The message is called the plaintext because it is the unchanged source information. Example: The cat ran away. The secret message generated is called a cipher or ciphertext and it is the encrypted ...

You can make a message secret in countless different ways. One common way is to use a substitution cipher, in which one letter is substituted for another. Another is to employ a transposition cipher, ...

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 ...