No key is given. Detective days hand you the ciphertext and nothing else, so the work is finding the key — or proving which cipher it is — before you can read a word of it.
Free tool Have one to decode right now? Use the Affine Cipher toolIf the card says "key unknown" or names no method at all, it's a detective day. Look at what the text keeps: word lengths, letter frequencies, which characters appear.
Affine Each letter went through a·x + b, mod 26. There are only 312 keys — find two letters you're sure of and solve for a and b, or try them all.
TREASURE MAP
key unknown
UKXDPZKX LDA
No key was given, so the first job was finding one. Word lengths and letter patterns were the evidence. This one is Affine. The key: key unknown. Each letter went through a·x + b, mod 26. There are only 312 keys — find two letters you're sure of and solve for a and b, or try them all. Once the key is pinned down, the opening letters come back as T R E. The answer was TREASURE MAP.
Narrow it down before you decode. Count the letters, look for the one-letter words, and test the likeliest cipher first. Short words and common letters will give you the first foothold, and one correct letter usually leads to the next.
One a day, three guesses, and a streak that breaks the moment you miss one. Today’s is cipher #61.