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A monoalphabetic cipher uses fixed substitution over the entire message, whereas a polyalphabetic cipher uses a number of substitutions at different positions in the message, where a unit from the plaintext is mapped to one of several possibilities in the ciphertext and vice versa.
The Aristocrat Cipher is a type of monoalphabetic substitution cipher in which plaintext is replaced with ciphertext and encoded into assorted letters, numbers, and symbols based on a keyword. The formatting of these ciphers generally includes a title, letter frequency, keyword indicators, and the encoder's nom de plume . [ 1 ]
Homophonic substitution: Use of homophones — several alternatives to the most common letters in otherwise monoalphabetic substitution ciphers. For example, for English, both X and Y ciphertext might mean plaintext E. Polyalphabetic substitution, that is, the use of several alphabets — chosen in assorted, more or less devious, ways (Leone ...
The affine cipher is a type of monoalphabetic substitution cipher, where each letter in an alphabet is mapped to its numeric equivalent, encrypted using a simple mathematical function, and converted back to a letter. The formula used means that each letter encrypts to one other letter, and back again, meaning the cipher is essentially a ...
The previous examples were all examples of monoalphabetic substitution ciphers, where just one cipher alphabet is used. It is also possible to have a polyalphabetic substitution cipher, where multiple cipher alphabets are used. The encoder would make up two or more cipher alphabets using whatever techniques they choose, and then encode their ...
Sometimes values are reported without the normalizing denominator, for example 0.067 = 1.73/26 for English; such values may be called κ p ("kappa-plaintext") rather than IC, with κ r ("kappa-random") used to denote the denominator 1/c (which is the expected coincidence rate for a uniform distribution of the same alphabet, 0.0385=1/26 for ...
600-500 – Hebrew scholars make use of simple monoalphabetic substitution ciphers (such as the Atbash cipher) c. 400 – Spartan use of scytale (alleged) c. 400 – Herodotus reports use of steganography in reports to Greece from Persia (tattoo on shaved head) 100-1 A.D.- Notable Roman ciphers such as the Caesar cipher.
The Atbash cipher is a particular type of monoalphabetic cipher formed by taking the alphabet (or abjad, syllabary, etc.) and mapping it to its reverse, so that the first letter becomes the last letter, the second letter becomes the second to last letter, and so on. For example, the Hebrew alphabet would work like this: