diff --git a/alethzero/MainWin.cpp b/alethzero/MainWin.cpp
index e48b58283..4655240e3 100644
--- a/alethzero/MainWin.cpp
+++ b/alethzero/MainWin.cpp
@@ -1718,7 +1718,7 @@ void Main::on_blocks_currentItemChanged()
 			s << "<div>Seed hash: <b>" << info.seedHash() << "</b>" << "</div>";
 			s << "<div>Mix hash: <b>" << info.mixHash << "</b>" << "</div>";
 			s << "<div>Nonce: <b>" << info.nonce << "</b>" << "</div>";
-			s << "<div>Hash w/o nonce: <b>" << info.headerHash(WithoutNonce) << "</b>" << "</div>";
+			s << "<div>Hash w/o nonce: <b>" << info.headerHash(WithoutProof) << "</b>" << "</div>";
 			s << "<div>Difficulty: <b>" << info.difficulty << "</b>" << "</div>";
 			if (info.number)
 			{
@@ -1749,7 +1749,7 @@ void Main::on_blocks_currentItemChanged()
 				s << line << "Seed hash: <b>" << uncle.seedHash() << "</b>" << "</div>";
 				s << line << "Mix hash: <b>" << uncle.mixHash << "</b>" << "</div>";
 				s << line << "Nonce: <b>" << uncle.nonce << "</b>" << "</div>";
-				s << line << "Hash w/o nonce: <b>" << uncle.headerHash(WithoutNonce) << "</b>" << "</div>";
+				s << line << "Hash w/o nonce: <b>" << uncle.headerHash(WithoutProof) << "</b>" << "</div>";
 				s << line << "Difficulty: <b>" << uncle.difficulty << "</b>" << "</div>";
 				auto e = EthashAux::eval(uncle);
 				s << line << "Proof-of-Work: <b>" << e.value << " &lt;= " << (h256)u256((bigint(1) << 256) / uncle.difficulty) << "</b> (mixhash: " << e.mixHash.abridged() << ")" << "</div>";
diff --git a/ethminer/MinerAux.h b/ethminer/MinerAux.h
index ff28132b1..5c6112743 100644
--- a/ethminer/MinerAux.h
+++ b/ethminer/MinerAux.h
@@ -254,17 +254,17 @@ public:
 				bi.difficulty = u256(m);
 				auto boundary = bi.boundary();
 				m = boost::to_lower_copy(string(argv[++i]));
-				bi.nonce = h64(m);
-				auto r = EthashAux::eval(seedHash, powHash, bi.nonce);
+				bi.proof.nonce = h64(m);
+				auto r = EthashAux::eval(seedHash, powHash, bi.proof.nonce);
 				bool valid = r.value < boundary;
 				cout << (valid ? "VALID :-)" : "INVALID :-(") << endl;
 				cout << r.value << (valid ? " < " : " >= ") << boundary << endl;
 				cout << "  where " << boundary << " = 2^256 / " << bi.difficulty << endl;
-				cout << "  and " << r.value << " = ethash(" << powHash << ", " << bi.nonce << ")" << endl;
+				cout << "  and " << r.value << " = ethash(" << powHash << ", " << bi.proof.nonce << ")" << endl;
 				cout << "  with seed as " << seedHash << endl;
 				if (valid)
 					cout << "(mixHash = " << r.mixHash << ")" << endl;
-				cout << "SHA3( light(seed) ) = " << sha3(EthashAux::light(bi.seedHash())->data()) << endl;
+				cout << "SHA3( light(seed) ) = " << sha3(EthashAux::light(bi.proofCache())->data()) << endl;
 				exit(0);
 			}
 			catch (...)
@@ -382,7 +382,7 @@ private:
 	{
 		BlockInfo bi;
 		bi.number = _n;
-		cout << "Initializing DAG for epoch beginning #" << (bi.number / 30000 * 30000) << " (seedhash " << bi.seedHash().abridged() << "). This will take a while." << endl;
+		cout << "Initializing DAG for epoch beginning #" << (bi.number / 30000 * 30000) << " (seedhash " << bi.proofCache().abridged() << "). This will take a while." << endl;
 		Ethash::prep(bi);
 		exit(0);
 	}
diff --git a/exp/main.cpp b/exp/main.cpp
index 88608f8cf..9884bd0e1 100644
--- a/exp/main.cpp
+++ b/exp/main.cpp
@@ -197,7 +197,7 @@ int main()
 		bool completed = false;
 		f.onSolutionFound([&](ProofOfWork::Solution sol)
 		{
-			ProofOfWork::assignResult(sol, bi);
+			bi.proof = sol;
 			return completed = true;
 		});
 		f.setWork(bi);
diff --git a/libethcore/BlockInfo.cpp b/libethcore/BlockInfo.cpp
index fec5b4678..c7acd9091 100644
--- a/libethcore/BlockInfo.cpp
+++ b/libethcore/BlockInfo.cpp
@@ -26,7 +26,6 @@
 #include <libethcore/Common.h>
 #include <libethcore/Params.h>
 #include "EthashAux.h"
-#include "ProofOfWork.h"
 #include "Exceptions.h"
 #include "BlockInfo.h"
 using namespace std;
@@ -57,22 +56,21 @@ void BlockInfo::clear()
 	gasUsed = 0;
 	timestamp = 0;
 	extraData.clear();
-	mixHash = h256();
-	nonce = Nonce();
-	m_hash = m_seedHash = h256();
+	proof = ProofOfWork::Solution();
+	m_proofCache = ProofOfWork::HeaderCache();
+	m_hash = h256();
 }
 
