Obfuscation

The Three Square Cipher is a classical polygraphic substitution cipher that encrypts pairs of letters using three separate keyed squares. It is closely related to the Playfair Cipher and the Two-Square Cipher, but increases complexity by introducing a third square, which enhances diffusion and reduces recognizable patterns in the ciphertext.

The Digrafid Cipher is a classical digraphic substitution cipher that encrypts plaintext in pairs of letters, also known as digraphs. It uses a keyword to create a 5x5 (or 6x6 for extended alphabets) grid, similar in concept to the Playfair Cipher, but with modifications that enhance diffusion and obfuscation. Each digraph is mapped to another digraph according to the grid rules, producing ciphertext that appears less patterned than simple substitution ciphers.

The Gold-Bug Cipher is a substitution cipher made famous by Edgar Allan Poe in his short story The Gold-Bug. Unlike standard alphabetic ciphers, this system replaces letters with a mixture of symbols, numbers, and punctuation marks, creating a visually distinctive ciphertext. The cipher is monoalphabetic, meaning each plaintext letter always maps to the same symbol, but its unusual character set makes it appear more complex than it actually is.

The Myszkowski Transposition Cipher is a variation of the classical columnar transposition cipher that introduces a unique handling of repeated letters in the key. Named after its Polish origin, this cipher modifies the standard columnar approach by allowing duplicate key letters to share the same column rank, resulting in a more nuanced and less predictable rearrangement of the plaintext.

The Caesar Box Cipher is a classical transposition cipher that rearranges plaintext by placing it into a square or rectangular grid and then reading it out in a different order. Unlike the Caesar Cipher, which shifts letters within the alphabet, the Caesar Box Cipher preserves the original letters but alters their positions. This makes it a pure transposition cipher rather than a substitution cipher.

The Double Transposition Cipher is a classical manual cipher that applies two consecutive columnar transpositions to a plaintext message. Unlike a simple columnar transposition, which rearranges letters using a single key, the Double Transposition Cipher uses two separate keys sequentially, providing significantly stronger diffusion and making frequency analysis more difficult. Each key determines the column order for its respective transposition stage.

The Albam Cipher is a classical substitution cipher dating back to the early modern period. It is a simple monoalphabetic cipher in which each letter of the plaintext is replaced by the letter 13 positions ahead in a specialized rearranged alphabet. Unlike the standard Caesar Cipher, which shifts letters uniformly in the standard A–Z order, the Albam Cipher uses a fixed substitution mapping based on two halves of the alphabet: the first half (A–M) is paired with the second half (N–Z), and vice versa.

The XXTEA (Corrected Block Tiny Encryption Algorithm) is a further evolution of the TEA and XTEA, 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. This adjustment eliminates limitations found in TEA and XTEA, which both operate strictly on fixed 64-bit blocks.

The XTEA (eXtended Tiny Encryption Algorithm) is a symmetric block cipher designed as an improvement over the original TEA. 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 (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.