Having Trouble?

Lots of people of have emailed me because they are having problems decrypting data using another package. So this page provides some recommendations, some things to test against, and some proof that the Javascript DES version does actually work.

Firstly, I recommend you try encrypting and decrypting using the examples below to see if you get the same results. If your results bear no relation at all to the examples below check you are using the same mode, same algorithm (eg single or triple DES) and same input vector (for CBC mode). If only the last part of your result is wrong, check you are using the same padding method.

Encrypted data might also become corrupted in transport (eg from the client to server) or when displayed on the screen (see first example below). For these reasons I convert the strings to and from hexidecimal. (Note that this conversion is not done automatically by the algorithm. You have to do it explicitly before or after running DES.) So also check that your package uses hexidecimal (and not base64 or some other method), check whether or not it needs the 0x at the beginning of the hexidecimal string, and check that the hexidecimal conversion works the same (for example "test string" should convert to 0x7465737420737472696e67).

Luckily this server has the PHP mcrypt library available, so I can show (below) that this Javascript DES (and the PHP translation) do in fact produce the correct results. The mcrypt library pads with null bytes, so that is the padding used below. You can also test the Javascript implementation with other keys and messages.

Single DES Encryption in ECB mode

Code used to call the above

Single DES Decryption in ECB mode

Single DES Encryption in CBC mode

Single DES Decryption in CBC mode

Triple DES Encryption in ECB mode

Triple DES Decryption in ECB mode

Triple DES Encryption in CBC mode

Triple DES Decryption in CBC mode

Code used to call the above

Standard ANSI test for single DES in ECB Mode