DES is one of the most used encryption methods.
Strange is that there is not much you can find on using it with the arduino.
There are other encryption techniques such as AES etc used which can be seen here.
So i had a bash at making a DES implementation an the arduino. No hacking or cracking just a simple decoder and encoder. Dont ask what its for. It is possible therefore.
You will find all the bits and pieces from the DES algorithm easily back in this code. Below you can find an extract from the printout of the program.
Each of the steps are output to the screen so you can follow all the steps. Here you can see the final round of the decryption giving the plaintext or decrypted key.
DES counts backwards from round 16 to 1 in the decryption mode so that is why you see round 1 (the last round) here.
There is a very good excel version of such a process which visualizes the whole process that can be downloaded from the bottom of the link.
I have used this as the basis to make other DES based algorithms such as the one used by Meteotime.
Here you can find my other arduino projects.