/*!
* Random number generator with ArcFour PRNG
*
* NOTE: For best results, put code like
* <body onclick='SecureRandom.seedTime();' onkeypress='SecureRandom.seedTime();'>
* in your main HTML document.
*
* Copyright Tom Wu, bitaddress.org BSD License.
* http://www-cs-students.stanford.edu/~tjw/jsbn/LICENSE
*/
(function () {
// Constructor function of Global SecureRandom object
var sr = window.SecureRandom = function () { };
// Properties
sr.state;
sr.pool;
sr.pptr;
sr.poolCopyOnInit;
// Pool size must be a multiple of 4 and greater than 32.
// An array of bytes the size of the pool will be passed to init()
sr.poolSize = 256;
// --- object methods ---
// public method
// ba: byte array
sr.prototype.nextBytes = function (ba) {
var i;
if (window.crypto && window.crypto.getRandomValues && window.Uint8Array) {
try {
var rvBytes = new Uint8Array(ba.length);
window.crypto.getRandomValues(rvBytes);
for (i = 0; i < ba.length; ++i)
ba[i] = sr.getByte() ^ rvBytes[i];
return;
} catch (e) {
alert(e);
}
}
for (i = 0; i < ba.length; ++i) ba[i] = sr.getByte();
};
// --- static methods ---
// Mix in the current time (w/milliseconds) into the pool
// NOTE: this method should be called from body click/keypress event handlers to increase entropy
sr.seedTime = function () {
sr.seedInt(new Date().getTime());
}
sr.getByte = function () {
if (sr.state == null) {
sr.seedTime();
sr.state = sr.ArcFour(); // Plug in your RNG constructor here
sr.state.init(sr.pool);
sr.poolCopyOnInit = [];
for (sr.pptr = 0; sr.pptr < sr.pool.length; ++sr.pptr)
sr.poolCopyOnInit[sr.pptr] = sr.pool[sr.pptr];
sr.pptr = 0;
}
// TODO: allow reseeding after first request
return sr.state.next();
}
// Mix in a 32-bit integer into the pool
sr.seedInt = function (x) {
sr.seedInt8(x);
sr.seedInt8((x >> 8));
sr.seedInt8((x >> 16));
sr.seedInt8((x >> 24));
}
// Mix in a 16-bit integer into the pool
sr.seedInt16 = function (x) {
sr.seedInt8(x);
sr.seedInt8((x >> 8));
}
// Mix in a 8-bit integer into the pool
sr.seedInt8 = function (x) {
sr.pool[sr.pptr++] ^= x & 255;
if (sr.pptr >= sr.poolSize) sr.pptr -= sr.poolSize;
}
// Arcfour is a PRNG
sr.ArcFour = function () {
function Arcfour() {
this.i = 0;
this.j = 0;
this.S = new Array();
}
// Initialize arcfour context from key, an array of ints, each from [0..255]
function ARC4init(key) {
var i, j, t;
for (i = 0; i < 256; ++i)
this.S[i] = i;
j = 0;
for (i = 0; i < 256; ++i) {
j = (j + this.S[i] + key[i % key.length]) & 255;
t = this.S[i];
this.S[i] = this.S[j];
this.S[j] = t;
}
this.i = 0;
this.j = 0;
}
function ARC4next() {
var t;
this.i = (this.i + 1) & 255;
this.j = (this.j + this.S[this.i]) & 255;
t = this.S[this.i];
this.S[this.i] = this.S[this.j];
this.S[this.j] = t;
return this.S[(t + this.S[this.i]) & 255];
}
Arcfour.prototype.init = ARC4init;
Arcfour.prototype.next = ARC4next;
return new Arcfour();
};
// Initialize the pool with junk if needed.
if (sr.pool == null) {
sr.pool = new Array();
sr.pptr = 0;
var t;
if (window.crypto && window.crypto.getRandomValues && window.Uint8Array) {
try {
// Use webcrypto if available
var ua = new Uint8Array(sr.poolSize);
window.crypto.getRandomValues(ua);
for (t = 0; t < sr.poolSize; ++t)
sr.pool[sr.pptr++] = ua[t];
} catch (e) { alert(e); }
}
while (sr.pptr < sr.poolSize) { // extract some randomness from Math.random()
t = Math.floor(65536 * Math.random());
sr.pool[sr.pptr++] = t >>> 8;
sr.pool[sr.pptr++] = t & 255;
}
sr.pptr = Math.floor(sr.poolSize * Math.random());
sr.seedTime();
// entropy
var entropyStr = "";
// screen size and color depth: ~4.8 to ~5.4 bits
entropyStr += (window.screen.height * window.screen.width * window.screen.colorDepth);
entropyStr += (window.screen.availHeight * window.screen.availWidth * window.screen.pixelDepth);
// time zone offset: ~4 bits
var dateObj = new Date();
var timeZoneOffset = dateObj.getTimezoneOffset();
entropyStr += timeZoneOffset;
// user agent: ~8.3 to ~11.6 bits
entropyStr += navigator.userAgent;
// browser plugin details: ~16.2 to ~21.8 bits
var pluginsStr = "";
for (var i = 0; i < navigator.plugins.length; i++) {
pluginsStr += navigator.plugins[i].name + " " + navigator.plugins[i].filename + " " + navigator.plugins[i].description + " " + navigator.plugins[i].version + ", ";
}
var mimeTypesStr = "";
for (var i = 0; i < navigator.mimeTypes.length; i++) {
mimeTypesStr += navigator.mimeTypes[i].description + " " + navigator.mimeTypes[i].type + " " + navigator.mimeTypes[i].suffixes + ", ";
}
entropyStr += pluginsStr + mimeTypesStr;
// cookies and storage: 1 bit
entropyStr += navigator.cookieEnabled + typeof (sessionStorage) + typeof (localStorage);
// language: ~7 bit
entropyStr += navigator.language;
// history: ~2 bit
entropyStr += window.history.length;
// location
entropyStr += window.location;
var entropyBytes = Crypto.SHA256(entropyStr, { asBytes: true });
for (var i = 0 ; i < entropyBytes.length ; i++) {
sr.seedInt8(entropyBytes[i]);
}
}
})();