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// Random number generator - requires a PRNG backend, e.g. prng4.js
var rng_state;
var rng_pool;
var rng_pptr;
// Initialize the pool with junk if needed.
if(rng_pool == null) {
rng_pool = new Array();
rng_pptr = 0;
var t;
if(window.crypto && window.crypto.getRandomValues) {
// Extract entropy (2048 bits) from RNG if available
var z = new Uint32Array(256);
window.crypto.getRandomValues(z);
for (t = 0; t < z.length; ++t)
rng_pool[rng_pptr++] = z[t] & 255;
}
// Use mouse events for entropy, if we do not have enough entropy by the time
// we need it, entropy will be generated by Math.random.
var onMouseMoveListener = function(ev) {
this.count = this.count || 0;
if (this.count >= 256 || rng_pptr >= rng_psize) {
if (window.removeEventListener)
window.removeEventListener("mousemove", onMouseMoveListener);
else if (window.detachEvent)
window.detachEvent("onmousemove", onMouseMoveListener);
return;
}
this.count += 1;
var mouseCoordinates = ev.x + ev.y;
rng_pool[rng_pptr++] = mouseCoordinates & 255;
};
if (window.addEventListener)
window.addEventListener("mousemove", onMouseMoveListener);
else if (window.attachEvent)
window.attachEvent("onmousemove", onMouseMoveListener);
}
function rng_get_byte() {
if(rng_state == null) {
rng_state = prng_newstate();
// At this point, we may not have collected enough entropy. If not, fall back to Math.random
while (rng_pptr < rng_psize) {
var random = Math.floor(65536 * Math.random());
rng_pool[rng_pptr++] = random & 255;
}
rng_state.init(rng_pool);
for(rng_pptr = 0; rng_pptr < rng_pool.length; ++rng_pptr)
rng_pool[rng_pptr] = 0;
rng_pptr = 0;
}
// TODO: allow reseeding after first request
return rng_state.next();
}
function rng_get_bytes(ba) {
var i;
for(i = 0; i < ba.length; ++i) ba[i] = rng_get_byte();
}
function SecureRandom() {}
SecureRandom.prototype.nextBytes = rng_get_bytes;
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