Transposition cipher

Plaintexts can be rearranged into a ciphertext using a key, scrambling the order of characters like the shuffled pieces of a jigsaw puzzle.

Transposition ciphers have several vulnerabilities (see the section on "Detection and cryptanalysis" below), and small mistakes in the encipherment process can render the entire ciphertext meaningless.

For example, using three "rails" and a message of 'WE ARE DISCOVERED FLEE AT ONCE', the encrypter writes out: Then reads off: (The cipher has broken this ciphertext up into blocks of five to help avoid errors.

In fact, for messages of reasonable length, the number of possible keys is potentially too great to be enumerated even by modern machinery.

[citation needed] In the middle of the 17th century, Samuel Morland introduced an early form of columnar transposition.

In a regular columnar transposition, we write this into the grid as follows: providing five nulls (QKJEU), these letters can be randomly selected as they just fill out the incomplete columns and are not part of the message.

In the following example, we use the keys JANEAUSTEN and AEROPLANES to encrypt the following plaintext: "Transposition ciphers scramble letters like puzzle pieces to create an indecipherable arrangement.

As an example, we can take the result of the irregular columnar transposition in the previous section, and perform a second encryption with a different keyword, STRIPE, which gives the permutation "564231": As before, this is read off columnwise to give the ciphertext: If multiple messages of exactly the same length are encrypted using the same keys, they can be anagrammed simultaneously.

During World War I, the German military used a double columnar transposition cipher, changing the keys infrequently.

The system was regularly solved by the French, naming it Übchi, who were typically able to quickly find the keys once they'd intercepted a number of messages of the same length, which generally took only a few days.

[3] During World War II, the double transposition cipher was used by Dutch Resistance groups, the French Maquis and the British Special Operations Executive (SOE), which was in charge of managing underground activities in Europe.

[7] A variant form of columnar transposition, proposed by Émile Victor Théodore Myszkowski in 1902, requires a keyword with recurrent letters.

Plaintext columns with unique numbers are transcribed downward; those with recurring numbers are transcribed left to right: A disrupted transposition cipher[8] further complicates the transposition pattern with irregular filling of the rows of the matrix, i.e. with some spaces intentionally left blank (or blackened out like in the Rasterschlüssel 44), or filled later with either another part of the plaintext or random letters.

The resulting ciphertext (the columns read according to the transposition key) is "WCEEO ERET RIVFC EODN SELE ADA".

This can produce a highly irregular transposition over the period specified by the size of the grille, but requires the correspondents to keep a physical key secret.

These include: The third method was developed in 1878 by mathematician Edward S. Holden and New-York Tribune journalists John R. G. Hassard and William M. Grosvenor who managed to deciphere telegrams between the Democratic Party and their operatives in the Southern states during the 1876 presidential election and thus prove facts of vote buying, influencing the 1878-1879 congressional elections.

[14] A detailed description of the cryptanalysis of a German transposition cipher can be found in chapter 7 of Herbert Yardley's "The American Black Chamber."

A cipher used by the Zodiac Killer, called "Z-340", organized into triangular sections with substitution of 63 different symbols for the letters and diagonal "knight move" transposition, remained unsolved for over 51 years, until an international team of private citizens cracked it on December 5, 2020, using specialized software.

For example, the plaintext alphabet could be written out in a grid, and every letter in the message replaced by its co-ordinates (see Polybius square and Straddling checkerboard).

[16] Another method of fractionation is to simply convert the message to Morse code, with a symbol for spaces as well as dots and dashes.

Looping the scrambling process on the binary string multiple times before changing it into ASCII characters would likely make it harder to break.