Introduction to ciphers and substitution. Alice and Bob and Carl and Julius: terminology and Caesar Cipher ; The key to the matter: generalizing the Caesar Cipher ; Multiplicative ciphers ; Affine ...

Cryptography is nearly as old as human language. Many civilizations felt the need to conceal their messages using more or less sophisticated encryption methods, as demonstrated by some documentary ...

I hope you enjoyed Ed’s guest posts on NP-complete problems on TV the last couple of Mondays. It’s always great to hear from others on math that they are thinking about. This week it’s me again, and ...

It’s been a couple of Math Mondays since we last looked at columnar transposition ciphers, so let’s jump back in. In the It’s been a couple of Math Mondays since we last looked at columnar ...

Introduction If you need to send a secret message to a friend, how could you prevent other people from reading it? One way is to encrypt the message—that is, use a secret code that only you and your ...