Merge pull request #6 from ctso/master

Use better methods for generating entropy
travist · Aug 22, 2013 · 8d640a7 · 8d640a7
2 parents e9a9f31 + c3be58a
commit 8d640a7
Showing 1 changed file with 27 additions and 36 deletions.
diff --git a/jsbn/rng.js b/jsbn/rng.js
@@ -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();