-h256 const& BlockInfo::seedHash() const
+ProofOfWork::HeaderCache const& BlockInfo::proofCache() const
 {
-	if (!m_seedHash)
-		m_seedHash = EthashAux::seedHash((unsigned)number);
-	return m_seedHash;
+	ProofOfWork::ensureHeaderCacheValid(m_proofCache, *this);
+	return m_proofCache;
 }
 
 h256 const& BlockInfo::hash() const
 {
 	if (!m_hash)
-		m_hash = headerHash(WithNonce);
+		m_hash = headerHash(WithProof);
 	return m_hash;
 }
 
@@ -90,20 +88,20 @@ BlockInfo BlockInfo::fromHeader(bytesConstRef _header, Strictness _s, h256 const
 	return ret;
 }
 
-h256 BlockInfo::headerHash(IncludeNonce _n) const
+h256 BlockInfo::headerHash(IncludeProof _n) const
 {
 	RLPStream s;
 	streamRLP(s, _n);
 	return sha3(s.out());
 }
 
-void BlockInfo::streamRLP(RLPStream& _s, IncludeNonce _n) const
+void BlockInfo::streamRLP(RLPStream& _s, IncludeProof _n) const
 {
-	_s.appendList(_n == WithNonce ? 15 : 13)
+	_s.appendList(_n == WithProof ? 13 + ProofOfWork::Solution::Fields : 13)
 		<< parentHash << sha3Uncles << coinbaseAddress << stateRoot << transactionsRoot << receiptsRoot << logBloom
 		<< difficulty << number << gasLimit << gasUsed << timestamp << extraData;
-	if (_n == WithNonce)
-		_s << mixHash << nonce;
+	if (_n == WithProof)
+		proof.streamRLP(_s);
 }
 
 h256 BlockInfo::headerHash(bytesConstRef _block)
@@ -116,12 +114,12 @@ void BlockInfo::populateFromHeader(RLP const& _header, Strictness _s, h256 const
 	m_hash = _h;
 	if (_h)
 		assert(_h == dev::sha3(_header.data()));
-	m_seedHash = h256();
+	m_proofCache = ProofOfWork::HeaderCache();
 
