有没有不变的mycrypt模式吗？

Question

I am using mcrypt to store credit card numbers in a table. I am also using the same credit card numbers to check if the user has already applied the coupon code.

The problem that I am facing is that the mcrypt string always changes, when the user posts their credit card number on the checkout page.

Is there an mcrypt method that does not change the string each time?

By the way, I am using codeigniter's encryption class to cipher the credit card numbers

Any help would be really appricated

Answer 1

Notice: storing and processing credit card data is not recommended providing you know little about security and encryption

The function you are using outputs different string but you can check them if the input was indentical.

When it comes to functions that return "same strings" everytime, you can use SHA256 hashing function:

<?php
   $string = "123";
   $hash = hash( 'sha256', $string );
   $user_input = "123";

   if(hash( 'sha256', $user_input ) == $hash){
        echo "Correct credit card number";
   } else {
        echo "Did not find a match";
   }
?>

Read more about the hash() method here