Introduction to Trithemius and Keyword Ciphers

A few years ago I read Jason Fagone’s, The Woman Who Smashed Codes. It is a biography of Elizebeth Friedman, a woman who deciphered vital codes during prohibition and world wars. Her abilities rivaled those of William Friedman, her husband and the renowned “Father of Modern American Cryptology”.

Every day we pass information through all kinds of means – smiles, conversations, emails, YouTube videos – much of this information is visible to all, but only understood by a few. For instance, a pet phrase you say when angry would alert friends of your emotional state, but without any other clues the broader population might remain clueless.

Plain-sight codes seem ridiculous, don’t they? Inconspicuously dressed spies handing off notes in back alleys makes sense, but with the rise of radio, powers began to broadcast their messages in such a way that anyone could listen in. It feels like the equivalent of a spy flapping their arms, screaming “I have a secret!” and then speaking a different language. That sure gets everyone’s attention, but as long as no enemies speak the second language, the information is safe.

There are so many methods of encryption, but to whet your appetite, I have made two videos showing how to write a short program for two kinds of ciphers in particular; the Trithemius cipher, which I always manage to mispronounce, and the keyword cipher.

Using a computer to encode a message is so delightfully mischievous, I truly hope you find the time to try out the code from the videos yourself!

References:

[1] FAGONE, J. (2018). Woman who smashed codes. DEY STREET Books, HARPER.