 	int field = 0;
 	try
 	{
-		if (_header.itemCount() != 15)
+		if (_header.itemCount() != 13 + ProofOfWork::Solution::Fields)
 			BOOST_THROW_EXCEPTION(InvalidBlockHeaderItemCount());
 		parentHash = _header[field = 0].toHash<h256>(RLP::VeryStrict);
 		sha3Uncles = _header[field = 1].toHash<h256>(RLP::VeryStrict);
@@ -136,8 +134,7 @@ void BlockInfo::populateFromHeader(RLP const& _header, Strictness _s, h256 const
 		gasUsed = _header[field = 10].toInt<u256>();
 		timestamp = _header[field = 11].toInt<u256>();
 		extraData = _header[field = 12].toBytes();
-		mixHash = _header[field = 13].toHash<h256>(RLP::VeryStrict);
-		nonce = _header[field = 14].toHash<Nonce>(RLP::VeryStrict);
+		proof.populateFromRLP(_header, field = 13);
 	}
 	catch (Exception const& _e)
 	{
@@ -152,22 +149,18 @@ void BlockInfo::populateFromHeader(RLP const& _header, Strictness _s, h256 const
 	if (_s == CheckEverything && parentHash && !ProofOfWork::verify(*this))
 	{
 		InvalidBlockNonce ex;
-		ex << errinfo_hash256(headerHash(WithoutNonce));
-		ex << errinfo_nonce(nonce);
+		ProofOfWork::composeException(ex, *this);
+		ex << errinfo_hash256(headerHash(WithoutProof));
 		ex << errinfo_difficulty(difficulty);
-		ex << errinfo_seedHash(seedHash());
 		ex << errinfo_target(boundary());
-		ex << errinfo_mixHash(mixHash);
-		Ethash::Result er = EthashAux::eval(seedHash(), headerHash(WithoutNonce), nonce);
-		ex << errinfo_ethashResult(make_tuple(er.value, er.mixHash));
 		BOOST_THROW_EXCEPTION(ex);
 	}
 	else if (_s == QuickNonce && parentHash && !ProofOfWork::preVerify(*this))
 	{
 		InvalidBlockNonce ex;
-		ex << errinfo_hash256(headerHash(WithoutNonce));
-		ex << errinfo_nonce(nonce);
+		ex << errinfo_hash256(headerHash(WithoutProof));
 		ex << errinfo_difficulty(difficulty);
+		ProofOfWork::composeExceptionPre(ex, *this);
 		BOOST_THROW_EXCEPTION(ex);
 	}
 
diff --git a/libethcore/BlockInfo.h b/libethcore/BlockInfo.h
index 79c12ebb4..b77c47c6b 100644
--- a/libethcore/BlockInfo.h
+++ b/libethcore/BlockInfo.h
@@ -24,16 +24,17 @@
 #include <libdevcore/Common.h>
 #include <libdevcore/RLP.h>
 #include "Common.h"
+#include "ProofOfWork.h"
 
 namespace dev
 {
 namespace eth
 {
 
-enum IncludeNonce
+enum IncludeProof
 {
-	WithoutNonce = 0,
-	WithNonce = 1
+	WithoutProof = 0,
+	WithProof = 1
 };
 
 enum Strictness
@@ -82,8 +83,7 @@ public:
 	u256 gasUsed;
 	u256 timestamp = Invalid256;
 	bytes extraData;
-	h256 mixHash;
-	Nonce nonce;
+	typename ProofOfWork::Solution proof;
 
 	BlockInfo();
 	explicit BlockInfo(bytes const& _block, Strictness _s = IgnoreNonce, h256 const& _h = h256()): BlockInfo(&_block, _s, _h) {}
@@ -112,14 +112,13 @@ public:
 			gasUsed == _cmp.gasUsed &&
 			timestamp == _cmp.timestamp &&
 			extraData == _cmp.extraData &&
-			mixHash == _cmp.mixHash &&
-			nonce == _cmp.nonce;
+			proof == _cmp.proof;
 	}
 	bool operator!=(BlockInfo const& _cmp) const { return !operator==(_cmp); }
 
 	void clear();
 
-	void noteDirty() const { m_hash = m_seedHash = m_boundary = h256(); }
+	void noteDirty() const { m_hash = m_boundary = h256(); m_proofCache = ProofOfWork::HeaderCache(); }
 
 	void populateFromHeader(RLP const& _header, Strictness _s = IgnoreNonce, h256 const& _h = h256());
 	void populate(bytesConstRef _block, Strictness _s = IgnoreNonce, h256 const& _h = h256());
@@ -130,16 +129,17 @@ public:
 
 	u256 calculateDifficulty(BlockInfo const& _parent) const;
 	u256 selectGasLimit(BlockInfo const& _parent) const;
-	h256 const& seedHash() const;
+	ProofOfWork::HeaderCache const& proofCache() const;
 	h256 const& hash() const;
 	h256 const& boundary() const;
 
