diff --git a/src/crypto.js b/src/crypto.js
index 64d69e6..6937f05 100644
--- a/src/crypto.js
+++ b/src/crypto.js
@@ -1,4 +1,5 @@
 // Crypto, crypto, where art thou crypto
+var assert = require('assert')
 var CryptoJS = require('crypto-js')
 var crypto = require('crypto')
 var convert = require('./convert')
@@ -32,9 +33,23 @@ function sha256(buffer) {
   return crypto.createHash('sha256').update(buffer).digest()
 }
 
+// FIXME: Name not consistent with others
+function HmacSHA512(data, secret) {
+  assert(Buffer.isBuffer(data), 'Expected Buffer for data, got ' + data)
+  assert(Buffer.isBuffer(secret), 'Expected Buffer for secret, got ' + secret)
+
+  var dataWords = convert.bytesToWordArray(data)
+  var secretWords = convert.bytesToWordArray(secret)
+
+  var hash = CryptoJS.HmacSHA512(dataWords, secretWords)
+
+  return new Buffer(convert.wordArrayToBytes(hash))
+}
+
 module.exports = {
   sha1: sha1,
   sha256: sha256,
   hash160: hash160,
-  hash256: hash256
+  hash256: hash256,
+  HmacSHA512: HmacSHA512
 }
diff --git a/src/hdwallet.js b/src/hdwallet.js
index 513d08a..c0d68db 100644
--- a/src/hdwallet.js
+++ b/src/hdwallet.js
@@ -4,7 +4,6 @@ var convert = require('./convert')
 
 var Address = require('./address')
 var BigInteger = require('bigi')
-var CJS = require('crypto-js')
 var crypto = require('./crypto')
 var ECKey = require('./eckey').ECKey
 var ECPubKey = require('./eckey').ECPubKey
@@ -13,18 +12,6 @@ var networks = require('./networks')
 var sec = require('./sec')
 var ecparams = sec("secp256k1")
 
-function HmacSHA512(data, secret) {
-  assert(Buffer.isBuffer(data))
-  assert(Buffer.isBuffer(secret))
-
-  var dataWords = convert.bytesToWordArray(data)
-  var secretWords = convert.bytesToWordArray(secret)
-
-  var hash = CJS.HmacSHA512(dataWords, secretWords)
-
-  return new Buffer(convert.wordArrayToBytes(hash))
-}
-
 function HDWallet(seed, networkString) {
   if (seed == undefined) return; // FIXME: Boo, should be stricter
 
@@ -34,7 +21,7 @@ function HDWallet(seed, networkString) {
     throw new Error("Unknown network: " + this.network)
   }
 
-  var I = HmacSHA512(seed, HDWallet.MASTER_SECRET)
+  var I = crypto.HmacSHA512(seed, HDWallet.MASTER_SECRET)
   var IL = I.slice(0, 32)
   var IR = I.slice(32)
 
@@ -217,7 +204,7 @@ HDWallet.prototype.derive = function(index) {
     ])
   }
 
-  var I = HmacSHA512(data, this.chaincode)
+  var I = crypto.HmacSHA512(data, this.chaincode)
   var IL = I.slice(0, 32)
   var IR = I.slice(32)
 
diff --git a/test/crypto.js b/test/crypto.js
index 9b2068b..ff414d7 100644
--- a/test/crypto.js
+++ b/test/crypto.js
@@ -46,4 +46,18 @@ describe('Crypto', function() {
       })
     })
   })
+
+  describe('HMAC SHA512', function() {
+    it('matches the test vector', function() {
+      fixture.before.hex.forEach(function(hex, i) {
+        var data = new Buffer(hex, 'hex')
+        var secret = new Buffer(fixture.after.hmacsha512.secret)
+
+        var actual = crypto.HmacSHA512(data, secret)
+        var expected = fixture.after.hmacsha512.hash[i]
+
+        assert.equal(actual.toString('hex'), expected)
+      })
+    })
+  })
 })
diff --git a/test/fixtures/crypto.js b/test/fixtures/crypto.js
index 790fa9e..1600a06 100644
--- a/test/fixtures/crypto.js
+++ b/test/fixtures/crypto.js
@@ -32,6 +32,15 @@ module.exports = {
       '04abc8821a06e5a30937967d11ad10221cb5ac3b5273e434f1284ee87129a061',
       '12a3ae445661ce5dee78d0650d33362dec29c4f82af05e7e57fb595bbbacf0ca',
       'a7fb8276035057ed6479c5f2305a96da100ac43f0ac10f277e5ab8c5457429da'
-    ]
+    ],
+    hmacsha512: {
+      secret: 'vires is numeris',
+      hash: [
+        '4c0595aed1f5d066ea9f797727c060eb86cb55ff29d4d4fd2cd0ad3a012386763aea604c030619c79aa7fd8d03cda1b73a9ebd17906a3d2a350108d1a98b24ac',
+        'f80b90d63b804b3d2ab03b9bfb3ac94ee271352eb8bddfb6b4f5cf2a4fc9176acea35f517728e64943d1eb8af1e4674a114082c81bc8874d88b408b3b406d6a4',
+        '134cf60c30a5cd412c7a5cd6c3f878279e139b47c19550b7456fa137fbf90e580ae0a923a22052f42ec801ac658db32821e271161b563eac4926285ba6b8f410',
+        '7dee95aa3c462d3eb7ecb61536cb215e471d1fa73d8643a967905946e26c536588c5058abd5a049a22b987db95a7fb420f3bff12359dc53d03d7ce7df714e029'
+      ]
+    }
   }
 }