Re: Tasking and Concurrent Programming Using Multiple Ada Programs.

[Robert Eachus <rieachus@comcast.net>]

On Saturday, April 29, 2017 at 12:08:57 PM UTC-4, Austin Obyrne wrote:

> I have come over from sci crypt group to ask your advice on an
> encryption concept...

Sigh!  See if you can get a copy of The Codebreakers by David Kahn from your library.  It was initially published in the 1960s, and there is a revised edition from 1997 that I haven't seen.   Of course, just about anything I did during my career is covered in one added chapter. There are other books I could recommend as introductions to cryptography, but none covering material more recent than WWII.  Modern cryptography, including public-key cryptography and FIPS standard algorithms are all very math intensive, mostly Number Theory.

The system you are attempting sounds like a variation on polyalphabetic substitution.  The US Government kept the "index of coincidence" a secret during WWII, and that was the major weakness of polyalphabetic systems.  Once you find the IC, you can solve the system as n more standard systems.  Most of the FIPS systems, such as AES, uses the previous state of the system as part of the key for the next (256) bits.

Oh, and don't try to implement AES in Ada, without some particular need.  It can be done, but most CPU chips today already have AES support built-in.

Rule one of cryptography: security by obscurity does not work.  If the system is not secure if your opponent knows how it works, it is not secure.  Rule two is that there is no point to making a system more secure than "practical cryptography," such as breaking and entering.  During WWII there were several naval engagements as part of practical cryptography to grab Naval Enigma machines and codebooks.