 	/// sha3 of the header only.
-	h256 headerHash(IncludeNonce _n) const;
-	void streamRLP(RLPStream& _s, IncludeNonce _n) const;
+	h256 headerHash(IncludeProof _n) const;
+	void streamRLP(RLPStream& _s, IncludeProof _n) const;
 
 private:
-	mutable h256 m_seedHash;
+
+	mutable ProofOfWork::HeaderCache m_proofCache;
 	mutable h256 m_hash;						///< SHA3 hash of the block header! Not serialised.
 	mutable h256 m_boundary;					///< 2^256 / difficulty
 };
@@ -148,7 +148,7 @@ inline std::ostream& operator<<(std::ostream& _out, BlockInfo const& _bi)
 {
 	_out << _bi.hash() << " " << _bi.parentHash << " " << _bi.sha3Uncles << " " << _bi.coinbaseAddress << " " << _bi.stateRoot << " " << _bi.transactionsRoot << " " <<
 			_bi.receiptsRoot << " " << _bi.logBloom << " " << _bi.difficulty << " " << _bi.number << " " << _bi.gasLimit << " " <<
-			_bi.gasUsed << " " << _bi.timestamp << " " << _bi.mixHash << " " << _bi.nonce << " (" << _bi.seedHash() << ")";
+			_bi.gasUsed << " " << _bi.timestamp;
 	return _out;
 }
 
diff --git a/libethcore/Common.cpp b/libethcore/Common.cpp
index 618703e22..41cd1bba8 100644
--- a/libethcore/Common.cpp
+++ b/libethcore/Common.cpp
@@ -26,6 +26,7 @@
 #include <libdevcore/SHA3.h>
 #include "Exceptions.h"
 #include "ProofOfWork.h"
+#include "BlockInfo.h"
 using namespace std;
 using namespace dev;
 using namespace dev::eth;
@@ -112,9 +113,9 @@ std::string formatBalance(bigint const& _b)
 
 static void badBlockInfo(BlockInfo const& _bi, string const& _err)
 {
-	string const c_line = EthReset EthOnMaroon + string(80, ' ');
+	string const c_line = EthReset EthOnMaroon + string(80, ' ') + EthReset;
 	string const c_border = EthReset EthOnMaroon + string(2, ' ') + EthReset EthMaroonBold;
-	string const c_space = c_border + string(76, ' ') + c_border;
+	string const c_space = c_border + string(76, ' ') + c_border + EthReset;
 	stringstream ss;
 	ss << c_line << endl;
 	ss << c_space << endl;
diff --git a/libethcore/Common.h b/libethcore/Common.h
index 296f0d01d..1e0cdc3b1 100644
--- a/libethcore/Common.h
+++ b/libethcore/Common.h
@@ -189,6 +189,7 @@ struct TransactionSkeleton
 	Address to;
 	u256 value;
 	bytes data;
+	u256 nonce = UndefinedU256;
 	u256 gas = UndefinedU256;
 	u256 gasPrice = UndefinedU256;
 	u256 nonce = UndefinedU256;
diff --git a/libethcore/Ethash.cpp b/libethcore/Ethash.cpp
index 9be76926d..6a4a1445f 100644
--- a/libethcore/Ethash.cpp
+++ b/libethcore/Ethash.cpp
@@ -46,6 +46,7 @@
 #endif
 #include "BlockInfo.h"
 #include "EthashAux.h"
+#include "Exceptions.h"
 using namespace std;
 using namespace std::chrono;
 
@@ -56,6 +57,26 @@ namespace eth
 
 const Ethash::WorkPackage Ethash::NullWorkPackage = Ethash::WorkPackage();
 
+void Ethash::ensureHeaderCacheValid(HeaderCache& io_out, BlockInfo const& _h)
+{
+	if (!io_out)
+		io_out = EthashAux::seedHash((unsigned)_h.number);
+}
+
+void Ethash::composeException(Exception& _ex, BlockInfo& _bi)
+{
+	_ex << errinfo_nonce(_bi.proof.nonce);
+	_ex << errinfo_mixHash(_bi.proof.mixHash);
+	_ex << errinfo_seedHash(_bi.proofCache());
+	Ethash::Result er = EthashAux::eval(_bi.proofCache(), _bi.headerHash(WithoutProof), _bi.proof.nonce);
+	_ex << errinfo_ethashResult(make_tuple(er.value, er.mixHash));
+}
+
+void Ethash::composeExceptionPre(Exception& _ex, BlockInfo& _bi)
+{
+	_ex << errinfo_nonce(_bi.proof.nonce);
+}
+
 std::string Ethash::name()
 {
 	return "Ethash";
@@ -66,12 +87,23 @@ unsigned Ethash::revision()
 	return ETHASH_REVISION;
 }
 
