diff --git a/lib/http/rpc.js b/lib/http/rpc.js
index f9b2340f..9b1bd7e6 100644
--- a/lib/http/rpc.js
+++ b/lib/http/rpc.js
@@ -915,7 +915,7 @@ RPC.prototype._submitWork = co(function* _submitWork(data) {
   var header = Headers.fromAbbr(data);
   var nonce = header.nonce;
   var ts = header.ts;
-  var job, n1, n2, hash, block, entry;
+  var job, n1, n2, proof, block, entry;
 
   if (!attempt)
     return false;
@@ -942,12 +942,12 @@ RPC.prototype._submitWork = co(function* _submitWork(data) {
   n1 = job.nonce1;
   n2 = job.nonce2;
 
-  hash = attempt.hash(n1, n2, ts, nonce);
+  proof = attempt.getProof(n1, n2, ts, nonce);
 
-  if (!consensus.verifyPOW(hash, attempt.bits))
+  if (!proof.verify(attempt.target))
     return false;
 
-  block = attempt.commit(n1, n2, ts, nonce);
+  block = attempt.commit(proof);
 
   try {
     entry = yield this.chain.add(block);
@@ -983,12 +983,14 @@ RPC.prototype._createWork = co(function* _createWork() {
   var n1 = this.nonce1;
   var n2 = this.nonce2;
   var ts = attempt.ts;
-  var data, head;
+  var data, root, head;
 
   data = new Buffer(128);
   data.fill(0);
 
-  head = attempt.getHeader(n1, n2, ts, 0);
+  root = attempt.getRoot(n1, n2);
+  head = attempt.getHeader(root, ts, 0);
+
   head.copy(data, 0);
 
   data[80] = 0x80;
diff --git a/lib/mining/common.js b/lib/mining/common.js
new file mode 100644
index 00000000..bc677df6
--- /dev/null
+++ b/lib/mining/common.js
@@ -0,0 +1,124 @@
+/*!
+ * common.js - mining utils
+ * Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
+ * https://github.com/bcoin-org/bcoin
+ */
+
+'use strict';
+
+var assert = require('assert');
+
+/**
+ * @exports mining/common
+ */
+
+var common = exports;
+
+/*
+ * Constants
+ */
+
+var DIFF_TARGET = 0x00000000ffff0000000000000000000000000000000000000000000000000000;
+var B192 = 0x1000000000000000000000000000000000000000000000000;
+var B128 = 0x100000000000000000000000000000000;
+var B64 = 0x10000000000000000;
+var B0 = 0x1;
+
+/**
+ * Swap 32 bit endianness of uint256.
+ * @param {Buffer} data
+ * @returns {Buffer}
+ */
+
+exports.swap32 = function swap32(data) {
+  var i, field;
+
+  for (i = 0; i < data.length; i += 4) {
+    field = data.readUInt32LE(i, true);
+    data.writeUInt32BE(field, i, true);
+  }
+
+  return data;
+};
+
+/**
+ * Swap 32 bit endianness of uint256 (hex).
+ * @param {String} data
+ * @returns {String}
+ */
+
+exports.hswap32 = function hswap32(hex) {
+  var data = new Buffer(hex, 'hex');
+  exports.swap32(data)
+  return data.toString('hex');
+};
+
+/**
+ * Compare two uint256le's.
+ * @param {Buffer} a
+ * @param {Buffer} b
+ * @returns {Number}
+ */
+
+exports.rcmp = function rcmp(a, b) {
+  var i;
+
+  assert(a.length === b.length);
+
+  for (i = a.length - 1; i >= 0; i--) {
+    if (a[i] < b[i])
+      return -1;
+    if (a[i] > b[i])
+      return 1;
+  }
+
+  return 0;
+};
+
+/**
+ * Convert a uint256le to a double.
+ * @param {Buffer} target
+ * @returns {Number}
+ */
+
+exports.double256 = function double256(target) {
+  var n = 0;
+  var hi, lo;
+
+  assert(target.length === 32);
+
+  hi = target.readUInt32LE(28, true);
+  lo = target.readUInt32LE(24, true);
+  n += (hi * 0x100000000 + lo) * B192;
+
+  hi = target.readUInt32LE(20, true);
+  lo = target.readUInt32LE(16, true);
+  n += (hi * 0x100000000 + lo) * B128;
+
+  hi = target.readUInt32LE(12, true);
+  lo = target.readUInt32LE(8, true);
+  n += (hi * 0x100000000 + lo) * B64;
+
+  hi = target.readUInt32LE(4, true);
+  lo = target.readUInt32LE(0, true);
+  n += (hi * 0x100000000 + lo) * B0;
+
+  return n;
+};
+
+/**
+ * Calculate mining difficulty
+ * from little-endian target.
+ * @param {Buffer} target
+ * @returns {Number}
+ */
+
+exports.getDifficulty = function getDifficulty(target) {
+  var d = DIFF_TARGET;
+  var n = exports.double256(target);
+  if (n === 0)
+    return d;
+  if (n > d)
+    return d;
+  return Math.floor(d / n);
+};
diff --git a/lib/mining/cpuminer.js b/lib/mining/cpuminer.js
index 71c23650..13511f47 100644
--- a/lib/mining/cpuminer.js
+++ b/lib/mining/cpuminer.js
@@ -279,7 +279,7 @@ CPUMiner.prototype.notifyEntry = function notifyEntry() {
  */
 
