Block.des_encrypt
The 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
.