diff --git a/lib/bip70/paymentrequest.js b/lib/bip70/paymentrequest.js
index 1b72fa59..858d56b1 100644
--- a/lib/bip70/paymentrequest.js
+++ b/lib/bip70/paymentrequest.js
@@ -8,6 +8,7 @@
 
 var assert = require('assert');
 var util = require('../utils/util');
+var co = require('../utils/co');
 var crypto = require('../crypto/crypto');
 var x509 = require('./x509');
 var PEM = require('../utils/pem');
@@ -226,6 +227,34 @@ PaymentRequest.prototype.verifyChain = function verifyChain() {
   return x509.verifyChain(this.getChain());
 };
 
+PaymentRequest.prototype.verifyAsync = co(function* verifyAsync() {
+  var alg, msg, sig, chain;
+
+  if (!this.pkiType || this.pkiType === 'none')
+    return true;
+
+  if (!this.signature)
+    return false;
+
+  alg = this.getAlgorithm();
+
+  if (!alg)
+    return false;
+
+  msg = this.signatureData();
+  sig = this.signature;
+  chain = this.getChain();
+
+  return yield x509.verifySubjectAsync(alg.hash, msg, sig, chain);
+});
+
+PaymentRequest.prototype.verifyChainAsync = co(function* verifyChain() {
+  if (!this.pkiType || this.pkiType === 'none')
+    return true;
+
+  return yield x509.verifyChainAsync(this.getChain());
+});
+
 PaymentRequest.prototype.getCA = function getCA() {
   var chain, root;
 
diff --git a/lib/bip70/pk.js b/lib/bip70/pk.js
index 681b05b2..26a27d04 100644
--- a/lib/bip70/pk.js
+++ b/lib/bip70/pk.js
@@ -7,6 +7,7 @@
 'use strict';
 
 var pk = require('../crypto/pk');
+var co = require('../utils/co');
 
 exports._verify = function verify(hash, msg, sig, key) {
   switch (key.alg) {
@@ -41,3 +42,37 @@ exports.sign = function sign(hash, msg, key) {
       throw new Error('Unsupported algorithm.');
   }
 };
+
+exports._verifyAsync = co(function* verifyAsync(hash, msg, sig, key) {
+  switch (key.alg) {
+    case 'dsa':
+      return yield pk.dsa.verifyAsync(hash, msg, sig, key.data, key.params);
+    case 'rsa':
+      return yield pk.rsa.verifyAsync(hash, msg, sig, key.data);
+    case 'ecdsa':
+      return yield pk.ecdsa.verifyAsync(key.curve, hash, msg, sig, key.data);
+    default:
+      throw new Error('Unsupported algorithm.');
+  }
+});
+
+exports.verifyAsync = co(function* verifyAsync(hash, msg, sig, key) {
+  try {
+    return yield exports._verifyAsync(hash, msg, sig, key);
+  } catch (e) {
+    return false;
+  }
+});
+
+exports.signAsync = co(function* signAsync(hash, msg, key) {
+  switch (key.alg) {
+    case 'dsa':
+      return yield pk.dsa.signAsync(hash, msg, key.data, key.params);
+    case 'rsa':
+      return yield pk.rsa.signAsync(hash, msg, key.data);
+    case 'ecdsa':
+      return yield pk.ecdsa.signAsync(key.curve, hash, msg, key.data);
+    default:
+      throw new Error('Unsupported algorithm.');
+  }
+});
diff --git a/lib/bip70/x509.js b/lib/bip70/x509.js
index 180b15a4..61e02064 100644
--- a/lib/bip70/x509.js
+++ b/lib/bip70/x509.js
@@ -12,6 +12,7 @@ var PEM = require('../utils/pem');
 var util = require('../utils/util');
 var crypto = require('../crypto/crypto');
 var pk = require('./pk');
+var co = require('../utils/co');
 var x509 = exports;
 
 x509.getSubjectOID = function getSubjectOID(cert, oid) {
@@ -177,11 +178,11 @@ x509.getPublicKey = function getPublicKey(cert) {
 
 x509.verifyTime = function verifyTime(cert) {
   var time = cert.tbs.validity;
-  var now = Math.floor(Date.now() / 1000);
+  var now = util.now();
   return now > time.notBefore && now < time.notAfter;
 };
 
-x509.signSubject = function signSubject(hash, msg, key, chain) {
+x509.getSigningKey = function getSigningKey(key, chain) {
   var cert, pub, curve;
 
   assert(chain.length !== 0, 'No chain available.');
@@ -210,10 +211,20 @@ x509.signSubject = function signSubject(hash, msg, key, chain) {
     };
   }
 
-  return pk.sign(hash, msg, key);
+  return key;
 };
 
-x509.verifySubject = function verifySubject(hash, msg, sig, chain) {
+x509.signSubject = function signSubject(hash, msg, key, chain) {
+  var priv = x509.getSigningKey(key, chain);
+  return pk.sign(hash, msg, priv);
+};
+
+x509.signSubjectAsync = co(function* signSubjectAsync(hash, msg, key, chain) {
+  var priv = x509.getSigningKey(key, chain);
+  return yield pk.signAsync(hash, msg, priv);
+});
+
+x509.getVerifyKey = function getVerifyKey(chain) {
   var cert, key;
 
   if (chain.length === 0)
@@ -229,27 +240,82 @@ x509.verifySubject = function verifySubject(hash, msg, sig, chain) {
   if (!key)
     return false;
 
+  return key;
+};
+
+x509.verifySubject = function verifySubject(hash, msg, sig, chain) {
+  var key = x509.getVerifyKey(chain);
   return pk.verify(hash, msg, sig, key);
 };
 
-x509.verifyChain = function verifyChain(chain) {
+x509.verifySubjectAsync = co(function* verifySubjectAsync(hash, msg, sig, chain) {
+  var key = x509.getVerifyKey(chain);
+  return yield pk.verifyAsync(hash, msg, sig, key);
+});
+
+x509.parseChain = function parseChain(chain) {
+  var certs = [];
+  var i, cert;
+
+  for (i = 0; i < chain.length; i++) {
+    cert = x509.parse(chain[i]);
+
+    if (!cert)
+      return;
+
+    certs.push(cert);
+  }
+
+  return certs;
+};
+
+x509.verifyTimes = function verifyTimes(chain) {
+  var i, cert;
+
+  for (i = 0; i < chain.length; i++) {
+    cert = chain[i];
+    if (!x509.verifyTime(cert))
+      return false;
+  }
+
+  return true;
+};
+
+x509.verifyTrust = function verifyTrust(chain) {
+  var i, cert;
+
+  // If trust hasn't been
+  // setup, just return.
+  if (x509.allowUntrusted)
+    return true;
+
+  // Make sure we trust one
+  // of the certs in the chain.
+  for (i = 0; i < chain.length; i++) {
+    cert = chain[i];
+
+    // If any certificate in the chain
+    // is trusted, assume we also trust
+    // the parent.
+    if (x509.isTrusted(cert))
+      return true;
+  }
+
+  // No trusted certs present.
+  return false;
+};
+
+x509.verifyChain = function verifyChain(certs) {
+  var chain = x509.parseChain(certs);
   var i, child, parent, alg, key, sig, msg;
 
-  chain = chain.slice();
+  if (!chain)
+    return false;
 
   // Parse certificates and
   // check validity time.
-  for (i = 0; i < chain.length; i++) {
-    child = x509.parse(chain[i]);
-
-    if (!child)
-      return false;
-
-    chain[i] = child;
-
-    if (!x509.verifyTime(child))
-      return false;
-  }
+  if (!x509.verifyTimes(chain))
+    return false;
 
   // Verify signatures.
   for (i = 1; i < chain.length; i++) {
@@ -271,26 +337,47 @@ x509.verifyChain = function verifyChain(chain) {
       return false;
   }
 
-  // If trust hasn't been
-  // setup, just return.
-  if (x509.allowUntrusted)
-    return true;
+  // Make sure we trust one
+  // of the certs in the chain.
+  return x509.verifyTrust(chain);
+};
+
+x509.verifyChainAsync = co(function* verifyChainAsync(certs) {
+  var chain = x509.parseChain(certs);
+  var i, child, parent, alg, key, sig, msg;
+
+  if (!chain)
+    return false;
+
+  // Parse certificates and
+  // check validity time.
+  if (!x509.verifyTimes(chain))
+    return false;
+
+  // Verify signatures.
+  for (i = 1; i < chain.length; i++) {
+    child = chain[i - 1];
+    parent = chain[i];
+
+    alg = x509.getSigAlgorithm(child);
+    msg = child.tbs.raw;
+    sig = child.sig;
+    key = x509.getPublicKey(parent);
+
+    if (!alg || !alg.hash)
+      return false;
+
+    if (!key)
+      return false;
+
+    if (!(yield pk.verifyAsync(alg.hash, msg, sig, key)))
+      return false;
+  }
 
   // Make sure we trust one
   // of the certs in the chain.
-  for (i = 0; i < chain.length; i++) {
-    child = chain[i];
-
-    // If any certificate in the chain
-    // is trusted, assume we also trust
-    // the parent.
-    if (x509.isTrusted(child))
-      return true;
-  }
-
-  // No trusted certs present.
-  return false;
-};
+  return x509.verifyTrust(chain);
+});
 
 function isHash(data) {
   if (typeof data === 'string')
diff --git a/lib/blockchain/chain.js b/lib/blockchain/chain.js
index 7dc13e1f..8fe4d1d0 100644
--- a/lib/blockchain/chain.js
+++ b/lib/blockchain/chain.js
@@ -1318,6 +1318,8 @@ Chain.prototype._add = co(function* add(block) {
           'error parsing message',
           100);
       }
+      if (util.isBrowser)
+        yield block.cacheHashes();
     }
 
