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Use better methods for generating entropy #6

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merged 3 commits into from
Aug 22, 2013
Merged

Use better methods for generating entropy #6

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a9c9926
Use crypto.getRandomValues for RNG if available
ctso Aug 20, 2013
2cdd2f7
Use better entropy generation methods
ctso Aug 20, 2013
c3be58a
Initialize Uint32Array before getRandomValues
ctso Aug 20, 2013
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63 changes: 27 additions & 36 deletions jsbn/rng.js
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Original file line number Diff line number Diff line change
@@ -1,58 +1,49 @@
// Random number generator - requires a PRNG backend, e.g. prng4.js

// For best results, put code like
// <body onClick='rng_seed_time();' onKeyPress='rng_seed_time();'>
// in your main HTML document.

var rng_state;
var rng_pool;
var rng_pptr;

// Mix in a 32-bit integer into the pool
function rng_seed_int(x) {
rng_pool[rng_pptr++] ^= x & 255;
rng_pool[rng_pptr++] ^= (x >> 8) & 255;
rng_pool[rng_pptr++] ^= (x >> 16) & 255;
rng_pool[rng_pptr++] ^= (x >> 24) & 255;
if(rng_pptr >= rng_psize) rng_pptr -= rng_psize;
}

// Mix in the current time (w/milliseconds) into the pool
function rng_seed_time() {
rng_seed_int(new Date().getTime());
}

// Initialize the pool with junk if needed.
if(rng_pool == null) {
rng_pool = new Array();
rng_pptr = 0;
var t;
if(navigator.appName == "Netscape" && navigator.appVersion < "5" && window.crypto) {
// Extract entropy (256 bits) from NS4 RNG if available
var z = window.crypto.random(32);
for(t = 0; t < z.length; ++t)
rng_pool[rng_pptr++] = z.charCodeAt(t) & 255;
}
while(rng_pptr < rng_psize) { // extract some randomness from Math.random()
t = Math.floor(65536 * Math.random());
rng_pool[rng_pptr++] = t >>> 8;
rng_pool[rng_pptr++] = t & 255;
}
rng_pptr = 0;
rng_seed_time();
//rng_seed_int(window.screenX);
//rng_seed_int(window.screenY);
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) {
window.removeEventListener("mousemove", onMouseMoveListener);
return;
}
this.count += 1;
var mouseCoordinates = ev.x + ev.y;
rng_pool[rng_pptr++] = mouseCoordinates & 255;
};

window.addEventListener("mousemove", onMouseMoveListener);
}

function rng_get_byte() {
if(rng_state == null) {
rng_seed_time();
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;
//rng_pool = null;
}
// TODO: allow reseeding after first request
return rng_state.next();
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