Symmetric

The Solitaire Cipher, also called the Pontifex Cipher, is a manual encryption system created by Bruce Schneier to allow secure message encryption using a deck of playing cards. Each card represents a number, and the deck is manipulated in a series of steps (joker moves, triple cuts, and count cuts) to generate a pseudorandom keystream. Letters of the plaintext are then converted to numbers (A=1, B=2, …, Z=26) and combined with the keystream numbers modulo 26 to produce ciphertext.

The Simple Substitution Cipher is a classical monoalphabetic substitution cipher where each letter in the plaintext is replaced by a corresponding letter from a fixed, pre-agreed cipher alphabet. Unlike the Caesar Cipher, which shifts letters by a fixed number, the Simple Substitution Cipher allows a completely arbitrary mapping of the 26 letters, providing more variability and slightly stronger security against casual frequency analysis.

The Scytale Cipher is an ancient transposition cipher used by the Spartans. A message is written along the length of a cylinder (or strip of parchment wrapped around a rod), and the ciphertext is read by unwrapping the strip and reading column by column. This method rearranges the letters of the plaintext while preserving all characters, providing basic encryption.

The Running Key Cipher is a polyalphabetic substitution cipher that uses a long piece of text as the key instead of a short repeating keyword. The key must be at least as long as the plaintext. Each letter of the plaintext is combined with the corresponding letter of the key using modular arithmetic based on the alphabet.

The Rout Cipher is a columnar transposition cipher that rearranges letters of a plaintext into a grid defined by a keyword. Letters are then read off column by column in alphabetical order of the keyword letters. Spaces are removed during encoding, and if the last row is incomplete, it may be padded to fill the grid. The recipient decodes by reconstructing the grid and reading row by row.

Its security relies entirely on the secrecy of the keyword. It does not substitute letters but only rearranges them.

The ROT Cipher is a simple monoalphabetic substitution cipher that shifts each letter of the plaintext by a fixed number of positions in the alphabet. “ROT” stands for “rotate,” and the most common variant is ROT13, which shifts letters by 13 positions. This means that A becomes N, B becomes O, and so on, wrapping around the alphabet. Because the English alphabet has 26 letters, applying ROT13 twice restores the original text.

The Rosicrucian Cipher is a historical substitution cipher associated with the secretive Rosicrucian order, a mystical and philosophical society that emerged in early 17th-century Europe. It was primarily used to encode the order's esoteric texts, manifestos, and personal communications. The cipher disguises letters through a systematic symbolic substitution known only to initiates, allowing messages to remain hidden in plain sight.

The Rail Fence Cipher is a classical transposition cipher that rearranges the letters of a plaintext message into a zigzag pattern across multiple "rails" (rows) and then reads them sequentially row by row to form the ciphertext. It is a simple but effective method for obscuring the order of letters, making it harder for casual observers to read the message without knowing the number of rails used.

The Polygraphia Cipher originates from the work Polygraphia, a 16th-century cryptographic treatise written by the German abbot and polymath Johannes Trithemius and first published in 1518. The book is considered the first printed work devoted entirely to cryptography. Among its many systems, Trithemius introduced a progressive substitution method in which the encryption alphabet changes with each letter of the message.

The Polybius Cipher, also known as the Polybius Square, is a classical substitution cipher invented by the ancient Greek historian and scholar Polybius. It encodes letters as pairs of numbers corresponding to their position in a 5×5 grid, allowing letters to be represented numerically. To fit the 26-letter Latin alphabet into a 25-cell square, the letters I and J are typically combined.