Tool to decrypt/encrypt with modulo. Modulo calculations applied on numbers can make possible ciphering using the calculated values.

Modulo Cipher - dCode

Tag(s) : Homophonic Substitution Cipher

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**Modulo Cipher** Encryption uses modular arithmetics and a sequence of numbers, characters must be converted into numbers, e.g. A=1, B=2, ... Z=26, but any numeric conversion (like the ASCII table) is fine.

__Example:__ To crypt DCODE with the modulo 26, convert the text to numbers 4,3,15,4,5.

For each number to encrypt, calculate a random number which value is equal to the number to crypt.

__Example:__ For $ 4 $, take $ 654 $, as $ 654 \equiv 4 \ mod 26 $

For $ 3 $, take $ 965 $, as $ 965 \equiv 3 \ mod 26 $.

The encrypted message is 654,965,561,732,941 (many other cipher message are possible)

Decryption requires to know the value of the Modulo and to know the series of number to decrypt.

__Example:__ The encrypted message is 654,965,561,732,941with the modulo 26.

For each number N, calculate the value of the remainder in the euclidean division of N by the modulo to get the plain number.

__Example:__ The plain text is 4,3,15,4,5, that can be translate into DCODE with A=1, B=2, ...

The ciphered message is constituted of somehow large random numbers.

The Affine cipher use modulo in the calculation $ C = a \times P + b \ mod 26 $

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NB: for encrypted messages, test our automatic cipher identifier!

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Source : https://www.dcode.fr/modulo-cipher

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