The cryptogram is one of the oldest classical ciphers. It is simple enough that it usually can be solved by hand. Each letter is replaced by a different letter of the alphabet, so solving the puzzle means finding out the original lettering. A cryptogram is also called a monoalphabetic substitution cipher.
- The cryptogram is a monoalphabetic substitution cipher.
- The American Cryptogram Association (ACA) uses the names Aristocrat (a cryptogram that includes separators between words) or Patristocrats (a cryptogram that doesn't separate words). In both cases, a letter is not allowed to be substituted by itself.
- Cryptograms originally were intended for military or personal secrets. The first know usage for entertainment purposes occured during the Middle Ages.
- Instead of spaces, a letter like X can be used to separate words.
- Frequency analysis can be used to find the most commonly used letters.
- There is also a variant of the Caesar Cipher called Keyed Caesar Cipher, which uses a secret code word to decide the order of the first letters in the translation alphabet.
Cryptograms, and variants of it, are very frequently used in geocaching mystery caches, and easy logic puzzles. It can be detected using letter frequency analysis of the ciphertext.
See also: Code-Breaking overview | Adfgvx cipher | Adfgx cipher | Atbash cipher | Beaufort cipher | Bifid cipher | Caesar cipher | Columnar transposition | Double transposition | Enigma machine | Four-square cipher | Gronsfeld cipher | Keyed caesar cipher | One-time pad | Pigpen cipher | Playfair cipher | Rail fence cipher | Rot13 | Trifid cipher | Variant beaufort cipher | Vigenère cipher