diff --git a/Identity.cpp b/Identity.cpp
index b80d1cbf..f57ab97b 100644
--- a/Identity.cpp
+++ b/Identity.cpp
@@ -1,3 +1,5 @@
+#include <time.h>
+#include <stdio.h>
 #include <cryptopp/sha.h>
 #include <cryptopp/osrng.h>
 #include <cryptopp/dh.h>
@@ -43,5 +45,30 @@ namespace data
 		
 		return keys;
 	}	
+
+	RoutingKey CreateRoutingKey (const IdentHash& ident)
+	{
+		uint8_t buf[41]; // ident + yyyymmdd
+		memcpy (buf, (const uint8_t *)ident, 32);
+		time_t t = time (nullptr);
+		struct tm tm;
+		gmtime_r (&t, &tm);
+		sprintf ((char *)(buf + 32),"%4i%2i%2i", tm.tm_year, tm.tm_mon, tm.tm_mday);
+		
+		RoutingKey key;
+		CryptoPP::SHA256().CalculateDigest(key.hash, buf, 40);
+		return key;
+	}	
+	
+	XORMetric operator^(const RoutingKey& key1, const RoutingKey& key2)
+	{
+		// TODO: implementation depends on CPU
+		XORMetric m;
+		((uint64_t *)m.metric)[0] = ((uint64_t *)key1.hash)[0] ^ ((uint64_t *)key2.hash)[0];
+		((uint64_t *)m.metric)[1] = ((uint64_t *)key1.hash)[1] ^ ((uint64_t *)key2.hash)[1];
+		((uint64_t *)m.metric)[2] = ((uint64_t *)key1.hash)[2] ^ ((uint64_t *)key2.hash)[2];
+		((uint64_t *)m.metric)[3] = ((uint64_t *)key1.hash)[3] ^ ((uint64_t *)key2.hash)[3];
+		return m;
+	}	
 }
 }
diff --git a/Identity.h b/Identity.h
index 549e9cea..9e8b62ac 100644
--- a/Identity.h
+++ b/Identity.h
@@ -57,7 +57,26 @@ namespace data
 
 	IdentHash CalculateIdentHash (const Identity& identity);
 	Keys CreateRandomKeys ();
+
+	// kademlia
+	struct RoutingKey
+	{
+		uint8_t hash[32];
+	};	
+
+	struct XORMetric
+	{
+		uint8_t metric[32];
+
+		void SetMin () { memset (metric, 0, 32); };
+		void SetMax () { memset (metric, 0xFF, 32); };
+		bool operator< (const XORMetric& other) const { return memcmp (metric, other.metric, 32) < 0; };
+	};	
+
+	RoutingKey CreateRoutingKey (const IdentHash& ident);
+	XORMetric operator^(const RoutingKey& key1, const RoutingKey& key2); 	
 	
+	// destination for delivery instuctions
 	class RoutingDestination
 	{
 		public:
diff --git a/NetDb.cpp b/NetDb.cpp
index 77e2ce72..89364c1b 100644
--- a/NetDb.cpp
+++ b/NetDb.cpp
@@ -388,5 +388,26 @@ namespace data
 	{
 		if (msg) m_Queue.Put (msg);	
 	}	
+
+	const RouterInfo * NetDb::GetClosestFloodfill (const IdentHash& destination) const
+	{
+		RouterInfo * r = nullptr;
+		XORMetric minMetric;
+		RoutingKey destKey = CreateRoutingKey (destination);
+		minMetric.SetMax ();
+		for (auto it: m_RouterInfos)
+		{	
+			if (it.second->IsFloodfill () &&! it.second->IsUnreachable ())
+			{	
+				XORMetric m = destKey ^ it.second->GetRoutingKey ();
+				if (m < minMetric)
+				{
+					minMetric = m;
+					r = it.second;
+				}
+			}	
+		}	
+		return r;
+	}	
 }
 }
diff --git a/NetDb.h b/NetDb.h
index ca63a239..761d3a09 100644
--- a/NetDb.h
+++ b/NetDb.h
@@ -48,6 +48,7 @@ namespace data
 			void SaveUpdated (const char * directory);
 			void Run (); // exploratory thread
 			void Explore ();
+			const RouterInfo * GetClosestFloodfill (const IdentHash& destination) const;
 			
 		private:
 
diff --git a/RouterInfo.cpp b/RouterInfo.cpp
index 417466c6..45ab4c20 100644
--- a/RouterInfo.cpp
+++ b/RouterInfo.cpp
@@ -35,6 +35,7 @@ namespace data
 		m_RouterIdentity = identity;
 		m_IdentHash = CalculateIdentHash (m_RouterIdentity);
 		UpdateIdentHashBase64 ();
+		UpdateRoutingKey ();
 		m_Timestamp = i2p::util::GetMillisecondsSinceEpoch ();
 	}
 	
@@ -126,6 +127,7 @@ namespace data
 		
 		CryptoPP::SHA256().CalculateDigest(m_IdentHash, (uint8_t *)&m_RouterIdentity, sizeof (m_RouterIdentity));
 		UpdateIdentHashBase64 ();
+		UpdateRoutingKey ();
 	}	
 
 	void RouterInfo::UpdateIdentHashBase64 ()
@@ -135,6 +137,11 @@ namespace data
 		memcpy (m_IdentHashAbbreviation, m_IdentHashBase64, 4);
 		m_IdentHashAbbreviation[4] = 0;
 	}	
+
+	void RouterInfo::UpdateRoutingKey ()
+	{		
+		m_RoutingKey = CreateRoutingKey (m_IdentHash);
+	}
 		
 	void RouterInfo::WriteToStream (std::ostream& s)
 	{
diff --git a/RouterInfo.h b/RouterInfo.h
index 3111fbf3..ceda10cb 100644
--- a/RouterInfo.h
+++ b/RouterInfo.h
@@ -46,6 +46,7 @@ namespace data
 			uint64_t GetTimestamp () const { return m_Timestamp; };
 			const std::vector<Address>& GetAddresses () const { return m_Addresses; };
 			Address * GetNTCPAddress ();
+			const RoutingKey& GetRoutingKey () const { return m_RoutingKey; };
 			
 			void AddNTCPAddress (const char * host, int port);
 			void SetProperty (const char * key, const char * value);
@@ -56,6 +57,7 @@ namespace data
 			bool IsUnreachable () const { return m_IsUnreachable; };
 			
 			void CreateBuffer ();
+			void UpdateRoutingKey ();
 			const char * GetBuffer () const  { return m_Buffer; };
 			int GetBufferLen () const { return m_BufferLen; };
 
@@ -81,6 +83,7 @@ namespace data
 
 			Identity m_RouterIdentity;
 			IdentHash m_IdentHash;
+			RoutingKey m_RoutingKey;
 			char m_IdentHashBase64[48], m_IdentHashAbbreviation[5];
 			char m_Buffer[2048];
 			int m_BufferLen;