+void Ethash::Solution::populateFromRLP(RLP const& _header, int& _field)
+{
+	mixHash = _header[_field].toHash<h256>(RLP::VeryStrict);
+	nonce = _header[++_field].toHash<Nonce>(RLP::VeryStrict);
+}
+
+void Ethash::Solution::streamRLP(RLPStream& io_rlp) const
+{
+	io_rlp << mixHash << nonce;
+}
+
 Ethash::WorkPackage Ethash::package(BlockInfo const& _bi)
 {
 	WorkPackage ret;
 	ret.boundary = _bi.boundary();
-	ret.headerHash = _bi.headerHash(WithoutNonce);
-	ret.seedHash = _bi.seedHash();
+	ret.headerHash = _bi.headerHash(WithoutProof);
+	ret.seedHash = _bi.proofCache();
 	return ret;
 }
 
@@ -84,7 +116,7 @@ void Ethash::ensurePrecomputed(unsigned _number)
 
 void Ethash::prep(BlockInfo const& _header, std::function<int(unsigned)> const& _f)
 {
-	EthashAux::full(_header.seedHash(), true, _f);
+	EthashAux::full(_header.proofCache(), true, _f);
 }
 
 bool Ethash::preVerify(BlockInfo const& _header)
@@ -95,9 +127,9 @@ bool Ethash::preVerify(BlockInfo const& _header)
 	h256 boundary = u256((bigint(1) << 256) / _header.difficulty);
 
 	bool ret = !!ethash_quick_check_difficulty(
-			(ethash_h256_t const*)_header.headerHash(WithoutNonce).data(),
-			(uint64_t)(u64)_header.nonce,
-			(ethash_h256_t const*)_header.mixHash.data(),
+			(ethash_h256_t const*)_header.headerHash(WithoutProof).data(),
+			(uint64_t)(u64)_header.proof.nonce,
+			(ethash_h256_t const*)_header.proof.mixHash.data(),
 			(ethash_h256_t const*)boundary.data());
 
 	return ret;
@@ -115,7 +147,7 @@ bool Ethash::verify(BlockInfo const& _header)
 #endif
 
 	auto result = EthashAux::eval(_header);
-	bool slow = result.value <= _header.boundary() && result.mixHash == _header.mixHash;
+	bool slow = result.value <= _header.boundary() && result.mixHash == _header.proof.mixHash;
 
 //	cdebug << (slow ? "VERIFY" : "VERYBAD");
 //	cdebug << result.value.hex() << _header.boundary().hex();
@@ -125,9 +157,9 @@ bool Ethash::verify(BlockInfo const& _header)
 	if (!pre && slow)
 	{
 		cwarn << "WARNING: evaluated result gives true whereas ethash_quick_check_difficulty gives false.";
-		cwarn << "headerHash:" << _header.headerHash(WithoutNonce);
-		cwarn << "nonce:" << _header.nonce;
-		cwarn << "mixHash:" << _header.mixHash;
+		cwarn << "headerHash:" << _header.headerHash(WithoutProof);
+		cwarn << "nonce:" << _header.proof.nonce;
+		cwarn << "mixHash:" << _header.proof.mixHash;
 		cwarn << "difficulty:" << _header.difficulty;
 		cwarn << "boundary:" << _header.boundary();
 		cwarn << "result.value:" << result.value;
diff --git a/libethcore/Ethash.h b/libethcore/Ethash.h
index 7ffd887d0..5640152f0 100644
--- a/libethcore/Ethash.h
+++ b/libethcore/Ethash.h
@@ -28,16 +28,20 @@
 #include <cstdint>
 #include <libdevcore/CommonIO.h>
 #include "Common.h"
-#include "BlockInfo.h"
 #include "Miner.h"
 
 class ethash_cl_miner;
 
 namespace dev
 {
+
+class RLP;
+class RLPStream;
+
 namespace eth
 {
 
+class BlockInfo;
 class EthashCLHook;
 
 class Ethash
@@ -45,8 +49,17 @@ class Ethash
 public:
 	using Miner = GenericMiner<Ethash>;
 
