diff --git a/lib/pool.js b/lib/pool.js
index 2d0ca08..988118f 100644
--- a/lib/pool.js
+++ b/lib/pool.js
@@ -1,5 +1,7 @@
 var events = require('events');
 var async = require('async');
+
+var varDiff = require('./varDifff.js');
 var daemon = require('./daemon.js');
 var stratum = require('./stratum.js');
 var jobManager = require('./jobManager.js');
@@ -22,6 +24,7 @@ var util = require('./util.js');
 var pool = module.exports = function pool(options, authorizeFn){
 
     this.options = options;
+
     var _this = this;
     var publicKeyBuffer;
 
@@ -32,10 +35,34 @@ var pool = module.exports = function pool(options, authorizeFn){
 
     (function Init(){
         SetupJobManager();
+        SetupVarDiff();
         SetupDaemonInterface();
     })();
 
 
+    function SetupVarDiff(){
+        _this.varDiff = new varDifff(options.varDiff, options.difficulty);
+        _this.varDiff.on('difficultyRequest', function(){
+            emitLog('varDiff', 'Difficulty requested for vardiff');
+            if (_this.stratumServer)
+                RequestDifficulty(function(){});
+        });
+    }
+
+    function RequestDifficulty(callback){
+        _this.daemon.cmd('getdifficulty',
+            [],
+            function(error, result){
+                if (error) {
+                    emitErrorLog('getdifficulty', 'Error requesting difficulty from daemon for vardiff');
+                } else {
+                    _this.varDiff.setNetworkDifficulty(result);
+                    callback(error, result);
+                }
+            }
+        );
+    }
+
     /*
     Coin daemons either use submitblock or getblocktemplate for submitting new blocks
      */
@@ -108,6 +135,7 @@ var pool = module.exports = function pool(options, authorizeFn){
         _this.daemon = new daemon.interface(options.daemon);
         _this.daemon.on('online', function(){
             async.parallel({
+                difficulty: RequestDifficulty,
                 addressInfo: function(callback){
                     _this.daemon.cmd('validateaddress',
                         [options.address],
@@ -178,6 +206,9 @@ var pool = module.exports = function pool(options, authorizeFn){
             emitLog('system','Stratum server started on port ' + options.stratumPort);
             _this.emit('started');
         }).on('client.connected', function(client){
+
+            _this.varDiff.manageClient(client);
+
             client.on('subscription', function(params, resultCallback){
 
                 var extraNonce = _this.jobManager.extraNonceCounter.next();
diff --git a/lib/varDifff.js b/lib/varDifff.js
new file mode 100644
index 0000000..ba90c02
--- /dev/null
+++ b/lib/varDifff.js
@@ -0,0 +1,128 @@
+var events = require('events');
+
+/*
+
+Vardiff ported from stratum-mining share-limiter
+ https://github.com/ahmedbodi/stratum-mining/blob/master/mining/basic_share_limiter.py
+
+ */
+
+
+function RingBuffer(maxSize){
+    var data = [];
+    var cursor = 0;
+    var isFull = false;
+    this.append = function(x){
+        if (isFull){
+            data[cursor] = x;
+            cursor = (cursor + 1) % maxSize;
+        }
+        else{
+            data.push(x);
+            cursor++;
+            if (data.length === maxSize){
+                cursor = 0;
+                isFull = true;
+            }
+        }
+    };
+    this.avg = function(){
+        var total = data.reduce(function(a, b){
+            return a + b;
+        });
+        return total / (isFull ? maxSize : cursor);
+    };
+    this.size = function(){
+        return isFull ? maxSize : cursor;
+    };
+    this.clear = function(){
+        data = [];
+        cursor = 0;
+        isFull = false;
+    };
+}
+
+
+var varDiff = module.exports = function varDiff(options, poolDifficulty){
+
+    var _this = this;
+
+    if (!options.enabled){
+        return;
+    }
+
+    var networkDifficulty;
+    var bufferSize = options.retargetTime / options.targetTime * 4;
+    var variance = options.targetTime * (options.variancePercent / 100);
+    var tMin = options.targetTime - variance;
+    var tMax = options.targetTime + variance;
+
+    this.setNetworkDifficulty = function(diff){
+        networkDifficulty = diff;
+    };
+
+    setInterval(function(){
+        _this.emit('difficultyRequest');
+    }, options.daemonDiffUpdateFrequency * 1000);
+
+    this.manageClient = function(client){
+        var lastTs;
+        var lastRtc;
+        var timeBuffer;
+
+        client.on('submit', function(){
+
+            var ts = Date.now() / 1000;
+
+            if (!lastRtc){
+                lastRtc = ts - options.retargetTime / 2;
+                lastTs = ts;
+                timeBuffer = new RingBuffer(bufferSize);
+                console.log('first time share vardiff');
+                return;
+            }
+
+            timeBuffer.append(ts - lastTs);
+            lastTs = ts;
+
+            if ((ts - lastRtc) < options.retargetTime && timeBuffer.size() > 0){
+                console.log('do not retarget');
+                return;
+            }
+
+            lastRtc = ts;
+            var avg = timeBuffer.avg();
+
+            if (avg < 1)
+                avg = 1;
+
+            var ddiff = (client.difficulty * (options.targetTime / avg)) - client.difficulty;
+
+            if (avg > tMax && client.difficulty > options.minDifficulty){
+                if (ddiff > -1)
+                    ddiff = -1;
+                if (ddiff + client.difficulty < poolDifficulty)
+                    ddiff = options.minDifficulty - client.difficulty;
+            }
+            else if (avg < tMin){
+                if (ddiff < 1)
+                    ddiff = 1;
+                var diffMax = networkDifficulty < options.maxDifficulty ? networkDifficulty : options.maxDifficulty;
+                if (ddiff + client.difficulty > diffMax)
+                    ddiff = diffMax - client.difficulty;
+            }
+            else{
+                console.log('hashrate in range ' + JSON.stringify({ddiff: ddiff, avg: avg}) );
+                return;
+            }
+
+            var newDiff = client.difficulty * ddiff;
+            timeBuffer.clear();
+
+            console.log('sending new difficutly ' + newDiff);
+
+            client.sendDifficulty(newDiff);
+        });
+    };
+};
+varDiff.prototype.__proto__ = events.EventEmitter.prototype;
\ No newline at end of file
diff --git a/lib/vardiff.js b/lib/vardiff.js
deleted file mode 100644
index e69de29..0000000