We all have secrets to keep. Those secrets could be personal dirt we want to keep from others, or they could be something as mundane as our credit card numbers or medical histories. But all of us have ...

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 ...

Here's your chance to crack ciphers similar to those Bletchley Park's codebreakers faced during World War II. Below, we present three ciphers of different levels of difficulty, from easiest to most ...

The keys are correct as stated, but instead of numbering duplicate letters from left to right, Agent Madeleine numbered them from right to left. You may want to complete the decryption yourself before ...

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 ...