Shuffled Letters

Letter shuffling involves changing the order of the characters in a message. Mathematically, it means permuting the positions of the letters.

In cryptography, this process corresponds to a transposition cipher: the letters remain the same, only their order changes. For the operation to be reversible, the shuffling must meet certain criteria.

Several methods are possible:

Mix by writing backwards

An easy reversible mixing is to write backward, the message become less readable.

Start-end cycle shuffle

The first letter goes at the beginning, the next at the end, then at the beginning and so on

Mix by random write

Split by words

In order not to make too complex mixtures, the message can be broken down into words. It will then generate an anagram of the word (which exists or not).

Split by blocks

For an easier shuffling, the message may be broken down by a fixed block size. Generally, it is best to use short blocks.

Transposition

dCode offers a tool for performing transposition ciphers.

Deciphering involves finding the inverse permutation applied during the shuffling.

If permutation P was used, simply applying its inverse permutation P-1 restores the original order.

— Case of a single word: find all possible anagrams. A word of N letters has a maximum of N! (factorial of N) permutations.

— Case of a fixed-size block: Test the possible permutations of the block.

— Case of a complete sentence without a key: Exhaustively exploring this space is unrealistic without structural clues (language, letter frequencies, syntactic constraints).

Thus, keyless deciphering relies on statistical, linguistic, or heuristic methods, but quickly becomes impractical as the length increases.

dCode has a tool for mixing the letters of a message while keeping it (theoretically) readable by a human: see the typoglycemia tool.