     // Update the block height early
diff --git a/lib/crypto/aes.js b/lib/crypto/aes.js
index 7243efbb..2e61e881 100644
--- a/lib/crypto/aes.js
+++ b/lib/crypto/aes.js
@@ -33,14 +33,22 @@ function AESKey(key, bits) {
   this.userKey = key;
   this.bits = bits;
 
-  if (this.bits === 128)
-    this.rounds = 10;
-  else if (this.bits === 192)
-    this.rounds = 12;
-  else if (this.bits === 256)
-    this.rounds = 14;
-  else
-    throw new Error('Bad key size.');
+  switch (this.bits) {
+    case 128:
+      this.rounds = 10;
+      break;
+    case 192:
+      this.rounds = 12;
+      break;
+    case 256:
+      this.rounds = 14;
+      break;
+    default:
+      throw new Error('Bad key size.');
+  }
+
+  assert(Buffer.isBuffer(key));
+  assert(key.length === this.bits / 8);
 
   this.decryptKey = null;
   this.encryptKey = null;
@@ -688,6 +696,8 @@ AES.ecb = {};
  */
 
 AES.ecb.encrypt = function encrypt(data, key) {
+  assert(Buffer.isBuffer(data));
+  assert(key.length === 32);
   return AES.encrypt(data, key, null, 256, 'ecb');
 };
 
@@ -699,6 +709,8 @@ AES.ecb.encrypt = function encrypt(data, key) {
  */
 
 AES.ecb.decrypt = function decrypt(data, key) {
+  assert(Buffer.isBuffer(data));
+  assert(key.length === 32);
   return AES.decrypt(data, key, null, 256, 'ecb');
 };
 
@@ -717,6 +729,9 @@ AES.cbc = {};
  */
 
 AES.cbc.encrypt = function encrypt(data, key, iv) {
+  assert(Buffer.isBuffer(data));
+  assert(key.length === 32);
+  assert(iv.length === 16);
   return AES.encrypt(data, key, iv, 256, 'cbc');
 };
 
@@ -729,6 +744,9 @@ AES.cbc.encrypt = function encrypt(data, key, iv) {
  */
 
 AES.cbc.decrypt = function decrypt(data, key, iv) {
+  assert(Buffer.isBuffer(data));
+  assert(key.length === 32);
+  assert(iv.length === 16);
   return AES.decrypt(data, key, iv, 256, 'cbc');
 };
 
diff --git a/lib/crypto/backend-browser.js b/lib/crypto/backend-browser.js
index a41b6ee9..fa4bc175 100644
--- a/lib/crypto/backend-browser.js
+++ b/lib/crypto/backend-browser.js
@@ -4,57 +4,168 @@
  * https://github.com/bcoin-org/bcoin
  */
 
-/* jshint worker: true */
-
 'use strict';
 
 var assert = require('assert');
 var hashjs = require('hash.js');
+var util = require('../utils/util');
 var aes = require('./aes');
+var global = util.global;
+var crypto = global.crypto || global.msCrypto || {};
+var subtle = crypto.subtle && crypto.subtle.importKey ? crypto.subtle : {};
 var backend = exports;
-var global, crypto, subtle;
 
-global = (function() {
-  if (typeof window !== 'undefined')
-    return window;
+/*
+ * Hashing
+ */
 
-  if (typeof self !== 'undefined')
-    return self;
-
-  throw new Error('No global found.');
-})();
-
-crypto = global.crypto || global.msCrypto;
-subtle = crypto ? crypto.subtle : null;
-
-backend.hash = function hash(alg, data) {
-  return new Buffer(hashjs[alg]().update(data).digest());
+backend.hash = function _hash(alg, data) {
+  var hash = hashjs[alg];
+  assert(hash != null, 'Unknown algorithm.');
+  return new Buffer(hash().update(data).digest());
 };
 
-backend.hmac = function hmac(alg, data, salt) {
+backend.ripemd160 = function ripemd160(data) {
+  return backend.hash('ripemd160', data);
+};
+
+backend.sha1 = function sha1(data) {
+  return backend.hash('sha1', data);
+};
+
+backend.sha256 = function sha256(data) {
+  return backend.hash('sha256', data);
+};
+
+backend.hash160 = function hash160(data) {
+  return backend.ripemd160(backend.sha256(data));
+};
+
+backend.hash256 = function hash256(data) {
+  return backend.sha256(backend.sha256(data));
+};
+
+backend.hmac = function _hmac(alg, data, key) {
   var hash = hashjs[alg];
   var hmac;
 
   assert(hash != null, 'Unknown algorithm.');
 
-  hmac = hashjs.hmac(hash, salt);
+  hmac = hashjs.hmac(hash, key);
 
   return new Buffer(hmac.update(data).digest());
 };
 
-backend.pbkdf2 = null;
+backend.hashAsync = function hashAsync(alg, data) {
+  var name = backend.getHash(alg);
+  var result;
+
+  if (!name) {
+    try {
+      result = backend.hash(alg, data);
+    } catch (e) {
+      return Promise.reject(e);
+    }
+    return Promise.resolve(result);
+  }
+
+  return subtle.digest(name, data).then(function(hash) {
+    return new Buffer(hash);
+  });
+};
+
+if (!subtle.digest)
+  backend.hashAsync = util.promisify(backend.hash);
+
+backend.hash256Async = function hash256Async(data) {
+  return backend.hashAsync('sha256', data).then(function(hash) {
+    return backend.hashAsync('sha256', hash);
+  });
+};
+
+backend.hmacAsync = function _hmacAsync(alg, data, key) {
+  var name = backend.getHash(alg);
+  var use = ['sign'];
+  var algo, promise, result;
+
+  if (!name) {
+    try {
+      result = backend.hmac(alg, data, key);
+    } catch (e) {
+      return Promise.reject(e);
+    }
+    return Promise.resolve(result);
+  }
+
+  algo = {
+    name: 'HMAC',
+    hash: name
+  };
+
+  promise = subtle.importKey('raw', key, algo, true, use);
+
+  return promise.then(function(key) {
+    return subtle.sign('HMAC', key, data);
+  }).then(function(data) {
+    return new Buffer(data);
+  });
+};
+
+if (!subtle.sign)
+  backend.hmacAsync = util.promisify(backend.hmac);
+
+/*
+ * Key Derivation
+ */
+
+backend.pbkdf2 = function pbkdf2(key, salt, iter, len, alg) {
+  var size = backend.hash(alg, new Buffer(0)).length;
+  var blocks = Math.ceil(len / size);
+  var out = new Buffer(len);
+  var buf = new Buffer(salt.length + 4);
+  var block = new Buffer(size);
+  var pos = 0;
+  var i, j, k, mac;
+
+  salt.copy(buf, 0);
+
+  for (i = 0; i < blocks; i++) {
+    buf.writeUInt32BE(i + 1, salt.length, true);
+    mac = backend.hmac(alg, buf, key);
+    mac.copy(block, 0);
+    for (j = 1; j < iter; j++) {
+      mac = backend.hmac(alg, mac, key);
+      for (k = 0; k < size; k++)
+        block[k] ^= mac[k];
+    }
+    block.copy(out, pos);
+    pos += size;
+  }
+
+  return out;
+};
 
 backend.pbkdf2Async = function pbkdf2Async(key, salt, iter, len, alg) {
   var algo = { name: 'PBKDF2' };
   var use = ['deriveBits'];
+  var name = backend.getHash(alg);
   var length = len * 8;
-  var options, promise;
+  var options, promise, result;
+
+  if (!name) {
+    try {
+      result = backend.pbkdf2(key, salt, iter, len, alg);
+    } catch (e) {
+      return Promise.reject(e);
+    }
+    return Promise.resolve(result);
+  }
 
   options = {
     name: 'PBKDF2',
     salt: salt,
     iterations: iter,
-    hash: getHash(alg)
+    hash: name
   };
 
   promise = subtle.importKey('raw', key, algo, false, use);
@@ -66,8 +177,12 @@ backend.pbkdf2Async = function pbkdf2Async(key, salt, iter, len, alg) {
   });
 };
 
-if (!subtle || !subtle.importKey || !subtle.deriveBits)
-  backend.pbkdf2Async = null;
+if (!subtle.deriveBits)
+  backend.pbkdf2Async = util.promisify(backend.pbkdf2);
+
+/*
+ * Ciphers
+ */
 
 backend.encipher = function encipher(data, key, iv) {
   return aes.cbc.encrypt(data, key, iv);
@@ -81,13 +196,53 @@ backend.decipher = function decipher(data, key, iv) {
   }
 };
 
+backend.encipherAsync = function encipherAsync(data, key, iv) {
+  var algo = { name: 'AES-CBC' };
+  var use = ['encrypt'];
+  var options = { name: 'AES-CBC', iv: iv };
+  var promise;
+
+  promise = subtle.importKey('raw', key, algo, false, use);
+
+  return promise.then(function(key) {
+    return subtle.encrypt(options, key, data);
+  }).then(function(result) {
+    return new Buffer(result);
+  });
+};
+
+if (!subtle.encrypt)
+  backend.encipherAsync = util.promisify(backend.encipher);
+
+backend.decipherAsync = function decipherAsync(data, key, iv) {
+  var algo = { name: 'AES-CBC' };
+  var use = ['decrypt'];
+  var options = { name: 'AES-CBC', iv: iv };
+  var promise;
+
+  promise = subtle.importKey('raw', key, algo, false, use);
+
+  return promise.then(function(key) {
+    return subtle.decrypt(options, key, data);
+  }).then(function(result) {
+    return new Buffer(result);
+  });
+};
+
+if (!subtle.decrypt)
+  backend.decipherAsync = util.promisify(backend.decipher);
+
+/*
+ * Misc
+ */
+
 backend.randomBytes = function randomBytes(n) {
   var data = new Uint8Array(n);
   crypto.getRandomValues(data);
   return new Buffer(data.buffer);
 };
 
