Symmetric

The DES Cipher (Data Encryption Standard) is a symmetric block cipher that encrypts data in 64-bit blocks using a 56-bit key. DES was developed in the 1970s and standardized by the U.S. National Bureau of Standards. It applies 16 rounds of a Feistel network with substitution and permutation steps to securely transform plaintext into ciphertext. While largely replaced by AES for modern security, DES remains an important example of classical symmetric encryption.

The AES Cipher (Advanced Encryption Standard) is a widely used symmetric block cipher designed to securely encrypt data. AES operates on 128-bit blocks using keys of 128, 192, or 256 bits and applies a series of substitution-permutation rounds to transform plaintext into ciphertext. It is a standard encryption algorithm in modern cryptography, replacing older systems like DES and 3DES due to its higher security and efficiency.

The 3DES Cipher (Triple Data Encryption Standard) is a symmetric block cipher that applies the DES algorithm three times to each block of data, significantly increasing security compared to single DES. It operates on fixed-size blocks and uses a key that is internally expanded to 24 bytes. In this implementation, the cipher supports multiple operation modes such as ECB, CBC, CFB, and OFB, along with configurable padding schemes and output formats.

The M-94 Cipher is a mechanical cipher system developed by the U.S. Army in 1922, using 25 rotating disks, each engraved with a scrambled alphabet. Messages are encoded by arranging the disks in a predetermined order and reading the ciphertext from a selected row. Each disk acts as a simple substitution cipher, but the combination of multiple disks creates a polyalphabetic substitution.

The Jefferson Disk Cipher, invented by Thomas Jefferson in the late 18th century, is a polyalphabetic substitution cipher that uses a set of rotating disks, each marked with a scrambled alphabet. Each disk represents a cipher alphabet, and by aligning the disks in a chosen sequence, the plaintext is encoded by selecting a row from the disks. This system effectively produces a complex, polyalphabetic cipher resistant to simple frequency analysis.

The Columnar Cipher is a classical transposition method that encrypts a message by rearranging entire columns of text according to a keyword. Unlike substitution systems such as the Caesar Cipher, the letters themselves are not altered — only their positions are changed.

It expands upon the simpler Columnar Cipher by explicitly reordering columns based on the alphabetical ranking of the keyword. This column permutation is the defining feature of the cipher.

The Cadenus–Gronsfeld Cipher is a variation of the Gronsfeld Cipher, itself a numeric version of the Caesar Cipher. It operates on alphabetic text by shifting each letter according to a repeating numeric key, but with the added twist that the key may include a reversible sequence or "cadenus" pattern, providing irregularity in the shifts. This makes it a hybrid between classical polyalphabetic ciphers and simple numeric substitution, increasing resistance to frequency analysis.

The Autokey Vigenère Cipher is an advanced polyalphabetic cipher that builds upon the classic Vigenère Cipher by incorporating an autokey mechanism. Instead of repeating a short keyword cyclically, the key is extended by appending the plaintext itself after the initial keyword. This produces a variable-length key, reducing repeating patterns in ciphertext and making frequency analysis considerably more difficult than in the standard Vigenère system.

The Trithemius Cipher is a polyalphabetic substitution cipher that shifts the alphabet progressively for each letter of the message. Instead of using a fixed shift like the Caesar Cipher, the shift increases step by step as the message is encoded.

The cipher was introduced by Johannes Trithemius in 1508. It works by applying a sequence of Caesar shifts to each letter of the plaintext. The first letter is shifted by 0, the second by 1, the third by 2, and so on. This changing shift produces a new substitution alphabet for every letter in the message.

The Porta Cipher is a classical polyalphabetic substitution cipher named after the Italian scholar Giambattista della Porta, who described it in the 16th century. It is a variant of the polyalphabetic cipher family, similar in principle to the Vigenère Cipher, but with a reciprocal structure that makes encoding and decoding symmetrical—using the same process in reverse produces the original text.