 CPUMiner.prototype.findNonce = function findNonce(job) {
-  var data = job.getHeader(0);
+  var data = job.getHeader();
   var target = job.attempt.target;
   var interval = CPUMiner.INTERVAL;
   var min = 0;
@@ -309,7 +309,7 @@ CPUMiner.prototype.findNonce = function findNonce(job) {
  */
 
 CPUMiner.prototype.findNonceAsync = co(function* findNonceAsync(job) {
-  var data = job.getHeader(0);
+  var data = job.getHeader();
   var target = job.attempt.target;
   var interval = CPUMiner.INTERVAL;
   var min = 0;
@@ -439,12 +439,14 @@ function CPUJob(miner, attempt) {
  * @returns {Buffer}
  */
 
-CPUJob.prototype.getHeader = function getHeader(nonce) {
+CPUJob.prototype.getHeader = function getHeader() {
   var attempt = this.attempt;
   var n1 = this.nonce1;
   var n2 = this.nonce2;
   var ts = attempt.ts;
-  return this.attempt.getHeader(n1, n2, ts, nonce);
+  var root = attempt.getRoot(n1, n2);
+  var data = attempt.getHeader(root, ts, 0);
+  return data;
 };
 
 /**
@@ -458,11 +460,14 @@ CPUJob.prototype.commit = function commit(nonce) {
   var n1 = this.nonce1;
   var n2 = this.nonce2;
   var ts = attempt.ts;
+  var proof;
 
   assert(!this.committed, 'Job already committed.');
   this.committed = true;
 
-  return this.attempt.commit(n1, n2, ts, nonce);
+  proof = attempt.getProof(n1, n2, ts, nonce);
+
+  return attempt.commit(proof);
 };
 
 /**
diff --git a/lib/mining/index.js b/lib/mining/index.js
index 6e5ddd59..e56c54a4 100644
--- a/lib/mining/index.js
+++ b/lib/mining/index.js
@@ -5,6 +5,7 @@
  */
 
 exports.BlockTemplate = require('./template');
+exports.common = require('./common');
 exports.CPUMiner = require('./cpuminer');
 exports.mine = require('./mine');
 exports.Miner = require('./miner');
diff --git a/lib/mining/template.js b/lib/mining/template.js
index 662b299f..2b5e410d 100644
--- a/lib/mining/template.js
+++ b/lib/mining/template.js
@@ -21,6 +21,7 @@ var consensus = require('../protocol/consensus');
 var policy = require('../protocol/policy');
 var encoding = require('../utils/encoding');
 var CoinView = require('../coins/coinview');
+var common = require('./common');
 var DUMMY = new Buffer(0);
 
 /**
@@ -60,7 +61,7 @@ function BlockTemplate(options) {
  * @returns {Buffer}
  */
 
-BlockTemplate.prototype.commitmentHash = function commitmentHash() {
+BlockTemplate.prototype.getWitnessHash = function getWitnessHash() {
   var nonce = encoding.ZERO_HASH;
   var leaves = [];
   var i, item, root, data;
@@ -139,7 +140,7 @@ BlockTemplate.prototype.createCoinbase = function createCoinbase() {
   if (this.witness) {
     // Commitment output.
     commit = new Output();
-    hash = this.commitmentHash();
+    hash = this.getWitnessHash();
     commit.script.fromCommitment(hash);
     cb.outputs.push(commit);
   }
@@ -220,7 +221,7 @@ BlockTemplate.prototype.refresh = function refresh() {
  * @returns {Buffer}
  */
 
-BlockTemplate.prototype.getCoinbase = function getCoinbase(nonce1, nonce2) {
+BlockTemplate.prototype.getRawCoinbase = function getRawCoinbase(nonce1, nonce2) {
   var size = 0;
   var bw;
 
@@ -245,23 +246,21 @@ BlockTemplate.prototype.getCoinbase = function getCoinbase(nonce1, nonce2) {
  */
 
 BlockTemplate.prototype.getRoot = function getRoot(nonce1, nonce2) {
-  var raw = this.getCoinbase(nonce1, nonce2);
+  var raw = this.getRawCoinbase(nonce1, nonce2);
   var hash = crypto.hash256(raw);
   return this.tree.withFirst(hash);
 };
 
 /**
  * Create raw block header with given parameters.
- * @param {Number} nonce1
- * @param {Number} nonce2
+ * @param {Buffer} root
  * @param {Number} ts
  * @param {Number} nonce
  * @returns {Buffer}
  */
 
-BlockTemplate.prototype.getHeader = function getHeader(nonce1, nonce2, ts, nonce) {
+BlockTemplate.prototype.getHeader = function getHeader(root, ts, nonce) {
   var bw = new StaticWriter(80);
-  var root = this.getRoot(nonce1, nonce2);
 
   bw.writeU32(this.version);
   bw.writeHash(this.prevBlock);
@@ -274,17 +273,19 @@ BlockTemplate.prototype.getHeader = function getHeader(nonce1, nonce2, ts, nonce
 };
 