-if (!crypto || !crypto.getRandomValues) {
+if (!crypto.getRandomValues) {
   // Out of luck here. Use bad randomness for now.
   backend.randomBytes = function randomBytes(n) {
     var data = new Buffer(n);
@@ -100,7 +255,7 @@ if (!crypto || !crypto.getRandomValues) {
   };
 }
 
-function getHash(name) {
+backend.getHash = function getHash(name) {
   switch (name) {
     case 'sha1':
       return 'SHA-1';
@@ -111,6 +266,9 @@ function getHash(name) {
     case 'sha512':
       return 'SHA-512';
     default:
-      throw new Error('Unknown hash.');
+      return null;
   }
-}
+};
+
+backend.crypto = crypto;
+backend.subtle = subtle;
diff --git a/lib/crypto/backend.js b/lib/crypto/backend.js
index ed85d19e..f60b53e8 100644
--- a/lib/crypto/backend.js
+++ b/lib/crypto/backend.js
@@ -7,31 +7,78 @@
 'use strict';
 
 var util = require('../utils/util');
+var co = require('../utils/co');
 var crypto = require('crypto');
+var native = require('../utils/native').binding;
 var backend = exports;
 
+if (!crypto.pbkdf2Sync)
+  throw new Error('This modules requires node.js v0.11.0 or above.');
+
+/*
+ * Hashing
+ */
+
 backend.hash = function hash(alg, data) {
   return crypto.createHash(alg).update(data).digest();
 };
 
-backend.hmac = function hmac(alg, data, salt) {
-  var hmac = crypto.createHmac(alg, salt);
+backend.ripemd160 = function ripemd160(data) {
+  return backend.hash('ripemd160', data);
+};
+
+backend.sha1 = function sha1(data) {
+  return backend.hash('sha1', data);
+};
+
+backend.sha256 = function sha256(data) {
+  return backend.hash('sha256', data);
+};
+
+backend.hash160 = function hash160(data) {
+  return backend.ripemd160(backend.sha256(data));
+};
+
+backend.hash256 = function hash256(data) {
+  return backend.sha256(backend.sha256(data));
+};
+
+backend.hmac = function hmac(alg, data, key) {
+  var hmac = crypto.createHmac(alg, key);
   return hmac.update(data).digest();
 };
 
+if (native) {
+  backend.hash = native.hash;
+  backend.hmac = native.hmac;
+  backend.ripemd160 = native.ripemd160;
+  backend.sha1 = native.sha1;
+  backend.sha256 = native.sha256;
+  backend.hash160 = native.hash160;
+  backend.hash256 = native.hash256;
+}
+
+backend.hashAsync = util.promisify(backend.hash);
+backend.hash256Async = util.promisify(backend.hash256);
+backend.hmacAsync = util.promisify(backend.hmac);
+
+/*
+ * Key Derivation
+ */
+
 backend.pbkdf2 = function pbkdf2(key, salt, iter, len, alg) {
   return crypto.pbkdf2Sync(key, salt, iter, len, alg);
 };
 
-if (!crypto.pbkdf2Sync)
-  backend.pbkdf2 = null;
-
-backend.pbkdf2Async = function pbkdf2Async(key, salt, iter, len, alg, callback) {
-  return crypto.pbkdf2(key, salt, iter, len, alg, callback);
+backend.pbkdf2Async = function pbkdf2Async(key, salt, iter, len, alg) {
+  return new Promise(function(resolve, reject) {
+    crypto.pbkdf2(key, salt, iter, len, alg, co.wrap(resolve, reject));
+  });
 };
 
-if (!crypto.pbkdf2)
-  backend.pbkdf2Async = null;
+/*
+ * Ciphers
+ */
 
 backend.encipher = function encipher(data, key, iv) {
   var cipher = crypto.createCipheriv('aes-256-cbc', key, iv);
@@ -47,4 +94,16 @@ backend.decipher = function decipher(data, key, iv) {
   }
 };
 
+if (native) {
+  backend.encipher = native.encipher;
+  backend.decipher = native.decipher;
+}
+
+backend.encipherAsync = util.promisify(backend.encipher);
+backend.decipherAsync = util.promisify(backend.decipher);
+
+/*
+ * Misc
+ */
+
 backend.randomBytes = crypto.randomBytes;
diff --git a/lib/crypto/crypto.js b/lib/crypto/crypto.js
index 820eb95a..6d7a2917 100644
--- a/lib/crypto/crypto.js
+++ b/lib/crypto/crypto.js
@@ -7,114 +7,111 @@
 
 'use strict';
 
-var assert = require('assert');
+var backend = require('./backend');
+var native = require('../utils/native').binding;
 var scrypt = require('./scrypt');
 var scryptAsync = require('./scrypt-async');
-var co = require('../utils/co');
-var native = require('../utils/native').binding;
-var backend = require('./backend');
 var crypto = exports;
 
 /**
  * Hash with chosen algorithm.
+ * @function
  * @param {String} alg
  * @param {Buffer} data
  * @returns {Buffer}
  */
 
-crypto.hash = function _hash(alg, data) {
-  return backend.hash(alg, data);
-};
+crypto.hash = backend.hash;
 
-if (native)
-  crypto.hash = native.hash;
+/**
+ * Hash with chosen algorithm (async).
+ * @function
+ * @param {String} alg
+ * @param {Buffer} data
+ * @returns {Buffer}
+ */
+
+crypto.hashAsync = backend.hashAsync;
 
 /**
  * Hash with ripemd160.
+ * @function
  * @param {Buffer} data
  * @returns {Buffer}
  */
 
-crypto.ripemd160 = function ripemd160(data) {
-  return crypto.hash('ripemd160', data);
-};
+crypto.ripemd160 = backend.ripemd160;
 
 /**
  * Hash with sha1.
+ * @function
  * @param {Buffer} data
  * @returns {Buffer}
  */
 
-crypto.sha1 = function sha1(data) {
-  return crypto.hash('sha1', data);
-};
+crypto.sha1 = backend.sha1;
 
 /**
  * Hash with sha256.
+ * @function
  * @param {Buffer} data
  * @returns {Buffer}
  */
 
-crypto.sha256 = function sha256(data) {
-  return crypto.hash('sha256', data);
-};
-
-if (native)
-  crypto.sha256 = native.sha256;
+crypto.sha256 = backend.sha256;
 
 /**
  * Hash with sha256 and ripemd160 (OP_HASH160).
+ * @function
  * @param {Buffer} data
  * @returns {Buffer}
  */
 
-crypto.hash160 = function hash160(data) {
-  return crypto.ripemd160(crypto.sha256(data));
-};
-
-if (native)
-  crypto.hash160 = native.hash160;
+crypto.hash160 = backend.hash160;
 
 /**
  * Hash with sha256 twice (OP_HASH256).
+ * @function
  * @param {Buffer} data
  * @returns {Buffer}
  */
 
-crypto.hash256 = function hash256(data) {
-  return crypto.sha256(crypto.sha256(data));
-};
-
-if (native)
-  crypto.hash256 = native.hash256;
+crypto.hash256 = backend.hash256;
 
 /**
- * Create a sha256 checksum (common in bitcoin).
+ * Hash with sha256 twice (async).
+ * @function
  * @param {Buffer} data
  * @returns {Buffer}
  */
 
-crypto.checksum = function checksum(data) {
-  return crypto.hash256(data).slice(0, 4);
-};
+crypto.hash256Async = backend.hash256Async;
 
 /**
  * Create an HMAC.
+ * @function
  * @param {String} alg
  * @param {Buffer} data
- * @param {Buffer} salt
+ * @param {Buffer} key
  * @returns {Buffer} HMAC
  */
 
-crypto.hmac = function hmac(alg, data, salt) {
-  return backend.hmac(alg, data, salt);
-};
+crypto.hmac = backend.hmac;
 
-if (native)
-  crypto.hmac = native.hmac;
+/**
+ * Create an HMAC (async).
+ * @function
+ * @param {String} alg
+ * @param {Buffer} data
+ * @param {Buffer} key
+ * @returns {Buffer} HMAC
+ */
+
+crypto.hmacAsync = backend.hmacAsync;
 
 /**
  * Perform key derivation using PBKDF2.
+ * @function
  * @param {Buffer} key
  * @param {Buffer} salt
  * @param {Number} iter
@@ -123,21 +120,11 @@ if (native)
  * @returns {Buffer}
  */
 
-crypto.pbkdf2 = function pbkdf2(key, salt, iter, len, alg) {
-  if (typeof key === 'string')
-    key = new Buffer(key, 'utf8');
-
-  if (typeof salt === 'string')
-    salt = new Buffer(salt, 'utf8');
-
-  if (backend.pbkdf2)
-    return backend.pbkdf2(key, salt, iter, len, alg);
-
-  return crypto._pbkdf2(key, salt, iter, len, alg);
-};
+crypto.pbkdf2 = backend.pbkdf2;
 
 /**
  * Execute pbkdf2 asynchronously.
+ * @function
  * @param {Buffer} key
  * @param {Buffer} salt
  * @param {Number} iter
@@ -146,32 +133,11 @@ crypto.pbkdf2 = function pbkdf2(key, salt, iter, len, alg) {
  * @returns {Promise}
  */
 
