So here's a little puzzle for all of the IT crowd out there.
It demonstrates the Vigenere cipher, the unexpectedly strong 'chiffre indéchiffrable'. The Wikipedia description explains how you can use the tabula recta to decode it.
Each row starts with a key letter. The remainder of the row holds the letters A to Z (in shifted order). Although there are 26 key rows shown, you will only use as many keys (different alphabets) as there are unique letters in the key string, here just 5 keys, {L, E, M, O, N}. For successive letters of the message, we are going to take successive letters of the key string, and encipher each message letter using its corresponding key row. Choose the next letter of the key, go along that row to find the column heading that matches the message character; the letter at the intersection of [key-row, msg-col] is the enciphered letter.
If you can't be bothered to do it by hand then there's a handy converter here at cryptii.com, which can handle a bunch of common ciphers.
Your ciphertext is:
WEMGO ZJLD EGH XJCD ELW
Let the countdown begin!
The solution is a short series of English dictionary words.
The key length is 9 characters.
OK, well evidently one of the things to watch for when setting this type of puzzle is that if you don't specify enough details of the plaintext or the key then the plaintext can be anything which fits the word boundaries. ;) Thank you Sp3000 for pointing this out in such an entertaining way.
