Cutting edge stuff for Machiavelli (encryption humor)

Back in the 1500s there was a celebrated political scientist was hard at work writind a book. It was The Prince and the author was Machiavelli. His work was at a time when crytography was on the brink of a breakthrough. The Vigenere Cipher was invented soon thereafter. It was unbreakable for a limited time, but set a historic precedent for ciphers bringing security not available in other ways. Nowadays, its limited unicity distance is now its primary failing, with some things not usually noted about the cipher. A backwards ("wrong") lookup of the vigenere cipher makes a servicable hash. This is weak by being the same length as the password, but nonetheless is not reversible as far as I can tell. As for a short unicity distance? A double encryption with Vigenere is not a group, and distributes the entropy over a unicity distance equal to the lowest common product of the prime factors of successive keywords. For example: A five letter password and a six letter password would make a 5*3*2=30 block unicity distance. A five letter password and an eleven letter password would give you 55 secure letters of encryption. To break Vigenere, you line up the message in columns (55 columns in this example,) and treat each column as an individual substitution cipher. Statistically, this is impractical to break in less than 30 rows (think t-testing) and actually only becomes "easy" at around 120 rows. 55 Characters * 120 rows = 600 characters of reasonable privacy. Properly implemented, using a Diffie-Hellman Key Exchange it would make an excellent way to offer secure Cell Phone Text messaging, even today.