rc4.js
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(function () {
// Shortcuts
var C = CryptoJS;
var C_lib = C.lib;
var StreamCipher = C_lib.StreamCipher;
var C_algo = C.algo;
/**
* RC4 stream cipher algorithm.
*/
var RC4 = C_algo.RC4 = StreamCipher.extend({
_doReset: function () {
// Shortcuts
var key = this._key;
var keyWords = key.words;
var keySigBytes = key.sigBytes;
// Init sbox
var S = this._S = [];
for (var i = 0; i < 256; i++) {
S[i] = i;
}
// Key setup
for (var i = 0, j = 0; i < 256; i++) {
var keyByteIndex = i % keySigBytes;
var keyByte = (keyWords[keyByteIndex >>> 2] >>> (24 - (keyByteIndex % 4) * 8)) & 0xff;
j = (j + S[i] + keyByte) % 256;
// Swap
var t = S[i];
S[i] = S[j];
S[j] = t;
}
// Counters
this._i = this._j = 0;
},
_doProcessBlock: function (M, offset) {
M[offset] ^= generateKeystreamWord.call(this);
},
keySize: 256/32,
ivSize: 0
});
function generateKeystreamWord() {
// Shortcuts
var S = this._S;
var i = this._i;
var j = this._j;
// Generate keystream word
var keystreamWord = 0;
for (var n = 0; n < 4; n++) {
i = (i + 1) % 256;
j = (j + S[i]) % 256;
// Swap
var t = S[i];
S[i] = S[j];
S[j] = t;
keystreamWord |= S[(S[i] + S[j]) % 256] << (24 - n * 8);
}
// Update counters
this._i = i;
this._j = j;
return keystreamWord;
}
/**
* Shortcut functions to the cipher's object interface.
*
* @example
*
* var ciphertext = CryptoJS.RC4.encrypt(message, key, cfg);
* var plaintext = CryptoJS.RC4.decrypt(ciphertext, key, cfg);
*/
C.RC4 = StreamCipher._createHelper(RC4);
/**
* Modified RC4 stream cipher algorithm.
*/
var RC4Drop = C_algo.RC4Drop = RC4.extend({
/**
* Configuration options.
*
* @property {number} drop The number of keystream words to drop. Default 192
*/
cfg: RC4.cfg.extend({
drop: 192
}),
_doReset: function () {
RC4._doReset.call(this);
// Drop
for (var i = this.cfg.drop; i > 0; i--) {
generateKeystreamWord.call(this);
}
}
});
/**
* Shortcut functions to the cipher's object interface.
*
* @example
*
* var ciphertext = CryptoJS.RC4Drop.encrypt(message, key, cfg);
* var plaintext = CryptoJS.RC4Drop.decrypt(ciphertext, key, cfg);
*/
C.RC4Drop = StreamCipher._createHelper(RC4Drop);
}());