RC4 with support for ASCII Extended (Char Codes > 127)

rc4_ascii_extended.js

/*
 * RC4 symmetric cipher encryption/decryption
 *
 * @license Public Domain
 * @param string key - secret key for encryption/decryption
 * @param string str - string to be encrypted/decrypted
 * @return string
 */
 
Number.toASCII = function(i) {
	var t = document.createElement('div');
	t.innerHTML = '&#' + i;
	return t.innerHTML;
}

function rc4(key, str) {
	var s = [], j = 0, x, res = '';
	for (var i = 0; i < 256; i++) {
		s[i] = i;
	}
	for (i = 0; i < 256; i++) {
		j = (j + s[i] + key.charCodeAt(i % key.length)) % 256;
		x = s[i];
		s[i] = s[j];
		s[j] = x;
	}
	i = 0;
	j = 0;
	for (var y = 0; y < str.length; y++) {
		i = (i + 1) % 256;
		j = (j + s[i]) % 256;
		x = s[i];
		s[i] = s[j];
		s[j] = x;
		res += Number.toASCII(str.charCodeAt(y) ^ s[(s[i] + s[j]) % 256]);
	}
	return res;
}