+	using HeaderCache = h256;
+	static void ensureHeaderCacheValid(HeaderCache& io_out, BlockInfo const& _h);
+	static void composeException(Exception& _ex, BlockInfo& _bi);
+	static void composeExceptionPre(Exception& _ex, BlockInfo& _bi);
+
 	struct Solution
 	{
+		bool operator==(Solution const& _v) const { return nonce == _v.nonce && mixHash == _v.mixHash; }
+		void populateFromRLP(RLP const& io_rlp, int& io_field);
+		void streamRLP(RLPStream& io_rlp) const;
+		static const unsigned Fields = 2;
 		Nonce nonce;
 		h256 mixHash;
 	};
@@ -78,7 +91,6 @@ public:
 	static bool verify(BlockInfo const& _header);
 	static bool preVerify(BlockInfo const& _header);
 	static WorkPackage package(BlockInfo const& _header);
-	static void assignResult(Solution const& _r, BlockInfo& _header) { _header.nonce = _r.nonce; _header.mixHash = _r.mixHash; }
 
 	class CPUMiner: public Miner, Worker
 	{
diff --git a/libethcore/EthashAux.cpp b/libethcore/EthashAux.cpp
index efb6066f7..db01f3c49 100644
--- a/libethcore/EthashAux.cpp
+++ b/libethcore/EthashAux.cpp
@@ -200,6 +200,11 @@ EthashAux::FullType EthashAux::full(h256 const& _seedHash, bool _createIfMissing
 	return ret;
 }
 
+Ethash::Result EthashAux::eval(BlockInfo const& _header)
+{
+	return eval(_header, _header.proof.nonce);
+}
+
 #define DEV_IF_THROWS(X) try { X; } catch (...)
 
 unsigned EthashAux::computeFull(h256 const& _seedHash, bool _createIfMissing)
@@ -252,7 +257,7 @@ Ethash::Result EthashAux::LightAllocation::compute(h256 const& _headerHash, Nonc
 
 Ethash::Result EthashAux::eval(BlockInfo const& _header, Nonce const& _nonce)
 {
-	return eval(_header.seedHash(), _header.headerHash(WithoutNonce), _nonce);
+	return eval(_header.proofCache(), _header.headerHash(WithoutProof), _nonce);
 }
 
 Ethash::Result EthashAux::eval(h256 const& _seedHash, h256 const& _headerHash, Nonce const& _nonce)
diff --git a/libethcore/EthashAux.h b/libethcore/EthashAux.h
index d5bd60d44..be07f579c 100644
--- a/libethcore/EthashAux.h
+++ b/libethcore/EthashAux.h
@@ -78,7 +78,7 @@ public:
 	/// Kicks off generation of DAG for @a _blocknumber and blocks until ready; @returns result or empty pointer if not existing and _createIfMissing is false.
 	static FullType full(h256 const& _seedHash, bool _createIfMissing = false, std::function<int(unsigned)> const& _f = std::function<int(unsigned)>());
 
-	static Ethash::Result eval(BlockInfo const& _header) { return eval(_header, _header.nonce); }
+	static Ethash::Result eval(BlockInfo const& _header);
 	static Ethash::Result eval(BlockInfo const& _header, Nonce const& _nonce);
 	static Ethash::Result eval(h256 const& _seedHash, h256 const& _headerHash, Nonce const& _nonce);
 
diff --git a/libethcore/ProofOfWork.h b/libethcore/ProofOfWork.h
index 764207aef..7b4298047 100644
--- a/libethcore/ProofOfWork.h
+++ b/libethcore/ProofOfWork.h
@@ -38,7 +38,6 @@ namespace eth
  * typename Solution
  * typename CPUMiner
  * typename GPUMiner
- * void assignResult(BlockInfo&, Result)
  * and a few others. TODO
  */
 using ProofOfWork = Ethash;
diff --git a/libethereum/BlockChain.cpp b/libethereum/BlockChain.cpp
index 768ed223f..aaafe7ce9 100644
--- a/libethereum/BlockChain.cpp
+++ b/libethereum/BlockChain.cpp
@@ -575,8 +575,8 @@ ImportRoute BlockChain::import(VerifiedBlockRef const& _block, OverlayDB const&
 #endif
 
 	StructuredLogger::chainReceivedNewBlock(
-		_block.info.headerHash(WithoutNonce).abridged(),
-		_block.info.nonce.abridged(),
+		_block.info.headerHash(WithoutProof).abridged(),
+		_block.info.proof.nonce.abridged(),
 		currentHash().abridged(),
 		"", // TODO: remote id ??
 		_block.info.parentHash.abridged()
@@ -666,8 +666,8 @@ ImportRoute BlockChain::import(VerifiedBlockRef const& _block, OverlayDB const&
 		clog(BlockChainNote) << "   Imported and best" << td << " (#" << _block.info.number << "). Has" << (details(_block.info.parentHash).children.size() - 1) << "siblings. Route:" << route;
 
