120 lines
2.4 KiB
JavaScript
120 lines
2.4 KiB
JavaScript
import {
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StreamCipher,
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} from './cipher-core.js';
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function generateKeystreamWord() {
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// Shortcuts
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const S = this._S;
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let i = this._i;
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let j = this._j;
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// Generate keystream word
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let keystreamWord = 0;
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for (let n = 0; n < 4; n += 1) {
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i = (i + 1) % 256;
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j = (j + S[i]) % 256;
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// Swap
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const t = S[i];
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S[i] = S[j];
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S[j] = t;
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keystreamWord |= S[(S[i] + S[j]) % 256] << (24 - n * 8);
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}
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// Update counters
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this._i = i;
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this._j = j;
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return keystreamWord;
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}
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/**
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* RC4 stream cipher algorithm.
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*/
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export class RC4Algo extends StreamCipher {
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_doReset() {
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// Shortcuts
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const key = this._key;
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const keyWords = key.words;
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const keySigBytes = key.sigBytes;
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// Init sbox
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this._S = [];
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const S = this._S;
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for (let i = 0; i < 256; i += 1) {
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S[i] = i;
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}
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// Key setup
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for (let i = 0, j = 0; i < 256; i += 1) {
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const keyByteIndex = i % keySigBytes;
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const keyByte = (keyWords[keyByteIndex >>> 2] >>> (24 - (keyByteIndex % 4) * 8)) & 0xff;
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j = (j + S[i] + keyByte) % 256;
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// Swap
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const t = S[i];
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S[i] = S[j];
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S[j] = t;
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}
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// Counters
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this._j = 0;
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this._i = this._j;
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}
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_doProcessBlock(M, offset) {
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const _M = M;
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_M[offset] ^= generateKeystreamWord.call(this);
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}
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}
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RC4Algo.keySize = 256 / 32;
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RC4Algo.ivSize = 0;
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/**
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* Shortcut functions to the cipher's object interface.
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*
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* @example
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*
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* var ciphertext = CryptoJS.RC4.encrypt(message, key, cfg);
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* var plaintext = CryptoJS.RC4.decrypt(ciphertext, key, cfg);
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*/
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export const RC4 = StreamCipher._createHelper(RC4Algo);
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/**
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* Modified RC4 stream cipher algorithm.
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*/
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export class RC4DropAlgo extends RC4Algo {
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constructor(...args) {
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super(...args);
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/**
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* Configuration options.
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*
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* @property {number} drop The number of keystream words to drop. Default 192
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*/
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Object.assign(this.cfg, { drop: 192 });
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}
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_doReset() {
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super._doReset.call(this);
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// Drop
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for (let i = this.cfg.drop; i > 0; i -= 1) {
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generateKeystreamWord.call(this);
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}
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}
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}
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/**
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* Shortcut functions to the cipher's object interface.
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*
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* @example
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*
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* var ciphertext = CryptoJS.RC4Drop.encrypt(message, key, cfg);
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* var plaintext = CryptoJS.RC4Drop.decrypt(ciphertext, key, cfg);
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*/
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export const RC4Drop = StreamCipher._createHelper(RC4DropAlgo);
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