Encoder - dual level
Includes two functions -- an encoder and decoder which together form a private symmetric key encryption system, with message-length masking.
'raw_message' is the original message in ASCII text to be encoded.
'key'** is an integer or char-integer less than 2^32 that will be used as
random number generator seed and serves as the cipher key. If no key is
provided, the script will generate one automatically using the current
** - must be the same between encoder and decoder