rc4

rc4.js

/**
 * Encrypt given plain text using the key with RC4 algorithm.
 * All parameters and return value are in binary format.
 *
 * @param string key - secret key for encryption
 * @param string pt - plain text to be encrypted
 * @return string
 */
exports = module.exports = function rc4(key, pt) {
    s = new Array();
    for (var i = 0; i < 256; i++) {
        s[i] = i;
    }
    var j = 0;
    var x;
    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;
    var ct = '';
    for (var y = 0; y < pt.length; y++) {
        i = (i + 1) % 256;
        j = (j + s[i]) % 256;
        x = s[i];
        s[i] = s[j];
        s[j] = x;
        ct += String.fromCharCode(pt.charCodeAt(y) ^ s[(s[i] + s[j]) % 256]);
    }
    return ct;
}

test.js

var rc4 = require('./rc4');
// RC4 PRIVATE KEY
var key = '123456789';

var file = 'test123456';

// Encrypt
var encfile = rc4(key, file);
console.log(encfile);

// Decrypt
var decfile = rc4(key, encfile);
console.log(decfile);