Cipher Identifier and Analyzer

Stuck with a cipher (cryptogram or other puzzle)? This tool will help you get started by analyzing your cipher and find the most likely encryption method used.

Cipher methods detected include:

  • Caesar cipher (including ROT13 and keyed Caesar ciphers)
  • Monoalphabetic substitution ciphers (including Atbash, Affine, etc)
  • Vigenère, Gronsfeld, Beaufort cipher
  • Columnar transposition ciphers, Railfence ciphers

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Analysis Summary

Your ciphertext is likely of this format:

The analysis indicates that the encoding used is likely one of the following:


      Caesar Cipher (including ROT13) Suggested

      The Caesar cipher, also known as a shift cipher, Caesar's code, or Caesar shift is one of the oldest and most famous ciphers in history. While being deceptively simple, it has been used historically for important secrets and is still popular among puzzlers.

      How It Works
      • Each letter of the alphabet is replaced by another letter from a shifted alphabet.
      • For example, with a right shift of 3, A becomes D, B becomes E, etc.
      • The ROT13 is a Caesar Cipher with a shift of 13.
      • The Keyed Caesar Cipher is a more difficult variant, where the starting letters of the alphabet is replaced by a secret keyword.

      Monoalphabetic Substitution Cipher Suggested

      The substitution cipher 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. Substitution ciphers are the most common examples of cryptograms (classical ciphers).

      How It Works
      • Each letter of the alphabet is replaced by another letter from another, secret, alphabet.
      • The American Cryptogram Association (ACA) uses the names Aristocrat (a cryptogram that includes separators between words) or Patristocrat (a cryptogram that doesn't separate words). In both cases, a letter is not allowed to be substituted by itself.
      • Instead of spaces, a letter like X can be used to separate words.
      • Affine cipher is a monoalphabetic substitution cipher where each letter is transformed using the function kx + m. It can be solved like any cryptogram.
      • Atbash cipher maps each letter to the opposite in the alphabet. For example A - Z, B - Y, C - X, etc.
      • Homophonic substitution ciphers use multiple, alternating, symbols for replacing plaintext letters. This makes frequency analysis much more difficult. An example of homophonic substitution cipher is the Beale cipher.

      Vigenère / Polyalphabetic Substitution Cipher Suggested

      Vigenère cipher is a polyalphabetic substitution cipher, named after the 16th century French diplomat Blaise de Vigenère but actually invented by Giovan Battista Bellaso. It was considered unbreakable for three centuries. Friedrich Kasiski is credited with publishing the first successful attack on this previously-unbreakable cipher in 1863.

      How It Works
      • The Vigenere cipher encrypts using a series of interwoven Caesar Ciphers, based on a keyword. For example if the keyword is ABC, it will encrypt by shifting the plaintext letters by 0, 1, 2, 0, 1, 2, 0, 1, 2, etc.
      • The shift can be described by a table. This table is usually called a tabula recta or a Vigenère table/Vigenère square.
      • Gronsfeld Cipher uses digits instead of letters in the key. It is similar to a Vigenère cipher that only uses letters A-J in the key.
      • Beaufort Cipher uses a reverse tabula recta, so that the cryptotext = key - plaintext.
      • The encryption process of Variant Beaufort Cipher is equivalent to the Vigenere cipher decryption process (and vice versa).

      Transposition Ciphers Suggested

      In a transposition ciphers, the plaintext message is scrambled by rearranging the letters. Transposition ciphers can be attacked by moving letters around and anagramming. They also can be attacked using brute-force methods if the key isn't long enough.

      How It Works
      • Letters are rearranged in a pattern. The pattern depends on the transposition cipher type and the secret keyword.
      • For example, in a columnar transposition cipher, the plaintext message is written out in rows and then read column by column. The keyword determines the order of the columns.
      • Columnar transposition cipher. In a columnar transposition cipher, the message is written in a grid of equal length rows, and then read out column by column. The columns are chosen in a scrambled order, decided by the encryption key.
      • Double-transposition cipher. This is equal to two columnar transposition ciphers.
      • Railfence cipher. In this cipher, the letters are written in a zig-zag pattern and then read row by row.