index: use secureRandom and add missing tests

index.js

@@ -1,5 +1,6 @@
 var CryptoJS = require('crypto-js')
 var crypto = require('crypto')
+var secureRandom = require('secure-random')
 
 var includeFolder = require('include-folder')
 var path = require('path')
@@ -32,10 +33,12 @@ BIP39.prototype.entropyToMnemonic = function(entropy) {
   return words.join(' ')
 }
 
-BIP39.prototype.generateMnemonic = function(strength) {
+BIP39.prototype.generateMnemonic = function(strength, rng) {
   strength = strength || 128
-  var entropy = crypto.randomBytes(strength/8).toString('hex')
-  return this.entropyToMnemonic(entropy)
+  rng = rng || secureRandom
+
+  var hex = rng.randomBuffer(strength / 8).toString('hex')
+  return this.entropyToMnemonic(hex)
 }
 
 BIP39.prototype.validate = function(mnemonic) {

package.json

@@ -16,7 +16,8 @@
   "dependencies": {
     "crypto-js": "^3.1.2-2",
     "require-json-tree": "~1.1.0",
-    "include-folder": "~0.7.0"
+    "include-folder": "~0.7.0",
+    "secure-random": "1.0.0"
   },
   "devDependencies": {
     "mocha": "^1.17.1",

test/index.js

@@ -27,6 +27,28 @@ describe('entropyToMnemonic', function() {
   })
 })
 
+describe('generateMnemonic', function() {
+  it('generates a mnemonic', function() {
+    var mnemonic = bip39.generateMnemonic(96)
+    var words = mnemonic.split(' ')
+
+    assert.equal(words.length, 9)
+  })
+
+  it('allows a custom RNG to be used', function() {
+    var rng = {
+      randomBuffer: function(size) {
+        var buffer = new Buffer(size)
+        buffer.fill(4) // guaranteed random
+        return buffer
+      }
+    }
+
+    var mnemonic = bip39.generateMnemonic(64, rng)
+    assert.equal(mnemonic, 'advice cage absurd amount doctor act')
+  })
+})
+
 describe('validate', function() {
   vectors.forEach(function(v, i) {
     it('passes check ' + i, function() {