70 lines
2.1 KiB
JavaScript
70 lines
2.1 KiB
JavaScript
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function RC4(key) {
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this.privateKey = keySetup(key);
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this.byteStream = byteStreamGenerator(this.privateKey.slice(0));
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}
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/**
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* Converts the text into an array of the characters numeric Unicode values
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* @param {String} text, the text to convert
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* @return {Array} the array of Unicode values
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*/
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function convert(text) {
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var codes = [];
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for (var i = 0, ii = text.length; i < ii; i++) { codes.push(text.charCodeAt(i)); }
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return codes;
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}
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/**
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* Sets up the key to use with the byte stream
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* @param {String} key, The key that you want to use
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* @return {Array}, the key stream which with be used in the byteStreamGenerator
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*/
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function keySetup(key) {
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var K = [...Array(256).keys()], j = 0, key = convert(key);
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for (var i = 0, ii = K.length; i < ii; i++) {
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j = (j + K[i] + key[i % key.length]) % 256;
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[K[i], K[j]] = [K[j], K[i]];
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}
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return K;
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}
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/**
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* byteStreamGenerator uses ES6 generators which will be 'XOR-ed' to encrypt and decrypt
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* @param {Array} K, the array generated from the keySetup
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* @yield {Integer}, the current value which will be 'XOR-ed' to encrypt or decrypt
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*/
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var byteStreamGenerator = function* (K) {
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var i = 0, j = 0;
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while (true) {
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i = (i + 1) % 256;
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j = (j + K[i]) % 256;
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[K[i], K[j]] = [K[j], K[i]];
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yield (K[(K[i] + K[j]) % 256]);
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}
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}
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/**
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* Encrypts the input text
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* @param {String} input, the text to encrypt
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* @return {String}, the encrypted text
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*/
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RC4.prototype.encrypt = function (input) {
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var outputText = '';
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for (var i = 0, ii = input.length; i < ii; i++) { outputText += ('00' + (input.charCodeAt(i) ^ this.byteStream.next().value).toString(16)).substr(-2); }
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return outputText;
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}
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/**
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* Decrypts the input text
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* @param {String} input, the text to decrypt
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* @return {String}, the decrypted text (if the same key was used)
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*/
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RC4.prototype.decrypt = function (input) {
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var outputText = '';
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input = input.match(/[a-z0-9]{2}/gi);
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for (var i = 0, ii = input.length; i < ii; i++) { outputText += String.fromCharCode((parseInt(input[i], 16) ^ byteStream.next().value)); }
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return outputText;
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}
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module.exports = RC4;
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