PHP

Hash Passwords With PHP 5.5

Almost every PHP developer would have to build an application that relies on a user login. This will involve the user of the website having a Username and Password which is stored in the database so they can login into your website.

As passwords are stored in the database it is important that you hash these passwords before you store them in the database. A password hash is a one way encryption of a string, so you won't be able to decrypt this to find out what the password is.

You should never store a password in the database without hashing it first, if a third party gets access to your database they will be able to get hold of all the password's or your users. Some users will use the same password for all their accounts such as email, so it is important that you protect your users by hashing the passwords.

Password hashing is a one way encryption so when you are comparing the string with the password entered by the user you will need to hash the password they entered and compare this string with the hashed password, if they match then the password is correct.

Ways Of Hashing Passwords

A while ago it was common to find people hashing passwords by using these functions.

But these functions are not recommended to use when you are hashing passwords. This is because of the way these functions work, you can easily create a script to use brute force on this function to return a string that matches another md5() string. Using these functions it doesn't matter how ever many times you pass a string into this function it will also return the same hashed password, so if two users have the same password and one user's password gets hacked then the other user's password is too.

These functions are fine to use for other hashing but it is not recommended for passwords.

Instead of using these function you should be using crypt() or the hash() function, the complexity of these functions means that they are slower to run than the other md5() and sha1() functions. This means that the output from a brute force attack will take much longer to run than using the md5() function.

Another benefit of using the crypt() function is that you can pass a second parameter of a salt. A salt is an encrypted string that is added to the password during hashing, it is a way of adding additional data to the string which will make the hash harder to crack.

Password Hashing Using 5.5

In PHP version 5.5 password hashing functions were introduced into the core giving you access to use 4 functions to use when hashing passwords and verifying a password.

  • password_get_info — Returns information about the given hash
  • password_hash — Creates a password hash
  • password_needs_rehash — Checks if the given hash matches the given options
  • password_verify — Verifies that a password matches a hash

The two important functions to understand are the password_hash() and the password_verify().

Password_hash Function

The password_hash function will create the hashed password from a string, It takes 3 parameters, the first is the string to hash, second is the algorithm you want to use to hash the password and the third are additional options like salt to pass into the function.

$options = [
    'cost' => 11,
    'salt' => mcrypt_create_iv(22, MCRYPT_DEV_URANDOM),
];
$hashed_password = password_hash( $string, PASSWORD_DEFAULT, $options );

The default hashing algorithm password_hash uses is currently bcrypt, note that this could change in the future as newer encryption algorithms are added into PHP.

The third parameter allows you to add a salt to the password, if one is not provided then PHP will generate a random salt to use for each password generated. It is actually recommended to not generate a salt for this function but allow PHP to generate the salt for you.

Password Hash

Password_verify Function

This function is used to make sure that the string password and the string hashed password match and will return a boolean TRUE if the passwords match.

$matched = password_verify( $password, $hashed_password );

Using just these two function you can now easily create a user login section which generates secure passwords you can store in the database and match when the user logins in.

Password Verify

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