-crypto.pbkdf2Async = function pbkdf2Async(key, salt, iter, len, alg) {
-  var result;
-
-  if (typeof key === 'string')
-    key = new Buffer(key, 'utf8');
-
-  if (typeof salt === 'string')
-    salt = new Buffer(salt, 'utf8');
-
-  if (backend.pbkdf2Async) {
-    return new Promise(function(resolve, reject) {
-      backend.pbkdf2Async(key, salt, iter, len, alg, co.wrap(resolve, reject));
-    });
-  }
-
-  try {
-    result = crypto._pbkdf2(key, salt, iter, len, alg);
-  } catch (e) {
-    return Promise.reject(e);
-  }
-
-  return Promise.resolve(result);
-};
+crypto.pbkdf2Async = backend.pbkdf2Async;
 
 /**
  * Perform key derivation using scrypt.
+ * @function
  * @param {Buffer} passwd
  * @param {Buffer} salt
  * @param {Number} N
@@ -181,18 +147,11 @@ crypto.pbkdf2Async = function pbkdf2Async(key, salt, iter, len, alg) {
  * @returns {Buffer}
  */
 
-crypto.scrypt = function _scrypt(passwd, salt, N, r, p, len) {
-  if (typeof passwd === 'string')
-    passwd = new Buffer(passwd, 'utf8');
-
-  if (typeof salt === 'string')
-    salt = new Buffer(salt, 'utf8');
-
-  return scrypt(passwd, salt, N, r, p, len);
-};
+crypto.scrypt = scrypt;
 
 /**
  * Execute scrypt asynchronously.
+ * @function
  * @param {Buffer} passwd
  * @param {Buffer} salt
  * @param {Number} N
@@ -202,66 +161,18 @@ crypto.scrypt = function _scrypt(passwd, salt, N, r, p, len) {
  * @returns {Promise}
  */
 
-crypto.scryptAsync = function _scrypt(passwd, salt, N, r, p, len) {
-  if (typeof passwd === 'string')
-    passwd = new Buffer(passwd, 'utf8');
-
-  if (typeof salt === 'string')
-    salt = new Buffer(salt, 'utf8');
-
-  return new Promise(function(resolve, reject) {
-    scryptAsync(passwd, salt, N, r, p, len, co.wrap(resolve, reject));
-  });
-};
-
-/**
- * Perform key derivation using PBKDF2.
- * @private
- * @param {Buffer} key
- * @param {Buffer} salt
- * @param {Number} iter
- * @param {Number} len
- * @param {String} alg
- * @returns {Buffer}
- */
-
-crypto._pbkdf2 = function pbkdf2(key, salt, iter, len, alg) {
-  var size = crypto.hash(alg, new Buffer(0)).length;
-  var blocks = Math.ceil(len / size);
-  var out = new Buffer(len);
-  var buf = new Buffer(salt.length + 4);
-  var block = new Buffer(size);
-  var pos = 0;
-  var i, j, k, mac;
-
-  salt.copy(buf, 0);
-
-  for (i = 0; i < blocks; i++) {
-    buf.writeUInt32BE(i + 1, salt.length, true);
-    mac = crypto.hmac(alg, buf, key);
-    mac.copy(block, 0);
-    for (j = 1; j < iter; j++) {
-      mac = crypto.hmac(alg, mac, key);
-      for (k = 0; k < size; k++)
-        block[k] ^= mac[k];
-    }
-    block.copy(out, pos);
-    pos += size;
-  }
-
-  return out;
-};
+crypto.scryptAsync = scryptAsync;
 
 /**
  * Perform hkdf extraction.
  * @param {Buffer} ikm
- * @param {Buffer} salt
+ * @param {Buffer} key
  * @param {String} alg
  * @returns {Buffer}
  */
 
-crypto.hkdfExtract = function hkdfExtract(ikm, salt, alg) {
-  return crypto.hmac(alg, ikm, salt);
+crypto.hkdfExtract = function hkdfExtract(ikm, key, alg) {
+  return crypto.hmac(alg, ikm, key);
 };
 
 /**
@@ -424,38 +335,47 @@ if (native)
 
 /**
  * Encrypt with aes-256-cbc.
+ * @function
  * @param {Buffer} data
  * @param {Buffer} key - 256 bit key.
  * @param {Buffer} iv - 128 bit initialization vector.
  * @returns {Buffer}
  */
 
-crypto.encipher = function encipher(data, key, iv) {
-  assert(Buffer.isBuffer(data));
-  assert(Buffer.isBuffer(key));
-  assert(Buffer.isBuffer(iv));
-  assert(key.length === 32);
-  assert(iv.length === 16);
+crypto.encipher = backend.encipher;
 
-  return backend.encipher(data, key, iv);
-};
+/**
+ * Encrypt with aes-256-cbc (async).
+ * @function
+ * @param {Buffer} data
+ * @param {Buffer} key - 256 bit key.
+ * @param {Buffer} iv - 128 bit initialization vector.
+ * @returns {Promise}
+ */
+
+crypto.encipherAsync = backend.encipherAsync;
 
 /**
  * Decrypt with aes-256-cbc.
+ * @function
  * @param {Buffer} data
  * @param {Buffer} key - 256 bit key.
  * @param {Buffer} iv - 128 bit initialization vector.
  * @returns {Buffer}
  */
 
-crypto.decipher = function decipher(data, key, iv) {
-  assert(Buffer.isBuffer(data));
-  assert(Buffer.isBuffer(key));
-  assert(Buffer.isBuffer(iv));
-  assert(key.length === 32);
-  assert(iv.length === 16);
-  return backend.decipher(data, key, iv);
-};
+crypto.decipher = backend.decipher;
+
+/**
+ * Decrypt with aes-256-cbc (async).
+ * @function
+ * @param {Buffer} data
+ * @param {Buffer} key - 256 bit key.
+ * @param {Buffer} iv - 128 bit initialization vector.
+ * @returns {Promise}
+ */
+
+crypto.decipherAsync = backend.decipherAsync;
 
 /**
  * memcmp in constant time (can only return true or false).
@@ -488,21 +408,6 @@ crypto.ccmp = function ccmp(a, b) {
   return res === 0;
 };
 
-/**
- * Compare two bytes in constant time.
- * @param {Number} a
- * @param {Number} b
- * @returns {Boolean}
- */
-
-crypto.ceq = function ceq(a, b) {
-  var r = ~(a ^ b) & 0xff;
-  r &= r >>> 4;
-  r &= r >>> 2;
-  r &= r >>> 1;
-  return r === 1;
-};
-
 /**
  * A maybe-secure memzero.
  * @param {Buffer} data
diff --git a/lib/crypto/ec-secp256k1.js b/lib/crypto/ec-secp256k1.js
index dbbd9ba3..afa68913 100644
--- a/lib/crypto/ec-secp256k1.js
+++ b/lib/crypto/ec-secp256k1.js
@@ -9,7 +9,7 @@
 
 var assert = require('assert');
 var util = require('../utils/util');
-var crypto = require('./crypto');
+var backend = require('./backend');
 var secp256k1 = require('secp256k1');
 
 /*
@@ -40,7 +40,7 @@ ec.generatePrivateKey = function generatePrivateKey() {
   var priv;
 
   do {
-    priv = crypto.randomBytes(32);
+    priv = backend.randomBytes(32);
   } while (!secp256k1.privateKeyVerify(priv));
 
   return priv;
diff --git a/lib/crypto/index.js b/lib/crypto/index.js
index 64b30b43..952f4dae 100644
--- a/lib/crypto/index.js
+++ b/lib/crypto/index.js
@@ -4,13 +4,15 @@ var crypto = require('./crypto');
 
 exports.crypto = crypto;
 exports.hash = crypto.hash;
+exports.hashAsync = crypto.hashAsync;
 exports.ripemd160 = crypto.ripemd160;
 exports.sha1 = crypto.sha1;
 exports.sha256 = crypto.sha256;
 exports.hash160 = crypto.hash160;
 exports.hash256 = crypto.hash256;
-exports.checksum = crypto.checksum;
+exports.hash256Async = crypto.hash256Async;
 exports.hmac = crypto.hmac;
+exports.hmacAsync = crypto.hmacAsync;
 exports.pbkdf2 = crypto.pbkdf2;
 exports.pbkdf2Async = crypto.pbkdf2Async;
 exports.scrypt = crypto.scrypt;
@@ -24,7 +26,6 @@ exports.checkMerkleBranch = crypto.checkMerkleBranch;
 exports.encipher = crypto.encipher;
 exports.decipher = crypto.decipher;
 exports.ccmp = crypto.ccmp;
-exports.ceq = crypto.ceq;
 exports.cleanse = crypto.cleanse;
 exports.randomBytes = crypto.randomBytes;
 exports.randomInt = crypto.randomInt;
diff --git a/lib/crypto/pk-browser.js b/lib/crypto/pk-browser.js
index 02f7b080..b42a1308 100644
--- a/lib/crypto/pk-browser.js
+++ b/lib/crypto/pk-browser.js
@@ -9,8 +9,11 @@
 var assert = require('assert');
 var BN = require('bn.js');
 var ASN1 = require('../utils/asn1');
+var util = require('../utils/util');
+var co = require('../utils/co');
 var elliptic = require('elliptic');
-var crypto = require('./crypto');
+var backend = require('./backend');
+var subtle = backend.subtle;
 var dsa, rsa, ecdsa;
 
 /*
@@ -23,10 +26,14 @@ dsa.verify = function verify(alg, msg, sig, key, params) {
   throw new Error('DSA not implemented.');
 };
 
