hash.php> * `password_verify`: <https://www.php.net/manual/en/function.password-verify.php> * `password_needs_rehash`: <https://www.php.net/manual/en/function.password-needs-rehash.php> ### Conclusion By following the guidelines outlined in this topic and using the `password_hash` and `password_verify` functions effectively, you can significantly improve the security of your PHP applications by protecting user passwords. No need to comment the above lecture just follow and observe the links. --- The next topic we will cover will be from PHP Frameworks: Introduction to Laravel or Symfony, we will cover **Overview of modern PHP frameworks and why they are used.**