affine.md

Multiplicative cipher

The multiplicative cipher is an easy substitution cipher. All letters will converted to number and then multiplied by the set key and converted back to letters.

Cipher behavior information

• Case sensitive? ✓
• Deterministic? ✓
• Alphabet: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
• Characters not in alphabet will be: omitted, preserved (default), throw an error

Default options object

const options = {
  key: 3, // The number the letters should be multiplied with
  failOnUnknownCharacter: false, // Should an error be thrown on unknown characters
  omitUnknownCharacter: false   // Should unknown characters be omitted
}

ATTENTION: Only the keys 3, 5, 7, 9, 11, 15, 17, 19, 21, 23 and 25 are legal, because they are co-prime to 26.

Usage

Encoding

Default

import { multiplicative } from 'cipher-collection'


console.log(multiplicative.encode('ABCD')) // ADGJ
console.log(multiplicative.encode('ABCD01/')) // ADGJ01/

Omit unknown character

import { multiplicative } from 'cipher-collection'


console.log(multiplicative.encode('ABCD01/'), { omitUnknownCharacter: true } ) // ADGJ

Fail on unknown character

import { multiplicative } from 'cipher-collection'


console.log(multiplicative.encode('ABCD01/'), { failOnUnknownCharacter: true } ) // Error will be thrown

With different key

import { multiplicative } from 'cipher-collection'


console.log(multiplicative.encode('ABCD', { key: 25 } )) // AZYX

Decoding

Default

import { code } from 'cipher-collection'


console.log(code.decode('ciphertext')) // Cleartext

Omit unknown character

import { multiplicative } from 'cipher-collection'


console.log(multiplicative.encode('ADGJ01/'), { omitUnknownCharacter: true } ) // ABCD

Fail on unknown character

import { multiplicative } from 'cipher-collection'


console.log(multiplicative.encode('ADGJ01/'), { failOnUnknownCharacter: true } ) // Error will be thrown

With different key

import { multiplicative } from 'cipher-collection'


console.log(multiplicative.encode('AZYX', { key: 25 } )) // ABCD