+dsa.verifyAsync = util.promisify(dsa.verify);
+
 dsa.sign = function sign(alg, msg, key, params) {
   throw new Error('DSA not implemented.');
 };
 
+dsa.signAsync = util.promisify(dsa.sign);
+
 /*
  * RSA
  */
@@ -52,7 +59,7 @@ rsa.verify = function verify(alg, msg, sig, key) {
   if (!prefix)
     throw new Error('Unknown PKCS prefix.');
 
-  hash = crypto.hash(alg, msg);
+  hash = backend.hash(alg, msg);
   len = prefix.length + hash.length;
   pub = ASN1.parseRSAPublic(key);
 
@@ -66,14 +73,14 @@ rsa.verify = function verify(alg, msg, sig, key) {
   m = rsa.encrypt(N, e, sig);
   em = leftpad(m, k);
 
-  ok = crypto.ceq(em[0], 0x00);
-  ok &= crypto.ceq(em[1], 0x01);
-  ok &= crypto.ccmp(em.slice(k - hash.length, k), hash);
-  ok &= crypto.ccmp(em.slice(k - len, k - hash.length), prefix);
-  ok &= crypto.ceq(em[k - len - 1], 0x00);
+  ok = ceq(em[0], 0x00);
+  ok &= ceq(em[1], 0x01);
+  ok &= backend.ccmp(em.slice(k - hash.length, k), hash);
+  ok &= backend.ccmp(em.slice(k - len, k - hash.length), prefix);
+  ok &= ceq(em[k - len - 1], 0x00);
 
   for (i = 2; i < k - len - 1; i++)
-    ok &= crypto.ceq(em[i], 0xff);
+    ok &= ceq(em[i], 0xff);
 
   return ok === 1;
 };
@@ -86,7 +93,7 @@ rsa.sign = function sign(alg, msg, key) {
   if (!prefix)
     throw new Error('Unknown PKCS prefix.');
 
-  hash = crypto.hash(alg, msg);
+  hash = backend.hash(alg, msg);
   len = prefix.length + hash.length;
   priv = ASN1.parseRSAPrivate(key);
 
@@ -110,6 +117,82 @@ rsa.sign = function sign(alg, msg, key) {
   return rsa.decrypt(N, D, em);
 };
 
+rsa.verifyAsync = co(function* verifyAsync(alg, msg, sig, key) {
+  var use = ['verify'];
+  var name = backend.getHash(alg);
+  var pub, data, algo, ckey;
+
+  if (!name)
+    return rsa.verify(alg, msg, sig, key);
+
+  pub = ASN1.parseRSAPublic(key);
+
+  data = {
+    kty: 'RSA',
+    n: toBase64(pub.modulus),
+    e: toBase64(pub.publicExponent),
+    alg: 'RS256',
+    ext: true
+  };
+
+  algo = {
+    name: 'RSASSA-PKCS1-v1_5',
+    hash: { name: name }
+  };
+
+  ckey = yield subtle.importKey('jwk', data, algo, false, use);
+
+  algo = {
+    name: 'RSASSA-PKCS1-v1_5',
+  };
+
+  return yield subtle.verify(algo, ckey, sig, msg);
+});
+
+if (!subtle.verify)
+  rsa.verifyAsync = util.promisify(rsa.verify);
+
+rsa.signAsync = co(function* signAsync(alg, msg, key) {
+  var use = ['sign'];
+  var name = backend.getHash(alg);
+  var pub, data, algo, ckey;
+
+  if (!name)
+    return rsa.sign(alg, msg, key);
+
+  pub = ASN1.parseRSAPrivate(key);
+
+  data = {
+    kty: 'RSA',
+    n: toBase64(pub.modulus),
+    e: toBase64(pub.publicExponent),
+    d: toBase64(pub.privateExponent),
+    p: toBase64(pub.prime1),
+    q: toBase64(pub.prime2),
+    dp: toBase64(pub.exponent1),
+    dq: toBase64(pub.exponent2),
+    qi: toBase64(pub.coefficient),
+    alg: 'RS256',
+    ext: true
+  };
+
+  algo = {
+    name: 'RSASSA-PKCS1-v1_5',
+    hash: { name: name }
+  };
+
+  ckey = yield subtle.importKey('jwk', data, algo, false, use);
+
+  algo = {
+    name: 'RSASSA-PKCS1-v1_5',
+  };
+
+  return yield subtle.sign(algo, ckey, msg);
+});
+
+if (!subtle.sign)
+  rsa.signAsync = util.promisify(rsa.sign);
+
 rsa.decrypt = function decrypt(N, D, m) {
   var c = new BN(m);
 
@@ -137,28 +220,91 @@ rsa.encrypt = function encrypt(N, e, m) {
 
 ecdsa = {};
 
-ecdsa.verify = function verify(curve, msg, alg, key, sig) {
+ecdsa.verify = function verify(curve, alg, msg, key, sig) {
   var ec, hash;
 
   assert(curve, 'No curve selected.');
 
   ec = elliptic.ec(curve);
-  hash = crypto.hash(alg, msg);
+  hash = backend.hash(alg, msg);
 
   return ec.verify(hash, sig, key);
 };
 
-ecdsa.sign = function sign(curve, msg, alg, key) {
+ecdsa.sign = function sign(curve, alg, msg, key) {
   var ec, hash;
 
   assert(curve, 'No curve selected.');
 
   ec = elliptic.ec(curve);
-  hash = crypto.hash(alg, msg);
+  hash = backend.hash(alg, msg);
 
   return new Buffer(ec.sign(hash, key));
 };
 
+ecdsa.verifyAsync = co(function* verifyAsync(curve, alg, msg, sig, key) {
+  var use = ['verify'];
+  var name = backend.getHash(alg);
+  var curveName = getCurve(curve);
+  var pub, data, algo, ckey;
+
+  if (!name || !curveName)
+    return ecdsa.verify(curve, alg, msg, sig, key);
+
+  pub = parseECPublic(key, curve);
+
+  data = {
+    kty: 'EC',
+    x: toBase64(pub.x),
+    y: toBase64(pub.y),
+    ext: true
+  };
+
+  algo = {
+    name: 'ECDSA',
+    namedCurve: curveName
+  };
+
+  ckey = yield subtle.importKey('jwk', data, algo, false, use);
+
+  algo = {
+    name: 'ECDSA',
+    hash: name
+  };
+
+  return yield subtle.verify(algo, ckey, sig, msg);
+});
+
+if (!subtle.verify)
+  ecdsa.verifyAsync = util.promisify(ecdsa.verify);
+
+ecdsa.signAsync = co(function* signAsync(curve, alg, msg, key) {
+  var use = ['sign'];
+  var name = backend.getHash(alg);
+  var curveName = getCurve(curve);
+  var algo, ckey;
+
+  if (!name || !curveName)
+    return ecdsa.sign(curve, alg, msg, key);
+
+  algo = {
+    name: 'ECDSA',
+    namedCurve: curveName
+  };
+
+  ckey = yield subtle.importKey('raw', key, algo, false, use);
+
+  algo = {
+    name: 'ECDSA',
+    hash: name
+  };
+
+  return yield subtle.sign(algo, ckey, msg);
+});
+
+if (!subtle.sign)
+  ecdsa.signAsync = util.promisify(ecdsa.sign);
+
 /*
  * Helpers
  */
@@ -178,6 +324,44 @@ function leftpad(input, size) {
   return out;
 }
 
+function toBase64(data) {
+  var str = data.toString('base64');
+  str = str.replace(/\+/g, '-');
+  str = str.replace(/\//g, '_');
+  str = str.replace(/=+$/, '');
+  return str;
+}
+
+function getCurve(name) {
+  switch (name) {
+    case 'p256':
+      return 'P-256';
+    case 'p384':
+      return 'P-384';
+    case 'p521':
+      return 'P-521';
+    default:
+      return null;
+  }
+}
+
+function parseECPublic(data, curve) {
+  var ec = elliptic.ec(curve).curve;
+  var point = ec.decodePoint(data);
+  return {
+    x: point.toArrayLike(Buffer, 'be', 32),
+    y: point.toArrayLike(Buffer, 'be', 32)
+  };
+}
+
+function ceq(a, b) {
+  var r = ~(a ^ b) & 0xff;
+  r &= r >>> 4;
+  r &= r >>> 2;
+  r &= r >>> 1;
+  return r === 1;
+}
+
 /*
  * Expose
  */
diff --git a/lib/crypto/pk.js b/lib/crypto/pk.js
index 4decbd7b..08171e42 100644
--- a/lib/crypto/pk.js
+++ b/lib/crypto/pk.js
@@ -9,7 +9,8 @@
 var assert = require('assert');
 var PEM = require('../utils/pem');
 var elliptic = require('elliptic');
-var crypto = require('./crypto');
+var util = require('../utils/util');
+var backend = require('./backend');
 var nodeCrypto = require('crypto');
 var dsa, rsa, ecdsa;
 
@@ -29,6 +30,9 @@ dsa.sign = function _sign(alg, msg, key, params) {
   return sign('dsa', alg, msg, pem);
 };
 
+dsa.verifyAsync = util.promisify(dsa.verify);
+dsa.signAsync = util.promisify(dsa.sign);
+
 /*
  * RSA
  */
@@ -45,6 +49,9 @@ rsa.sign = function _sign(alg, msg, key) {
   return sign('rsa', alg, msg, pem);
 };
 
