Autokey strikes again!

super_mega_worm_time_limited_free_game_4 (1)Did you know that the actual cipher invented by Blaise de Vigenère, back in the XVI century, is not the one that bears his name? The so-called Vigenère cipher was actually invented a few years earlier by Giovan Battista Bellaso. Vigenère’s own creation is a version of what today we call “autokey” cipher, and it is more secure than Bellaso’s. Of course, today’s computers can break both of them in seconds, but there things we can do to strengthen them to the current standard. Best of all, the resulting ciphers, which I’m calling “Visionnaire” and “Worm” (you will see why), can be done with paper and pencil. Visionnaire has its own article, so I’ll be talking about Worm here. (more…)

The Visionnarie cipher

Blaise-Vigenere.0 (1)The autokey cipher was invented nearly five hundred years ago by Blaise the Vigenère, pictured at left, but was almost immediately forgotten in favor of a much weaker repeating-key cipher invented by Bellaso, once upon a time known as “the undecipherable cipher,”  which Vigenère somehow got credit for. Given how many important secrets were revealed when that cipher was broken, the history of the world might have been quite different if Vigenére’s true creation had been the one people actually used. And this is the Visionnaire cipher: a simple combination of Vigenére’s autokey cipher with a substitution, made quite seamless to the user by means of a Tabula Recta. It turns out to be almost as strong as Worm, and much simpler to do. We can only speculate what might have been if this variation had been used back then. Nothing really prevented it. (more…)