Symmetric

The Phillips Cipher is a classical polygraphic substitution cipher that encrypts plaintext by splitting it into fixed-size groups (typically digraphs or trigraphs) and then applying a series of transpositions and substitutions based on a keyword. It was designed to increase security over simple substitution ciphers by mixing the positions of letters within each group and leveraging the keyword to control letter mapping.

The Cadenus Cipher is a polyalphabetic substitution cipher that uses a repeating keyword to alter the shift of each plaintext character. Named in reference to classical ciphering techniques, it is similar in principle to the Vigenère Cipher, but often employs a direct letter-to-letter mapping that adapts dynamically according to the keyword.

The Progressive Caesar Cipher is an evolution of the classic Caesar Cipher, introducing a dynamic, position-based shift rather than a fixed one. In this system, each successive plaintext letter is shifted by an incrementally increasing value, starting from an initial shift. This creates a ciphertext that is harder to analyze with frequency techniques than the standard Caesar method.

The Variant Beaufort Cipher is a classical polyalphabetic substitution cipher closely related to the Vigenère Cipher and the original Beaufort Cipher. It uses a repeating keyword to transform plaintext letters, but differs in the way the substitution is calculated. Instead of adding or subtracting shifts directly, the Variant Beaufort Cipher uses a reversed tabula recta relationship, producing a distinct encryption pattern.

The XXTEA Cipher (Corrected Block Tiny Encryption Algorithm) is a further evolution of the TEA Cipher and XTEA Cipher, designed to fix structural weaknesses and improve block handling. Developed by David Wheeler and Roger Needham, XXTEA departs from the classic Feistel structure and instead operates on variable-length blocks, making it more flexible for real-world data.

The XTEA Cipher (eXtended Tiny Encryption Algorithm) is a symmetric block cipher designed as an improvement over the original TEA Cipher. Developed by David Wheeler and Roger Needham, XTEA was introduced to address weaknesses found in TEA, particularly its susceptibility to related-key attacks. While maintaining the same lightweight design philosophy, XTEA modifies the key schedule and round function to provide stronger security while remaining efficient and easy to implement.

The TEA Cipher (Tiny Encryption Algorithm) is a simple and efficient symmetric block cipher designed to be easy to implement while still providing a reasonable level of security. TEA operates on 64-bit blocks of data using a 128-bit key and applies a series of Feistel rounds involving bitwise operations, shifts, and additions. Its compact design makes it popular in constrained environments and educational contexts where understanding the mechanics of encryption is important.

The ChaCha20 Cipher is a modern symmetric stream cipher designed by Daniel J. Bernstein as an improvement over earlier stream ciphers like RC4. It operates by generating a secure pseudorandom keystream using a combination of a 256-bit key, a 96-bit nonce, and a counter. This keystream is then XORed with the plaintext to produce ciphertext. ChaCha20 is known for its speed, simplicity, and strong security properties, and is widely used in modern protocols such as TLS and VPN systems.

The RC4 Cipher (Rivest Cipher 4) is a symmetric stream cipher designed to encrypt data by generating a pseudorandom keystream that is combined with plaintext using bitwise XOR operations. Unlike block ciphers such as AES or DES, RC4 operates on data one byte at a time, making it fast and simple to implement. It was widely used in protocols like SSL/TLS and WEP, though it has since fallen out of favor due to discovered vulnerabilities.

The Rabbit Cipher is a high-speed stream cipher designed for efficient software implementation. Unlike block ciphers such as AES or DES, Rabbit generates a continuous keystream that is combined with plaintext using XOR operations to produce ciphertext. Originally developed in 2003 and later submitted to the eSTREAM project, Rabbit is known for its balance of performance and security, making it suitable for real-time encryption scenarios.