+rsa.verifyAsync = util.promisify(rsa.verify);
+rsa.signAsync = util.promisify(rsa.sign);
+
 /*
  * ECDSA
  */
@@ -57,7 +64,7 @@ ecdsa.verify = function verify(curve, msg, alg, key, sig) {
   assert(curve, 'No curve selected.');
 
   ec = elliptic.ec(curve);
-  hash = crypto.hash(alg, msg);
+  hash = backend.hash(alg, msg);
 
   return ec.verify(hash, sig, key);
 };
@@ -68,11 +75,14 @@ ecdsa.sign = function sign(curve, msg, alg, key) {
   assert(curve, 'No curve selected.');
 
   ec = elliptic.ec(curve);
-  hash = crypto.hash(alg, msg);
+  hash = backend.hash(alg, msg);
 
   return new Buffer(ec.sign(hash, key));
 };
 
+ecdsa.verifyAsync = util.promisify(ecdsa.verify);
+ecdsa.signAsync = util.promisify(ecdsa.sign);
+
 /*
  * Helpers
  */
diff --git a/lib/crypto/schnorr.js b/lib/crypto/schnorr.js
index 11e6485c..80b80208 100644
--- a/lib/crypto/schnorr.js
+++ b/lib/crypto/schnorr.js
@@ -10,7 +10,7 @@ var BN = require('bn.js');
 var elliptic = require('elliptic');
 var Signature = require('elliptic/lib/elliptic/ec/signature');
 var hmacDRBG = require('elliptic/lib/elliptic/hmac-drbg');
-var sha256 = require('./crypto').sha256;
+var sha256 = require('./backend').sha256;
 var secp256k1 = elliptic.ec('secp256k1');
 var curve = secp256k1.curve;
 var curves = elliptic.curves;
diff --git a/lib/crypto/scrypt-async.js b/lib/crypto/scrypt-async.js
index eb0fe710..54a5342f 100644
--- a/lib/crypto/scrypt-async.js
+++ b/lib/crypto/scrypt-async.js
@@ -33,10 +33,11 @@
 
 'use strict';
 
-var util = require('../utils/util');
-var crypto = require('./crypto');
+var co = require('../utils/co');
+var backend = require('./backend');
 var native = require('../utils/native').binding;
 var U32Array = typeof Uint32Array === 'function' ? Uint32Array : Array;
+var scryptAsync, smix;
 
 /**
  * Javascript scrypt implementation. Scrypt is
@@ -51,35 +52,28 @@ var U32Array = typeof Uint32Array === 'function' ? Uint32Array : Array;
  * @returns {Buffer}
  */
 
-function scryptAsync(passwd, salt, N, r, p, len, callback) {
-  var V, XY;
+scryptAsync = co(function* scryptAsync(passwd, salt, N, r, p, len) {
+  var i, B, V, XY;
 
   if (r * p >= (1 << 30))
-    return callback(new Error('EFBIG'));
+    throw new Error('EFBIG');
 
   if ((N & (N - 1)) !== 0 || N === 0)
-    return callback(new Error('EINVAL'));
+    throw new Error('EINVAL');
 
   if (N > 0xffffffff)
-    return callback(new Error('EINVAL'));
+    throw new Error('EINVAL');
 
   XY = new Buffer(256 * r);
   V = new Buffer(128 * r * N);
 
-  crypto.pbkdf2Async(passwd, salt, 1, p * 128 * r, 'sha256', function(err, B) {
-    if (err)
-      return callback(err);
+  B = yield backend.pbkdf2Async(passwd, salt, 1, p * 128 * r, 'sha256');
 
-    forRangeSerial(0, p, function(i, next) {
-      smix(B, i * 128 * r, r, N, V, XY, next);
-    }, function(err) {
-      if (err)
-        return callback(err);
+  for (i = 0; i < p; i++)
+    yield smix(B, i * 128 * r, r, N, V, XY);
 
-      crypto.pbkdf2Async(passwd, B, 1, len, 'sha256', callback);
-    });
-  });
-}
+  return yield backend.pbkdf2Async(passwd, B, 1, len, 'sha256');
+});
 
 if (native)
   scryptAsync = native.scryptAsync;
@@ -148,7 +142,7 @@ function R(a, b) {
   return (a << b) | (a >>> (32 - b));
 }
 
-function blockmix_salsa8(B, Y, Yo, r, callback) {
+function blockmix_salsa8(B, Y, Yo, r) {
   var X = new Buffer(64);
   var i;
 
@@ -165,42 +159,35 @@ function blockmix_salsa8(B, Y, Yo, r, callback) {
 
   for (i = 0; i < r; i++)
     blkcpy(B, Y, (i + r) * 64, Yo + (i * 2 + 1) * 64, 64);
-
-  util.nextTick(callback);
 }
 
 function integerify(B, r) {
   return B.readUInt32LE((2 * r - 1) * 64, true);
 }
 
-function smix(B, Bo, r, N, V, XY, callback) {
+smix = co(function* smix(B, Bo, r, N, V, XY) {
   var X = XY;
   var Y = XY;
+  var i;
   var j;
 
   blkcpy(X, B, 0, Bo, 128 * r);
 
-  forRangeSerial(0, N, function(i, next) {
+  for (i = 0; i < N; i++) {
     blkcpy(V, X, i * (128 * r), 0, 128 * r);
-    blockmix_salsa8(X, Y, 128 * r, r, next);
-  }, function(err) {
-    if (err)
-      return callback(err);
+    blockmix_salsa8(X, Y, 128 * r, r);
+    yield co.wait();
+  }
 
-    forRangeSerial(0, N, function(i, next) {
-      j = integerify(X, r) & (N - 1);
-      blkxor(X, V, 0, j * (128 * r), 128 * r);
-      blockmix_salsa8(X, Y, 128 * r, r, next);
-    }, function(err) {
-      if (err)
-        return callback(err);
+  for (i = 0; i < N; i++) {
+    j = integerify(X, r) & (N - 1);
+    blkxor(X, V, 0, j * (128 * r), 128 * r);
+    blockmix_salsa8(X, Y, 128 * r, r);
+    yield co.wait();
+  }
 
-      blkcpy(B, X, Bo, 0, 128 * r);
-
-      callback();
-    });
-  });
-}
+  blkcpy(B, X, Bo, 0, 128 * r);
+});
 
 function blkcpy(dest, src, s1, s2, len) {
   src.copy(dest, s1, s2, s2 + len);
@@ -211,17 +198,6 @@ function blkxor(dest, src, s1, s2, len) {
     dest[s1 + i] ^= src[s2 + i];
 }
 
-function forRangeSerial(from, to, iter, callback) {
-  (function next(err) {
-    if (err)
-      return callback(err);
-    if (from >= to)
-      return callback();
-    from++;
-    iter(from - 1, next, from - 1);
-  })();
-}
-
 /*
  * Expose
  */
diff --git a/lib/crypto/scrypt.js b/lib/crypto/scrypt.js
index d4163185..6c306cad 100644
--- a/lib/crypto/scrypt.js
+++ b/lib/crypto/scrypt.js
@@ -33,7 +33,7 @@
 
 'use strict';
 
-var crypto = require('./crypto');
+var backend = require('./backend');
 var native = require('../utils/native').binding;
 var U32Array = typeof Uint32Array === 'function' ? Uint32Array : Array;
 
@@ -65,12 +65,12 @@ function scrypt(passwd, salt, N, r, p, len) {
   XY = new Buffer(256 * r);
   V = new Buffer(128 * r * N);
 
-  B = crypto.pbkdf2(passwd, salt, 1, p * 128 * r, 'sha256');
+  B = backend.pbkdf2(passwd, salt, 1, p * 128 * r, 'sha256');
 
   for (i = 0; i < p; i++)
     smix(B, i * 128 * r, r, N, V, XY);
 
-  return crypto.pbkdf2(passwd, B, 1, len, 'sha256');
+  return backend.pbkdf2(passwd, B, 1, len, 'sha256');
 }
 
 if (native)
diff --git a/lib/hd/mnemonic.js b/lib/hd/mnemonic.js
index bca0532e..88c982d4 100644
--- a/lib/hd/mnemonic.js
+++ b/lib/hd/mnemonic.js
@@ -135,14 +135,19 @@ Mnemonic.prototype.destroy = function destroy() {
  */
 
 Mnemonic.prototype.toSeed = function toSeed(passphrase) {
+  var phrase, passwd;
+
   if (!passphrase)
     passphrase = this.passphrase;
 
   this.passphrase = passphrase;
 
+  phrase = nfkd(this.getPhrase());
+  passwd = nfkd('mnemonic' + passphrase);
+
   return crypto.pbkdf2(
-    nfkd(this.getPhrase()),
-    nfkd('mnemonic' + passphrase),
+    new Buffer(phrase, 'utf8'),
+    new Buffer(passwd, 'utf8'),
     2048, 64, 'sha512');
 };
 
diff --git a/lib/net/bip152.js b/lib/net/bip152.js
index 6ceeb13e..f4a90db2 100644
--- a/lib/net/bip152.js
+++ b/lib/net/bip152.js
@@ -349,7 +349,7 @@ CompactBlock.prototype.fromBlock = function fromBlock(block, witness, nonce) {
   this.totalTX = block.totalTX;
 
   if (!nonce)
-    nonce = util.nonce(true);
+    nonce = util.nonce();
 
   this.keyNonce = nonce;
 
diff --git a/lib/net/packets.js b/lib/net/packets.js
index 04398fa9..23adad87 100644
--- a/lib/net/packets.js
+++ b/lib/net/packets.js
@@ -7,7 +7,6 @@
 
 'use strict';
 
