Matrix

The Wheatstone cipher is a classical cipher system developed by the English scientist Charles Wheatstone in 1854. It is a type of polyalphabetic transposition cipher, often implemented using a mechanical device called the Playfair cipher square, which Wheatstone popularized and patented. The system was designed to encrypt pairs of letters rather than individual letters, introducing a degree of diffusion that makes simple frequency analysis much less effective.

The Trifid cipher is a classical fractionating cipher invented by the French cryptographer Félix Delastelle in 1901. It represents an important evolutionary step in cryptographic design because it deliberately combines substitution and transposition into a single coherent system. Delastelle developed the Trifid cipher as a more advanced successor to his earlier Bifid cipher, with the explicit goal of increasing diffusion by spreading the influence of each plaintext letter across multiple ciphertext characters.

The Polybius Square cipher is a classical substitution cipher invented by the ancient Greek historian and scholar Polybius around 200 BCE. It converts letters into pairs of numbers based on a 5×5 square grid, allowing plaintext to be transmitted using numbers instead of letters. Traditionally, the letters I and J are combined to fit the 25-cell grid.

The Playfair Cipher is a manual symmetric encryption technique that encrypts pairs of letters (bigrams) instead of single letters. It was invented by Charles Wheatstone in 1854 but became known as the Playfair Cipher after it was promoted by Lord Playfair. This cipher was used extensively during the World War I era for secure military communications, as it provided better security than simple substitution ciphers by addressing frequency analysis vulnerabilities.

The Hill cipher is a polygraphic substitution cipher invented by the American mathematician Lester S. Hill in 1929. Unlike simple substitution ciphers, the Hill cipher encrypts blocks of letters using linear algebra, making it one of the first ciphers to apply matrix operations to cryptography. Each block of plaintext letters is represented as a vector of numbers (with A=0, B=1, …, Z=25) and multiplied by an invertible key matrix modulo 26.

The Grid Transposition Cipher is a method of encryption that involves rearranging the characters of a message based on a predetermined grid pattern. It is a type of transposition cipher, where the original letters of the plaintext are maintained, but their positions are altered to create the ciphertext.

The Foursquare cipher is a polygraphic substitution cipher developed by F. A. Wheatstone in 1890. In this three-key variation, four 5×5 matrices are used: the top-left matrix is filled with the letters of Key 1 followed by the remaining alphabet, the top-right matrix uses Key 2, the bottom-left matrix uses Key 3, and the bottom-right matrix contains the standard alphabet in order. Encryption works on digraphs (two-letter pairs) of plaintext.

The Columnar cipher, also called the Columnar transposition cipher, is a classical cipher method used since at least the 16th century. Instead of substituting letters, it encrypts messages by rearranging their positions according to a key. The key is usually a word, and its letters determine the columns in which the plaintext is written row by row. Encryption then reads the columns in the order the key letters appear in the original key, rather than alphabetically, which affects the final ciphertext.

The Bifid Cipher is a Fractionating Transposition cryptographic technique that was invented by the French amateur cryptographer Félix Delastelle in 1901. It is a fractionating transposition cipher that combines elements of both substitution and transposition methods.

The Bifid Cipher operates on a square grid known as the Polybius square or Polybius checkerboard. This square consists of a 5x5 grid containing the letters of the alphabet (usually excluding the letter J).