diff --git a/lib/blockchain.js b/lib/blockchain.js
index 49cbafc8..6498491b 100644
--- a/lib/blockchain.js
+++ b/lib/blockchain.js
@@ -6,7 +6,11 @@ var _ = bitcore.deps._;
 
 function BlockChain() {
   this.tip = null;
-  this.headers = {};
+  this.work = {
+    '0000000000000000000000000000000000000000000000000000000000000000': 0
+  };
+  this.height = {};
+  this.hashByHeight = {};
   this.next = {};
   this.prev = {};
 }
@@ -14,26 +18,137 @@ function BlockChain() {
 BlockChain.fromObject = function(obj) {
   var blockchain = new BlockChain();
   blockchain.tip = obj.tip;
-  blockchain.headers = obj.headers;
+  blockchain.work = obj.work;
+  blockchain.hashByHeight = obj.hashByHeight;
+  blockchain.height = obj.height;
   blockchain.next = obj.next;
   blockchain.prev = obj.prev;
   return blockchain;
 };
 
-BlockChain.prototype.setTip = function(block) {
+var getWork = function(bits) {
+  var bytes = ((bits >>> 24) & 0xff) >>> 0;
+  return ((bits & 0xffffff) << (8 * (bytes - 3))) >>> 0;
+};
+
+BlockChain.prototype.addData = function(block) {
   $.checkArgument(block instanceof bitcore.Block, 'Argument is not a Block instance');
-  this.tip = block.hash;
-  this.headers[block.hash] = block.header;
+
   var prevHash = bitcore.util.buffer.reverse(block.header.prevHash).toString('hex');
-  this.next[prevHash] = block.hash;
+
+  this.work[block.hash] = this.work[prevHash].work + getWork(block.header.bits);
   this.prev[block.hash] = prevHash;
 };
 
+BlockChain.prototype.proposeNewBlock = function(block) {
+  $.checkArgument(block instanceof bitcore.Block, 'Argument is not a Block instance');
+  var prevHash = bitcore.util.buffer.reverse(block.header.prevHash).toString('hex');
+
+  if (!this.work[prevHash]) {
+    throw new Error('No previous data to estimate work');
+  }
+  this.addData(block);
+
+  if (this.work[block.hash] > this.work[this.tip]) {
+
+    var toUnconfirm = [];
+    var toConfirm = [];
+    var commonAncestor;
+
+    var pointer = block.hash;
+    while (!this.height[pointer]) {
+      toConfirm.push(pointer);
+      pointer = this.prev[pointer];
+    }
+    commonAncestor = pointer;
+
+    pointer = this.tip;
+    while (pointer !== commonAncestor) {
+      toUnconfirm.push(pointer);
+      pointer = this.prev[pointer];
+    }
+
+    toConfirm.reverse();
+
+    var self = this;
+    toUnconfirm.map(function(hash) {
+      self.unconfirm(hash);
+    });
+    toConfirm.map(function(hash) {
+      self.confirm(hash);
+    });
+    return {
+      unconfirmed: toUnconfirm,
+      confirmed: toConfirm
+    };
+  }
+  return {
+    unconfirmed: [],
+    confirmed: []
+  };
+};
+
+BlockChain.prototype.confirm = function(hash) {
+  var prevHash = this.prev[hash];
+  $.checkState(prevHash === this.tip);
+
+  this.tip = hash;
+  var height = this.height[prevHash] + 1;
+  this.next[prevHash] = hash;
+  this.hashByHeight[height] = hash;
+  this.height[hash] = height;
+};
+
+BlockChain.prototype.unconfirm = function(hash) {
+  var prevHash = this.prev[hash];
+  $.checkState(hash === this.tip);
+
+  this.tip = prevHash;
+  var height = this.height[hash];
+  delete this.next[prevHash];
+  delete this.hashByHeight[height];
+  delete this.height[hash];
+};
+
+BlockChain.prototype.getBlockLocator = function() {
+  $.checkState(this.tip);
+  $.checkState(this.height[this.tip]);
+
+  var result = [];
+  var currentHeight = this.height[this.tip];
+  var exponentialBackOff = 1;
+  for (var i = 0; i < 10; i++) {
+    result.push(this.hashByHeight[currentHeight--]);
+  }
+  while (currentHeight > 0) {
+    result.push(this.hashByHeight[currentHeight]);
+    currentHeight -= exponentialBackOff;
+    exponentialBackOff *= 2;
+  }
+  return result;
+};
+
+BlockChain.prototype.hasData = function(hash) {
+  return !!this.prev[hash];
+};
+
+BlockChain.prototype.prune = function() {
+  var self = this;
+  _.each(this.prev, function(key, value) {
+    if (!self.height[key]) {
+      delete this.prev[key];
+      delete this.work[key];
+    }
+  });
+};
+
 BlockChain.prototype.toObject = function() {
   return {
     tip: this.tip,
-    headers: _.map(this.headers, function(header) { return header.toObject(); }),
+    work: this.work,
     next: this.next,
+    hashByHeight: this.hashByHeight,
+    height: this.height,
     prev: this.prev
   };
 };