-var BN = require('bn.js');
 var constants = require('../protocol/constants');
 var util = require('../utils/util');
 var assert = require('assert');
@@ -122,7 +121,7 @@ function VersionPacket(options) {
   this.ts = time.now();
   this.recv = new NetworkAddress();
   this.from = new NetworkAddress();
-  this.nonce = new BN(0);
+  this.nonce = constants.ZERO_U64;
   this.agent = constants.USER_AGENT;
   this.height = 0;
   this.relay = true;
@@ -196,7 +195,7 @@ VersionPacket.prototype.toRaw = function toRaw(writer) {
   p.write64(this.ts);
   this.recv.toRaw(false, p);
   this.from.toRaw(false, p);
-  p.writeU64(this.nonce);
+  p.writeBytes(this.nonce);
   p.writeVarString(this.agent, 'ascii');
   p.write32(this.height);
   p.writeU8(this.relay ? 1 : 0);
@@ -278,7 +277,7 @@ VersionPacket.prototype.fromRaw = function fromRaw(data) {
 
   if (p.left() > 0) {
     this.from.fromRaw(p, false);
-    this.nonce = p.readU64();
+    this.nonce = p.readBytes(8);
   }
 
   if (p.left() > 0)
@@ -392,7 +391,7 @@ PingPacket.prototype.toRaw = function toRaw(writer) {
   var p = BufferWriter(writer);
 
   if (this.nonce)
-    p.writeU64(this.nonce);
+    p.writeBytes(this.nonce);
 
   if (!writer)
     p = p.render();
@@ -409,7 +408,7 @@ PingPacket.prototype.toRaw = function toRaw(writer) {
 PingPacket.prototype.fromRaw = function fromRaw(data) {
   var p = BufferReader(data);
   if (p.left() >= 8)
-    this.nonce = p.readU64();
+    this.nonce = p.readBytes(8);
   return this;
 };
 
@@ -440,7 +439,7 @@ function PongPacket(nonce) {
 
   Packet.call(this);
 
-  this.nonce = nonce || new BN(0);
+  this.nonce = nonce || constants.ZERO_U64;
 }
 
 util.inherits(PongPacket, Packet);
@@ -456,7 +455,7 @@ PongPacket.prototype.type = exports.types.PONG;
 PongPacket.prototype.toRaw = function toRaw(writer) {
   var p = BufferWriter(writer);
 
-  p.writeU64(this.nonce);
+  p.writeBytes(this.nonce);
 
   if (!writer)
     p = p.render();
@@ -472,7 +471,7 @@ PongPacket.prototype.toRaw = function toRaw(writer) {
 
 PongPacket.prototype.fromRaw = function fromRaw(data) {
   var p = BufferReader(data);
-  this.nonce = p.readU64();
+  this.nonce = p.readBytes(8);
   return this;
 };
 
diff --git a/lib/net/peer.js b/lib/net/peer.js
index 62f60cf8..2dee24e1 100644
--- a/lib/net/peer.js
+++ b/lib/net/peer.js
@@ -1439,7 +1439,7 @@ Peer.prototype._handleVersion = co(function* _handleVersion(version) {
     throw new Error('Peer sent a duplicate version.');
 
   if (!this.network.selfConnect) {
-    if (version.nonce.cmp(this.pool.localNonce) === 0) {
+    if (util.equal(version.nonce, this.pool.localNonce)) {
       this.ignore();
       throw new Error('We connected to ourself. Oops.');
     }
@@ -1869,8 +1869,8 @@ Peer.prototype._handlePong = function _handlePong(packet) {
     return;
   }
 
-  if (nonce.cmp(this.challenge) !== 0) {
-    if (nonce.cmpn(0) === 0) {
+  if (!util.equal(nonce, this.challenge)) {
+    if (util.equal(nonce, constants.ZERO_U64)) {
       this.logger.debug('Peer sent a zero nonce (%s).', this.hostname);
       this.challenge = null;
       return;
diff --git a/lib/net/pool.js b/lib/net/pool.js
index 03f77bd3..9d63359e 100644
--- a/lib/net/pool.js
+++ b/lib/net/pool.js
@@ -917,6 +917,9 @@ Pool.prototype._handleBlock = co(function* _handleBlock(block, peer) {
   // Fulfill the load request.
   requested = this.fulfill(block);
 
+  if (util.isBrowser)
+    yield block.hashAsync();
+
   // Someone is sending us blocks without
   // us requesting them.
   if (!requested) {
@@ -1330,6 +1333,9 @@ Pool.prototype.hasReject = function hasReject(hash) {
 Pool.prototype._handleTX = co(function* _handleTX(tx, peer) {
   var i, requested, missing;
 
+  if (util.isBrowser)
+    yield tx.hashAsync();
+
   // Fulfill the load request.
   requested = this.fulfill(tx);
 
diff --git a/lib/primitives/abstractblock.js b/lib/primitives/abstractblock.js
index e7044890..82f28e7d 100644
--- a/lib/primitives/abstractblock.js
+++ b/lib/primitives/abstractblock.js
@@ -10,6 +10,7 @@
 var assert = require('assert');
 var constants = require('../protocol/constants');
 var util = require('../utils/util');
+var co = require('../utils/co');
 var crypto = require('../crypto/crypto');
 var btcutils = require('../btc/utils');
 var VerifyResult = require('../btc/errors').VerifyResult;
@@ -160,6 +161,54 @@ AbstractBlock.prototype.hash = function hash(enc) {
   return hash;
 };
 
+/**
+ * Hash the block headers (async).
+ * @param {String?} enc - Can be `'hex'` or `null`.
+ * @returns {Hash|Buffer} hash
+ */
+
+AbstractBlock.prototype.hashAsync = co(function* hashAsync(enc) {
+  var hash = this._hash;
+  var hex;
+
+  if (!hash) {
+    hash = yield crypto.hash256Async(this.abbr());
+    if (!this.mutable)
+      this._hash = hash;
+  }
+
+  if (enc === 'hex') {
+    hex = this._hhash;
+    if (!hex) {
+      hex = hash.toString('hex');
+      if (!this.mutable)
+        this._hhash = hex;
+    }
+    hash = hex;
+  }
+
+  return hash;
+});
+
+/**
+ * Cache hashes.
+ * @private
+ */
+
+AbstractBlock.prototype.cacheHashes = co(function* cacheHashes() {
+  var i, tx;
+
+  yield this.hashAsync();
+
+  if (!this.txs)
+    return;
+
+  for (i = 0; i < this.txs.length; i++) {
+    tx = this.txs[i];
+    yield tx.hashAsync();
+  }
+});
+
 /**
  * Serialize the block headers.
  * @returns {Buffer}
diff --git a/lib/primitives/memblock.js b/lib/primitives/memblock.js
index c4a7e728..faefd321 100644
--- a/lib/primitives/memblock.js
+++ b/lib/primitives/memblock.js
@@ -78,6 +78,22 @@ MemBlock.fromOptions = function fromOptions(options) {
   return new MemBlock().fromOptions(options);
 };
 
+/**
+ * Serialize the block headers.
+ * @returns {Buffer}
+ */
+
+MemBlock.prototype.abbr = function abbr(writer) {
+  var data = this.raw.slice(0, 80);
+
+  if (writer) {
+    writer.writeBytes(data);
+    return writer;
+  }
+
+  return data;
+};
+
 /**
  * Get the full block size.
  * @returns {Number}
diff --git a/lib/primitives/tx.js b/lib/primitives/tx.js
index eba52316..590e7053 100644
--- a/lib/primitives/tx.js
+++ b/lib/primitives/tx.js
@@ -9,6 +9,7 @@
 
 var assert = require('assert');
 var util = require('../utils/util');
+var co = require('../utils/co');
 var crypto = require('../crypto/crypto');
 var btcutils = require('../btc/utils');
 var Amount = require('../btc/amount');
@@ -241,6 +242,35 @@ TX.prototype.hash = function _hash(enc) {
   return hash;
 };
 
+/**
+ * Hash the transaction with the non-witness serialization (async).
+ * @param {String?} enc - Can be `'hex'` or `null`.
+ * @returns {Hash|Buffer} hash
+ */
+
+TX.prototype.hashAsync = co(function* _hashAsync(enc) {
+  var hash = this._hash;
+  var hex;
+
+  if (!hash) {
+    hash = yield crypto.hash256Async(this.toNormal());
+    if (!this.mutable)
+      this._hash = hash;
+  }
+
+  if (enc === 'hex') {
+    hex = this._hhash;
+    if (!hex) {
+      hex = hash.toString('hex');
+      if (!this.mutable)
+        this._hhash = hex;
+    }
+    hash = hex;
+  }
+
+  return hash;
+});
+
 /**
  * Hash the transaction with the witness
  * serialization, return the wtxid (normal
diff --git a/lib/protocol/constants.js b/lib/protocol/constants.js
index 56ecb2e6..40e924b2 100644
--- a/lib/protocol/constants.js
+++ b/lib/protocol/constants.js
@@ -698,6 +698,22 @@ exports.ZERO_SIG64 = new Buffer(''
   'hex'
 );
 
+/**
+ * 4 zero bytes.
+ * @const {Buffer}
+ * @default
+ */
+
+exports.ZERO_U32 = new Buffer('00000000', 'hex');
+
+/**
+ * 8 zero bytes.
+ * @const {Buffer}
+ * @default
+ */
+
+exports.ZERO_U64 = new Buffer('0000000000000000', 'hex');
+
 /**
  * BCoin version.
  * @const {String}
diff --git a/lib/utils/reader.js b/lib/utils/reader.js
index 90faa1e8..54595746 100644
--- a/lib/utils/reader.js
+++ b/lib/utils/reader.js
@@ -595,7 +595,7 @@ BufferReader.prototype.readNullString = function readNullString(enc) {
 BufferReader.prototype.createChecksum = function createChecksum() {
   var start = this.stack[this.stack.length - 1] || 0;
   var data = this.data.slice(start, this.offset);
-  return crypto.checksum(data).readUInt32LE(0, true);
+  return crypto.hash256(data).readUInt32LE(0, true);
 };
 
