ASCII Modulated Vigenere Cryptography  

Summary
Shortened in title to “AMV “ cryptography this cryptography is on debut here as a
class of cryptography rather than a one-off cipher type. It is a modern, stylised
version of the cryptography invented by Blaise Vigenere in about 1580. The
cryptography is computer intensive almost to the extent that it would be too difficult
to use by longhand methods and must be computer driven. The ASCII set of
characters has enormous presence in this cryptography in that it is an enumeration
data type that is at the heart of most modern programming languages and digital
computers. It is a powerful adjunct to Vigenere’s cipher that emerges from the past as
a timely proposition 400 years after his death. ASCII is used here to create several
distinct alphabets within the same algorithm that provide the all-important
randomness that is required for an unbreakable one-time pad type cipher. This
cryptography is independent of computer power for all time and will work in any
computer no matter how old. The ciphers are written in the Ada-95 programming
language.

Security
Should Eve intercept the cipher text, she has no means whatever of deciphering the
ciphertext by linguistic probability means as Babbage and Kasiski did in the distant
past. That is due to using the entire 95 writable characters (of the first 128) of ASCII
latin-1 as the Vigenere square which is at the heart of the Vigenere cipher. Blaise
Vigenere (1580) used only the 26 letters of the English language as his square
alphabet.

If a message is 10000 characters of ciphertext long then there are 10000 factorial, in
number, possible strings of characters in the message ‘space’ of candidate strings and
any one of them could be the right one. Eve can do no more that guess at which one is
the right one. The ciphertext sequence to hand by Eve is itself intrinsically safe
because of being innately random i.e., a sequence that has no pattern and has equal
probability over its entire length.

The public key of the message, i.e., the ciphertext string, is the same length as the
message it represents and the encryption key, also equal in length to the message
length, is used once and only once before being changed for a fresh key.

The claim being made here is that subject to beta testing, the prototype cipher that is
already in existence, i.e.,up and running, is theoretically unbreakable.

Encryption / decryption rate on a 1 gigabyte processor and 384 megabytes of RAM is
roughly 3000 characters per second. Ciphertext expansion = zero ( => 1 to 1).

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