Why is mcrypt_encrypt() putting binary characters at the end of my string?

Question

Here is a PHP demo script that encrypts and decrypts data:

Answer 1

The returned string is padded out to fill n * blocksize bytes using the null character \0 so that is why you are seeing the extra data.

If you run $card_nbr_decrypted= rtrim($card_nbr_decrypted, "\0"); it should return the actual data.