mirror of https://github.com/gchq/CyberChef.git
103 lines
3.0 KiB
JavaScript
103 lines
3.0 KiB
JavaScript
/**
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* @author Matt C [matt@artemisbot.uk]
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* @copyright Crown Copyright 2018
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* @license Apache-2.0
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*/
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import Operation from "../Operation.mjs";
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import OperationError from "../errors/OperationError.mjs";
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/**
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* Vigenère Decode operation
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*/
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class VigenèreDecode extends Operation {
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/**
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* VigenèreDecode constructor
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*/
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constructor() {
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super();
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this.name = "Vigenère Decode";
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this.module = "Ciphers";
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this.description = "The Vigenere cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. It is a simple form of polyalphabetic substitution.";
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this.infoURL = "https://wikipedia.org/wiki/Vigenère_cipher";
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this.inputType = "string";
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this.outputType = "string";
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this.args = [
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{
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"name": "Key",
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"type": "string",
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"value": ""
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}
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];
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}
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/**
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* @param {string} input
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* @param {Object[]} args
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* @returns {string}
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*/
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run(input, args) {
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const alphabet = "abcdefghijklmnopqrstuvwxyz",
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key = args[0].toLowerCase();
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let output = "",
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fail = 0,
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keyIndex,
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msgIndex,
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chr;
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if (!key) throw new OperationError("No key entered");
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if (!/^[a-zA-Z]+$/.test(key)) throw new OperationError("The key must consist only of letters");
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for (let i = 0; i < input.length; i++) {
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if (alphabet.indexOf(input[i]) >= 0) {
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chr = key[(i - fail) % key.length];
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keyIndex = alphabet.indexOf(chr);
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msgIndex = alphabet.indexOf(input[i]);
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// Subtract indexes from each other, add 26 just in case the value is negative,
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// modulo to remove if necessary
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output += alphabet[(msgIndex - keyIndex + alphabet.length) % 26];
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} else if (alphabet.indexOf(input[i].toLowerCase()) >= 0) {
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chr = key[(i - fail) % key.length].toLowerCase();
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keyIndex = alphabet.indexOf(chr);
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msgIndex = alphabet.indexOf(input[i].toLowerCase());
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output += alphabet[(msgIndex + alphabet.length - keyIndex) % 26].toUpperCase();
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} else {
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output += input[i];
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fail++;
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}
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}
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return output;
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}
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/**
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* Highlight Vigenère Decode
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*
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* @param {Object[]} pos
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* @param {number} pos[].start
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* @param {number} pos[].end
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* @param {Object[]} args
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* @returns {Object[]} pos
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*/
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highlight(pos, args) {
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return pos;
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}
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/**
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* Highlight Vigenère Decode in reverse
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*
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* @param {Object[]} pos
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* @param {number} pos[].start
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* @param {number} pos[].end
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* @param {Object[]} args
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* @returns {Object[]} pos
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*/
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highlightReverse(pos, args) {
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return pos;
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}
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}
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export default VigenèreDecode;
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