# Toy cipher — does it have a name?

When I was perhaps nine years, I borrowed a book from the library on various maths and CS topics. It outlined various simple ciphers, including one that I used a lot, just for fun. I can't remember the name of the book, or the name of the cipher, so I hope you can help me with the latter one.

It is a monoalphabetic substitution cipher with words as key. The key, an arbitrary word in the alphabet, is concatenated with the alphabet itself, and then duplicate letters are removed (keeping only the first occurrence). The resulting word is the cipher alphabet.

For instance, using the modern English alphabet and the key "STACKEXCHANGE", the cipher alphabet would become "STACKEXHNG" (key, later duplicates removed) concatenated with "BDFIJLMOPQRUVWYZ" (alphabet without letters from key):

plain  : ABCDEFGHIJ KLMNOPQRSTUVWXYZ
cipher : STACKEXHNG BDFIJLMOPQRUVWYZ


Of course, this cipher is insecure past the "highest" letter in the key (Y=Y, Z=Z), but it's still interesting as a practical explanation of substitution ciphers (perhaps even more, due to its weaknesses).

To repeat my question: does this scheme have a commonly known name? Or is known to be attributed to a person?

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This question seems better in crypto stack exchange. –  Terry Chia Jun 16 '12 at 14:37

## migrated from security.stackexchange.comJun 16 '12 at 18:18

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 Plaintext alphabet:    ABCDEFGHIJKLMNOPQRSTUVWXYZ