 /**
diff --git a/lib/utils/util.js b/lib/utils/util.js
index a6b0ea53..4b226f93 100644
--- a/lib/utils/util.js
+++ b/lib/utils/util.js
@@ -13,7 +13,6 @@ var assert = require('assert');
 var nodeUtil = require('util');
 var fs = require('fs');
 var os = require('os');
-var BN = require('bn.js');
 var util = exports;
 var Number, Math, Date;
 
@@ -542,38 +541,14 @@ util.time = function time(date) {
 
 /**
  * Create a 64 bit nonce.
- * @returns {BN}
+ * @returns {Buffer}
  */
 
-util.nonce = function _nonce(buffer) {
+util.nonce = function _nonce() {
   var nonce = new Buffer(8);
-
   nonce.writeUInt32LE((Math.random() * 0x100000000) >>> 0, 0, true);
   nonce.writeUInt32LE((Math.random() * 0x100000000) >>> 0, 4, true);
-
-  if (buffer)
-    return nonce;
-
-  return new BN(nonce);
-};
-
-/**
- * Test whether a buffer is all zeroes.
- * @param {Buffer} data
- * @returns {Boolean}
- */
-
-util.isZero = function isZero(data) {
-  var i;
-
-  assert(Buffer.isBuffer(data));
-
-  for (i = 0; i < data.length; i++) {
-    if (data[i] !== 0)
-      return false;
-  }
-
-  return true;
+  return nonce;
 };
 
 /**
@@ -1015,3 +990,21 @@ util._paths = {};
 util.fastProp = function fastProp(obj) {
   ({ __proto__: obj });
 };
+
+/**
+ * Promisify a function.
+ * @param {Function} func
+ * @returns {Function}
+ */
+
+util.promisify = function promisify(func) {
+  return function() {
+    var result;
+    try {
+      result = func.apply(this, arguments);
+    } catch (e) {
+      return Promise.reject(e);
+    }
+    return Promise.resolve(result);
+  };
+};
diff --git a/lib/utils/writer.js b/lib/utils/writer.js
index 41f9d8b3..3ab86687 100644
--- a/lib/utils/writer.js
+++ b/lib/utils/writer.js
@@ -105,7 +105,7 @@ BufferWriter.prototype.render = function render(keep) {
       case BYTES: off += item[1].copy(data, off); break;
       case STR: off += data.write(item[1], off, item[2]); break;
       case CHECKSUM:
-        off += crypto.checksum(data.slice(0, off)).copy(data, off);
+        off += crypto.hash256(data.slice(0, off)).copy(data, off, 0, 4);
         break;
       case FILL:
         data.fill(item[1], off, off + item[2]);
diff --git a/lib/wallet/masterkey.js b/lib/wallet/masterkey.js
index c70dfab6..efbed89a 100644
--- a/lib/wallet/masterkey.js
+++ b/lib/wallet/masterkey.js
@@ -15,6 +15,12 @@ var BufferReader = require('../utils/reader');
 var BufferWriter = require('../utils/writer');
 var HD = require('../hd/hd');
 
+/*
+ * Constants
+ */
+
+var BCOIN_SALT = new Buffer('bcoin', 'ascii');
+
 /**
  * Master BIP32 key which can exist
  * in a timed out encrypted state.
@@ -234,11 +240,14 @@ MasterKey.prototype.stop = function stop() {
  */
 
 MasterKey.prototype.derive = function derive(passwd) {
+  if (typeof passwd === 'string')
+    passwd = new Buffer(passwd, 'utf8');
+
   switch (this.alg) {
     case MasterKey.alg.PBKDF2:
-      return crypto.pbkdf2Async(passwd, 'bcoin', this.N, 32, 'sha256');
+      return crypto.pbkdf2Async(passwd, BCOIN_SALT, this.N, 32, 'sha256');
     case MasterKey.alg.SCRYPT:
-      return crypto.scryptAsync(passwd, 'bcoin', this.N, this.r, this.p, 32);
+      return crypto.scryptAsync(passwd, BCOIN_SALT, this.N, this.r, this.p, 32);
     default:
       return Promise.reject(new Error('Unknown algorithm: ' + this.alg));
   }
diff --git a/package.json b/package.json
index cda31bb1..e1bb5905 100644
--- a/package.json
+++ b/package.json
@@ -41,7 +41,7 @@
     "elliptic": "6.3.2"
   },
   "optionalDependencies": {
-    "bcoin-native": "0.0.9",
+    "bcoin-native": "0.0.10",
     "leveldown": "1.5.0",
     "secp256k1": "3.2.0",
     "socket.io": "1.4.8",
diff --git a/test/aes-test.js b/test/aes-test.js
index 8a0d23c5..3924b9b3 100644
--- a/test/aes-test.js
+++ b/test/aes-test.js
@@ -58,6 +58,38 @@ describe('AES', function() {
     ]);
   }
 
+  function bencrypt(data, passphrase) {
+    var key, cipher;
+
+    assert(nativeCrypto, 'No crypto module available.');
+    assert(passphrase, 'No passphrase.');
+
+    if (typeof data === 'string')
+      data = new Buffer(data, 'utf8');
+
+    if (typeof passphrase === 'string')
+      passphrase = new Buffer(passphrase, 'utf8');
+
+    key = pbkdf2key(passphrase, 2048, 32, 16);
+    return crypto.encipher(data, key.key, key.iv);
+  }
+
+  function bdecrypt(data, passphrase) {
+    var key, decipher;
+
+    assert(nativeCrypto, 'No crypto module available.');
+    assert(passphrase, 'No passphrase.');
+
+    if (typeof data === 'string')
+      data = new Buffer(data, 'hex');
+
+    if (typeof passphrase === 'string')
+      passphrase = new Buffer(passphrase, 'utf8');
+
+    key = pbkdf2key(passphrase, 2048, 32, 16);
+    return crypto.decipher(data, key.key, key.iv);
+  }
+
   function encrypt(data, passphrase) {
     var key, cipher;
 
@@ -101,9 +133,14 @@ describe('AES', function() {
     var enchash2 = nencrypt(hash2, 'foo');
     var dechash2 = ndecrypt(enchash2, 'foo');
 
+    var hash3 = crypto.sha256(new Buffer([]));
+    var enchash3 = bencrypt(hash3, 'foo');
+    var dechash3 = bdecrypt(enchash3, 'foo');
+
     assert.deepEqual(hash, hash2);
     assert.deepEqual(enchash, enchash2);
     assert.deepEqual(dechash, dechash2);
+    assert.deepEqual(dechash, dechash3);
   });
 
   it('should encrypt and decrypt a hash with uneven blocks', function() {
diff --git a/test/scrypt-test.js b/test/scrypt-test.js
index 7de5c701..158f45cd 100644
--- a/test/scrypt-test.js
+++ b/test/scrypt-test.js
@@ -5,7 +5,9 @@ var scrypt = require('../lib/crypto/crypto').scrypt;
 
 describe('Scrypt', function() {
   it('should perform scrypt with N=16', function() {
-    var result = scrypt('', '', 16, 1, 1, 64);
+    var pass = new Buffer('');
+    var salt = new Buffer('');
+    var result = scrypt(pass, salt, 16, 1, 1, 64);
     assert.equal(result.toString('hex'), ''
       + '77d6576238657b203b19ca42c18a0497f16b4844e3074ae8dfdffa3f'
       + 'ede21442fcd0069ded0948f8326a753a0fc81f17e8d3e0fb2e0d3628'
@@ -13,7 +15,9 @@ describe('Scrypt', function() {
   });
 
   it('should perform scrypt with N=1024', function() {
-    var result = scrypt('password', 'NaCl', 1024, 8, 16, 64);
+    var pass = new Buffer('password');
+    var salt = new Buffer('NaCl');
+    var result = scrypt(pass, salt, 1024, 8, 16, 64);
     assert.equal(result.toString('hex'), ''
       + 'fdbabe1c9d3472007856e7190d01e9fe7c6ad7cbc8237830e773'
       + '76634b3731622eaf30d92e22a3886ff109279d9830dac727afb9'
@@ -21,7 +25,9 @@ describe('Scrypt', function() {
   });
 
   it('should perform scrypt with N=16384', function() {
-    var result = scrypt('pleaseletmein', 'SodiumChloride', 16384, 8, 1, 64);
+    var pass = new Buffer('pleaseletmein');
+    var salt = new Buffer('SodiumChloride');
+    var result = scrypt(pass, salt, 16384, 8, 1, 64);
     assert.equal(result.toString('hex'), ''
       + '7023bdcb3afd7348461c06cd81fd38ebfda8fbba904f8e3ea9b54'
       + '3f6545da1f2d5432955613f0fcf62d49705242a9af9e61e85dc0d'
@@ -30,7 +36,9 @@ describe('Scrypt', function() {
 
   // Only enable if you want to wait a while.
   // it('should perform scrypt with N=1048576', function() {
-  //   var result = scrypt('pleaseletmein', 'SodiumChloride', 1048576, 8, 1, 64);
+  //   var pass = new Buffer('pleaseletmein');
+  //   var salt = new Buffer('SodiumChloride');
+  //   var result = scrypt(pass, salt, 1048576, 8, 1, 64);
   //   assert.equal(result.toString('hex'), ''
   //     + '2101cb9b6a511aaeaddbbe09cf70f881ec568d574a2ffd4dabe5'
   //     + 'ee9820adaa478e56fd8f4ba5d09ffa1c6d927c40f4c337304049'