Substitution

The Porta cipher is a classical polyalphabetic substitution cipher invented by the Italian polymath Giambattista della Porta and published in his cryptographic work De Furtivis Literarum Notis in 1563. It belongs to the broader family of Renaissance-era ciphers that sought to overcome the weaknesses of monoalphabetic substitution by varying the encryption alphabet during the message.

The Keyed Caesar cipher is a variation of the classical Caesar cipher, adapted to increase security by combining a keyword with a shift-based substitution. The original Caesar cipher, attributed to Julius Caesar around 58–50 BCE, shifts each letter of the alphabet by a fixed number of positions. In the Keyed Caesar cipher, a keyword is first used to create a modified alphabet: the letters of the keyword are placed at the start of the alphabet (omitting duplicates), followed by the remaining unused letters in standard order.

The Kama-Sutra cipher, also known as the Kamasutra cipher, is a classical substitution cipher originating in ancient India and described in the Kama Sutra, traditionally attributed to Vātsyāyana around 300 CE to 400 CE. Despite its modern name association, the cipher itself is not related to sexuality; it appears in a section on secret writing as a practical method for discreet communication. The cipher is a simple monoalphabetic substitution system based on paired letters rather than a full substitution table.

The Baconian cipher is a substitution cipher devised by the English philosopher and statesman Francis Bacon in 1605. It represents one of the earliest examples of a binary-style encryption system, where each letter of the plaintext is encoded into a sequence of five symbols. Bacon originally used the letters A and B as the building blocks of his system, creating a simple yet ingenious method to conceal textual information within seemingly ordinary text.

The XOR Cipher is a symmetric key cipher that uses the logical XOR (exclusive or) operation for encryption and decryption. It gained prominence in computer science and cryptography for its simplicity and efficiency. The origins of the XOR Cipher are not attributed to a single creator or a specific date; rather, it has been known since the early days of binary computing, particularly during the 1960s.

The Vigenère cipher is a classical polyalphabetic substitution cipher developed in its modern form by the French cryptographer Blaise de Vigenère in 1586, although its conceptual origins trace back to Giovan Battista Bellaso in 1553. It encrypts text by shifting each letter of the plaintext according to the corresponding letter in a repeating keyword, effectively using multiple Caesar ciphers in sequence.

The Vernam cipher is a symmetric stream cipher invented by the American engineer Gilbert S. Vernam in 1917. It represents a foundational development in modern cryptography because it introduced the concept of combining plaintext with a random key using the bitwise XOR operation, which became the basis for the one-time pad. Vernam’s design originally targeted teleprinter communication systems, using a punched paper tape to supply the key stream.

The Trifid cipher is a classical fractionating cipher invented by the French cryptographer Félix Delastelle in 1901. It represents an important evolutionary step in cryptographic design because it deliberately combines substitution and transposition into a single coherent system. Delastelle developed the Trifid cipher as a more advanced successor to his earlier Bifid cipher, with the explicit goal of increasing diffusion by spreading the influence of each plaintext letter across multiple ciphertext characters.

The Templar Cipher is a cryptographic method associated with the Knights Templar, a medieval Christian military order founded during the Crusades. It is one of the many historical ciphers that have been attributed to the Knights Templar, although the exact cipher they used remains a subject of debate and speculation.

The Solitaire cipher, also known as the Pontifex cipher, is a manual encryption system invented by Bruce Schneier in 1999 to allow strong cryptography using a standard deck of playing cards. It functions as a stream cipher, producing a pseudo-random keystream from the deck that is then combined with plaintext letters modulo 26 to produce ciphertext. The cipher is fully reversible, so decryption uses the same keystream generated from an identically ordered deck.