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Modulo Cipher

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

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Modulo Cipher -

Tag(s) : Homophonic Substitution Cipher

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# Modulo Cipher

## Modulo N Encoder

### What is a Modulo cipher? (Definition)

A modulo cipher uses modular calculus on numbers in order to extract the remainder. The values obtained can then be used as a code/index for another cipher such as A1Z26 or the ASCII code.

### How to encrypt using Modulo cipher?

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)

### How to decrypt Modulo cipher?

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 A1Z26 (A=1, B=2, etc.)

### How to recognize Modulo ciphertext?

The ciphered message is constituted of somehow large random numbers.

### What are the variants of the Modulo cipher?

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

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Cite as source (bibliography):
Modulo Cipher on dCode.fr [online website], retrieved on 2023-02-08, https://www.dcode.fr/modulo-cipher

## Need Help ?

Please, check our dCode Discord community for help requests!
NB: for encrypted messages, test our automatic cipher identifier!