Tag Archives: secret codes

The Playfair Cipher

Code master Wheatstone

Among my second tier interests are murder mysteries, detective stories, and cryptography. The first typically includes the second, but there are many detective stories that don’t involve murder. Two of my favorite detectives, Spenser (by Robert B. Parker) and V.I. Warshawski (by Sara Paretsky), often have cases not involving murder.

The third interest I listed, cryptography, doesn’t usually coincide with the first two, but it did play a role in a recent locked-room murder mystery involving the delightful amateur detective Lord Peter Wimsey (by Dorothy L. Sayers). While I’ve always enjoyed secret codes, I’d never heard of the cipher Sayers used — the Playfair cipher.

It dates back to 1854, and is kind of cool, so I thought I’d share it.

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Secret Code

kid codeWhen I was a high school kid, my dad and I sometimes played a game where one of us would make up a secret code, write a message in that code, and the other would try to decipher the message. We generally used simple substitution ciphers, so it was an exercise in letter frequency analysis and word guessing.

There’s a cute secret code I found in a book back then that really stuck with me because of the neat way it looks. It also stuck with me because it’s so simple that once you learn it, you really can’t forget it.

So for some Saturday fun, I thought I’d share it with you.

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