Substitution

The Vatsyayana Cipher is a classical monoalphabetic substitution cipher that uses a keyword to generate a fixed substitution alphabet. It is structurally similar to other keyword-based substitution systems, but often emphasizes preserved spacing and case sensitivity, making it suitable for mixed-format plaintext input.

The cipher derives its name from historical cryptographic naming conventions associated with early substitution systems, and operates by constructing a deterministic mapping between plaintext and ciphertext letters using a keyword-generated alphabet.

The Ragbaby Cipher is a monoalphabetic substitution cipher that uses a keyword to scramble the alphabet while preserving the case of letters. It preserves spaces and faithfully encodes/decode letters according to the keyword mapping.

Ragbaby Cipher: Encoding

To encode using the Ragbaby Cipher with a keyword:

The Patristocrat Cipher is a classic monoalphabetic substitution cipher where all spaces, punctuation, and formatting are removed before encryption. This produces a continuous string of letters, making frequency analysis slightly more challenging.

Patristocrat Cipher: Encoding

To encode with the Patristocrat Cipher using a keyword:

The Acrostic Cipher is a form of substitution cipher that encodes plaintext by mapping it into words or blocks such that certain letters (usually the first letters of each block) form the original message when read sequentially. It combines simple substitution with structured presentation, often used for secret messages hidden in poems, lists, or block-formatted text.

In this implementation, the plaintext is split into blocks of fixed size for readability, and a key is used to determine the substitution pattern for letters.

The Chaotic Substitution Cipher is a variation of the classical substitution cipher that introduces dynamic, position-dependent transformations to produce less predictable ciphertext. Unlike a standard Monoalphabetic Substitution Cipher, where each letter maps consistently to a single counterpart, the Chaotic Substitution Cipher alters its mapping behavior based on position, keyword influence, or internal shifting rules.

The Nomenclator Cipher is a classical encryption system that combines a substitution cipher with a codebook. Unlike standard substitution ciphers that operate purely on individual letters, the Nomenclator Cipher allows entire words, names, or phrases to be replaced with predefined numeric or symbolic codes. This hybrid approach significantly enhances security by masking both letter frequencies and common word patterns.

The Monoalphabetic Substitution Cipher is one of the simplest and most fundamental encryption techniques. It works by replacing each letter in the plaintext with a corresponding letter from a fixed substitution alphabet. Unlike polyalphabetic ciphers, the mapping remains constant throughout the entire message, meaning each plaintext letter always maps to the same ciphertext letter.

The Progressive Key Cipher is a variation of the classical polyalphabetic substitution cipher that extends the Vigenère Cipher by introducing a progressive shift to the key itself. Instead of repeating the keyword unchanged, each repetition of the key is incrementally shifted, causing the encryption pattern to evolve as the message progresses.

The Bellaso Cipher is a classical polyalphabetic substitution cipher invented by Giovanni Battista Bellaso in the 16th century. It extends the principles of the earlier Caesar Cipher by using a repeating keyword to vary the shift for each letter, effectively creating a polyalphabetic encryption system. Each letter in the plaintext is shifted by the value of the corresponding letter in the keyword, repeated as necessary to match the plaintext length.

The Checkerboard Cipher, also known as the Polybius Checkerboard Cipher, is a classical substitution cipher that converts letters into numeric pairs or digits using a keyword-based grid. Each letter is assigned a coordinate in a 5x5 or 6x5 checkerboard matrix, with the keyword determining the arrangement of letters. This approach allows letters to be represented as one or two digits, providing a compact numeric encoding while introducing a keyed substitution system.