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Adds Affine/Atbash Cipher encryption/decryption

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- 3 new operations - Affine Encode, Decode and Atbash Cipher
- Added 3 new utils - mod, GCD and modInv
This commit is contained in:
Matt C 2017-02-08 11:51:37 +00:00
parent 35d74980a1
commit 2750be36da
8 changed files with 247 additions and 83 deletions
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84
src/js/operations/Cipher.js
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@ -385,7 +385,6 @@ var Cipher = {
return encrypted.ciphertext.toString(Utils.format[args[2]]);
},
/**
* Vigenère Encode operation.
*
@ -475,6 +474,89 @@ var Cipher = {
return output;
},
/**
* @constant
* @default
*/
AFFINE_A: 1,
/**
* @constant
* @default
*/
AFFINE_B: 0,
/**
* Affine Cipher Encode operation.
*
* @author Matt C [matt@artemisbot.pw]
* @param {string} input
* @param {Object[]} args
* @returns {string}
*/
runAffineEnc: function (input, args) {
var alphabet = "abcdefghijklmnopqrstuvwxyz",
a = args[0],
b = args[1],
output = "";
if (!/^\+?(0|[1-9]\d*)$/.test(a) || !/^\+?(0|[1-9]\d*)$/.test(b)) return "The values of a and b can only be integers.";
for (var i = 0; i < input.length; i++) {
if (alphabet.indexOf(input[i]) >= 0) {
// Uses the affine function ax+b % m = y (where m is length of the alphabet)
output += alphabet[((a * alphabet.indexOf(input[i])) + b) % 26];
} else if (alphabet.indexOf(input[i].toLowerCase()) >= 0) {
// Same as above, accounting for uppercase
output += alphabet[((a * alphabet.indexOf(input[i].toLowerCase())) + b) % 26].toUpperCase();
} else {
// Non-alphabetic characters
output += input[i];
}
}
return output;
},
/**
* Affine Cipher Encode operation.
*
* @author Matt C [matt@artemisbot.pw]
* @param {string} input
* @param {Object[]} args
* @returns {string}
*/
runAffineDec: function (input, args) {
var alphabet = "abcdefghijklmnopqrstuvwxyz",
a = args[0],
b = args[1],
output = "",
aModInv;
if (!/^\+?(0|[1-9]\d*)$/.test(a) || !/^\+?(0|[1-9]\d*)$/.test(b)) return "The values of a and b can only be integers.";
if (Utils.gcd(a, 26) !== 1) return "The value of a must be coprime to 26.";
// Calculates modular inverse of a
aModInv = Utils.modInv(a, 26);
for (var i = 0; i < input.length; i++) {
if (alphabet.indexOf(input[i]) >= 0) {
// Uses the affine decode function (y-b * A') % m = x (where m is length of the alphabet and A' is modular inverse)
output += alphabet[Utils.mod((alphabet.indexOf(input[i]) - b) * aModInv, 26)];
} else if (alphabet.indexOf(input[i].toLowerCase()) >= 0) {
// Same as above, accounting for uppercase
output += alphabet[Utils.mod((alphabet.indexOf(input[i].toLowerCase()) - b) * aModInv, 26)].toUpperCase();
} else {
// Non-alphabetic characters
output += input[i];
}
}
return output;
},
/**
* Atbash Cipher Encode operation.
*
* @author Matt C [matt@artemisbot.pw]
* @param {string} input
* @param {Object[]} args
* @returns {string}
*/
runAtbash: function (input, args) {
return Cipher.runAffineEnc(input, [25, 25]);
},
/**
* @constant