Block.des_encryptThe DES block cipher, in encryption mode. The string argument is the key; its length must be 8 bytes.
transform src spos dst dpos encrypts or decrypts one block of data. The input data is read from byte array src at positions spos, ..., spos + blocksize - 1, and the output data is stored in byte array dst at positions dpos, ..., dpos + blocksize - 1.