Symmetric

The M-94 Cipher is a mechanical polyalphabetic cipher device used by the United States military, based on the earlier Jefferson Disk cipher invented by Thomas Jefferson in 1795. It was officially adopted in the early 20th century, around 1922, to provide secure field communication before the widespread use of electronic encryption machines. The device consists of a set of rotating disks mounted on a cylinder, each disk engraved with a scrambled alphabet.

The Jefferson Disk cipher, also known as the Wheel Cipher, is a classical mechanical cipher invented by the American statesman Thomas Jefferson around 1795. It consists of a set of rotating disks, each engraved with the letters of the alphabet in a scrambled order, mounted on a spindle. By arranging the disks in a particular sequence determined by a key, a plaintext message can be encoded into a seemingly random string of letters. Decryption requires the recipient to have an identical set of disks arranged in the same order.

The Morse Code is a method of encoding textual information using sequences of short and long signals—commonly called “dots” and “dashes”—invented by the American artist and inventor Samuel F. B. Morse and his collaborator Alfred Vail in 1837. Originally developed for telegraph communication, Morse Code translates letters, numbers, and punctuation into variable-length sequences of electrical pulses, audible tones, or visual signals, allowing messages to be sent across long distances using a binary-like system.

The Columnar Transposition cipher is a classical transposition cipher widely used in the 16th and 17th centuries, though its origins are often attributed to various European cryptographers experimenting with letter rearrangement methods. Unlike substitution ciphers, the Columnar Transposition cipher does not alter the letters themselves but instead rearranges their order according to a predetermined key. The cipher’s security relies on the secrecy of the key, which determines the column order used to read off the message after writing it in rows.

The Cadenus–Gronsfeld cipher is a hybrid classical cipher that combines the key-based numeric shifts of the Gronsfeld cipher, a variant of the Vigenère cipher popularized in the 19th century, with an autokey-like sequence inspired by Cadenus, an early cryptographic system emphasizing dynamic key extension. While the exact origins of the Cadenus–Gronsfeld cipher are less documented, it emerged as a method to improve the security weaknesses of simple repeating-key polyalphabetic ciphers.

The Autokey Vigenère cipher is an extension of the classical Vigenère cipher, designed to eliminate the repeating key weakness and increase security. It was popularized by the British cryptographer Giovanni Battista Bellaso in 1553 and later refined in practice by various cryptographers, though its autokey variant became well known in the 19th century.

The Trithemius cipher is a polyalphabetic substitution cipher invented by the German abbot and cryptographer Johannes Trithemius in 1508. It is considered one of the earliest examples of systematic polyalphabetic encryption, preceding the more widely known Vigenère cipher by several decades. The key innovation of the Trithemius cipher is that it uses a progressive shift based on the position of each letter in the plaintext rather than a repeating keyword.

The Porta cipher is a classical polyalphabetic substitution cipher invented by the Italian polymath Giambattista della Porta and published in his cryptographic work De Furtivis Literarum Notis in 1563. It belongs to the broader family of Renaissance-era ciphers that sought to overcome the weaknesses of monoalphabetic substitution by varying the encryption alphabet during the message.

The M-209 cipher is a mechanical rotor-based cipher device developed by the American engineer Boris Hagelin and adopted by the U.S. military in 1941. It was a portable, hand-operated machine designed for tactical battlefield communications, encrypting messages character by character using a combination of rotors, a rotating drum with movable pins, and a set of lugs to generate a polyalphabetic substitution.

The Lorenz cipher was a high-level German cipher machine used during World War II, developed by the Lorenz company around 1940. It was designed to encrypt teleprinter communications for the German Army, producing ciphertext in the Baudot code format. Unlike the simpler Enigma machine, the Lorenz cipher used twelve wheels with a complex system of rotations to generate a pseudo-random key stream, creating a stream cipher that combined plaintext bits with key bits via modulo-2 addition (XOR).