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Another method consists of simple variations on the existing alphabet; uppercase, lowercase, upside down, etc. More artistically, though not necessarily more securely, some homophonic ciphers employed wholly invented alphabets of fanciful symbols. The book cipher is a type of homophonic cipher, one example being the Beale ciphers. This is a ...
The Copiale cipher is a substitution cipher. It is not a 1-for-1 substitution but rather a homophonic cipher: each ciphertext character stands for a particular plaintext character, but several ciphertext characters may encode the same plaintext character. For example, all the unaccented Roman characters encode a space.
Duke of Mantua Francesco I Gonzaga is the one who used the earliest example of homophonic Substitution cipher in early 1400s. [ 2 ] [ 3 ] Ibn al-Durayhim : gave detailed descriptions of eight cipher systems that discussed substitution ciphers, leading to the earliest suggestion of a "tableau" of the kind that two centuries later became known as ...
There are also historical music ciphers that utilize homophonic substitution (one-to-many), polyphonic substitution (many-to-one), compound cipher symbols, and/or cipher keys; all of which can make the enciphered message more difficult to break. [1]
A book cipher is a cipher in which each word or letter in the plaintext of a message is replaced by some code that locates it in another text, the key. A simple version of such a cipher would use a specific book as the key, and would replace each word of the plaintext by a number that gives the position where that word occurs in that book.
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 ]
The running key cipher is a polyalphabetic substitution, the book cipher is a homophonic substitution. Perhaps the distinction is most clearly made by the fact that a running cipher would work best of all with a book of random numbers, whereas such a book (containing no text) would be useless for a book cipher.
The earliest example of the homophonic substitution cipher is the one used by Duke of Mantua in the early 1400s. [24] Homophonic cipher replaces each letter with multiple symbols depending on the letter frequency. The cipher is ahead of the time because it combines monoalphabetic and polyalphabetic features.