encoder.m decoder.m

Simple and instructive implementation of symmetric-key encryption and decryption.

Tristan Ursell
Encoder - dual level
Jan 2017
Includes two functions -- an encoder and decoder which together form a private symmetric key encryption system, with message-length masking.
[enc_message,key]=encoder(raw_message);
[enc_message,key]=encoder(raw_message,key);
[enc_message,key,msg_length]=encoder(raw_message,key);
'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
time stamp.

** - must be the same between encoder and decoder