 /**
- * Calculate block hash with given parameters.
+ * Calculate proof with given parameters.
  * @param {Number} nonce1
  * @param {Number} nonce2
  * @param {Number} ts
  * @param {Number} nonce
- * @returns {Buffer}
+ * @returns {BlockProof}
  */
 
-BlockTemplate.prototype.hash = function hash(nonce1, nonce2, ts, nonce) {
-  var data = this.getHeader(nonce1, nonce2, ts, nonce);
-  return crypto.hash256(data);
+BlockTemplate.prototype.getProof = function getProof(nonce1, nonce2, ts, nonce) {
+  var root = this.getRoot(nonce1, nonce2);
+  var data = this.getHeader(root, ts, nonce);
+  var hash = crypto.hash256(data);
+  return new BlockProof(hash, root, nonce1, nonce2, ts, nonce);
 };
 
 /**
@@ -294,8 +295,8 @@ BlockTemplate.prototype.hash = function hash(nonce1, nonce2, ts, nonce) {
  * @returns {TX}
  */
 
-BlockTemplate.prototype.coinbase = function coinbase(nonce1, nonce2) {
-  var raw = this.getCoinbase(nonce1, nonce2);
+BlockTemplate.prototype.getCoinbase = function getCoinbase(nonce1, nonce2) {
+  var raw = this.getRawCoinbase(nonce1, nonce2);
   var tx = TX.fromRaw(raw);
   var input;
 
@@ -310,19 +311,19 @@ BlockTemplate.prototype.coinbase = function coinbase(nonce1, nonce2) {
 };
 
 /**
- * Create block from given parameters.
- * @param {Number} nonce1
- * @param {Number} nonce2
- * @param {Number} ts
- * @param {Number} nonce
+ * Create block from calculated proof.
+ * @param {BlockProof} proof
  * @returns {Block}
  */
 
-BlockTemplate.prototype.commit = function commit(nonce1, nonce2, ts, nonce) {
-  var tx = this.coinbase(nonce1, nonce2);
-  var root = this.tree.withFirst(tx.hash());
+BlockTemplate.prototype.commit = function commit(proof) {
+  var root = proof.root;
+  var n1 = proof.nonce1;
+  var n2 = proof.nonce2;
+  var ts = proof.ts;
+  var nonce = proof.nonce;
   var block = new Block();
-  var i, item;
+  var i, tx, item;
 
   block.version = this.version;
   block.prevBlock = this.prevBlock;
@@ -331,6 +332,8 @@ BlockTemplate.prototype.commit = function commit(nonce1, nonce2, ts, nonce) {
   block.bits = this.bits;
   block.nonce = nonce;
 
+  tx = this.getCoinbase(n1, n2);
+
   block.txs.push(tx);
 
   for (i = 0; i < this.items.length; i++) {
@@ -348,7 +351,7 @@ BlockTemplate.prototype.commit = function commit(nonce1, nonce2, ts, nonce) {
  */
 
 BlockTemplate.prototype.toCoinbase = function toCoinbase() {
-  return this.coinbase(0, 0);
+  return this.getCoinbase(0, 0);
 };
 
 /**
@@ -358,7 +361,17 @@ BlockTemplate.prototype.toCoinbase = function toCoinbase() {
  */
 
 BlockTemplate.prototype.toBlock = function toBlock() {
-  return this.commit(0, 0, this.ts, 0);
+  var proof = this.getProof(0, 0, this.ts, 0);
+  return this.commit(proof);
+};
+
+/**
+ * Calculate the target difficulty.
+ * @returns {Number}
+ */
+
+BlockTemplate.prototype.getDifficulty = function getDifficulty() {
+  return common.getDifficulty(this.target);
 };
 
 /**
@@ -601,6 +614,38 @@ MerkleTree.fromLeaves = function fromLeaves(leaves) {
   return new MerkleTree().fromLeaves(leaves);
 };
 
+/*
+ * BlockProof
+ * @constructor
+ * @param {Hash} hash
+ * @param {Hash} root
+ * @param {Number} nonce1
+ * @param {Number} nonce2
+ * @param {Number} ts
+ * @param {Number} nonce
+ */
+
+function BlockProof(hash, root, nonce1, nonce2, ts, nonce) {
+  this.hash = hash;
+  this.root = root;
+  this.nonce1 = nonce1;
+  this.nonce2 = nonce2;
+  this.ts = ts;
+  this.nonce = nonce;
+}
+
+BlockProof.prototype.rhash = function rhash() {
+  return util.revHex(this.hash.toString('hex'));
+};
+
+BlockProof.prototype.verify = function verify(target) {
+  return common.rcmp(this.hash, target) <= 0;
+};
+
+BlockProof.prototype.getDifficulty = function getDifficulty() {
+  return common.getDifficulty(this.hash);
+};
+
 /*
  * Helpers
  */