 		StructuredLogger::chainNewHead(
-			_block.info.headerHash(WithoutNonce).abridged(),
-			_block.info.nonce.abridged(),
+			_block.info.headerHash(WithoutProof).abridged(),
+			_block.info.proof.nonce.abridged(),
 			currentHash().abridged(),
 			_block.info.parentHash.abridged()
 		);
diff --git a/libethereum/BlockQueue.cpp b/libethereum/BlockQueue.cpp
index f95a3880e..690fb60ee 100644
--- a/libethereum/BlockQueue.cpp
+++ b/libethereum/BlockQueue.cpp
@@ -101,7 +101,7 @@ void BlockQueue::verifierBody()
 			swap(work, m_unverified.front());
 			m_unverified.pop_front();
 			BlockInfo bi;
-			bi.mixHash = work.hash;
+			bi.proof.mixHash = work.hash;
 			bi.parentHash = work.parentHash;
 			m_verifying.emplace_back(move(bi));
 		}
@@ -121,7 +121,7 @@ void BlockQueue::verifierBody()
 			m_readySet.erase(work.hash);
 			m_knownBad.insert(work.hash);
 			for (auto it = m_verifying.begin(); it != m_verifying.end(); ++it)
-				if (it->verified.info.mixHash == work.hash)
+				if (it->verified.info.proof.mixHash == work.hash)
 				{
 					m_verifying.erase(it);
 					goto OK1;
@@ -136,7 +136,7 @@ void BlockQueue::verifierBody()
 		{
 			WriteGuard l2(m_lock);
 			unique_lock<Mutex> l(m_verification);
-			if (!m_verifying.empty() && m_verifying.front().verified.info.mixHash == work.hash)
+			if (!m_verifying.empty() && m_verifying.front().verified.info.proof.mixHash == work.hash)
 			{
 				// we're next!
 				m_verifying.pop_front();
@@ -154,7 +154,7 @@ void BlockQueue::verifierBody()
 			else
 			{
 				for (auto& i: m_verifying)
-					if (i.verified.info.mixHash == work.hash)
+					if (i.verified.info.proof.mixHash == work.hash)
 					{
 						i = move(res);
 						goto OK;
@@ -323,9 +323,9 @@ void BlockQueue::updateBad_WITH_LOCK(h256 const& _bad)
 			std::deque<VerifiedBlock> oldVerifying;
 			swap(m_verifying, oldVerifying);
 			for (auto& b: oldVerifying)
-				if (m_knownBad.count(b.verified.info.parentHash) || m_knownBad.count(b.verified.info.mixHash))
+				if (m_knownBad.count(b.verified.info.parentHash) || m_knownBad.count(b.verified.info.proof.mixHash))
 				{
-					h256 const& h = b.blockData.size() != 0 ? b.verified.info.hash() : b.verified.info.mixHash;
+					h256 const& h = b.blockData.size() != 0 ? b.verified.info.hash() : b.verified.info.proof.mixHash;
 					m_knownBad.insert(h);
 					m_readySet.erase(h);
 					collectUnknownBad_WITH_BOTH_LOCKS(h);
diff --git a/libethereum/State.cpp b/libethereum/State.cpp
index 10d637509..bf55a50ff 100644
--- a/libethereum/State.cpp
+++ b/libethereum/State.cpp
@@ -837,7 +837,7 @@ bool State::amIJustParanoid(BlockChain const& _bc)
 	// Compile block:
 	RLPStream block;
 	block.appendList(3);
-	m_currentBlock.streamRLP(block, WithNonce);
+	m_currentBlock.streamRLP(block, WithProof);
 	block.appendRaw(m_currentTxs);
 	block.appendRaw(m_currentUncles);
 
@@ -902,7 +902,7 @@ void State::commitToMine(BlockChain const& _bc, bytes const& _extraData)
 				if (!excluded.count(u))	// ignore any uncles/mainline blocks that we know about.
 				{
 					BlockInfo ubi(_bc.block(u));
-					ubi.streamRLP(unclesData, WithNonce);
+					ubi.streamRLP(unclesData, WithProof);
 					++unclesCount;
 					uncleBlockHeaders.push_back(ubi);
 					if (unclesCount == 2)
@@ -970,7 +970,7 @@ void State::completeMine()
 	// Compile block:
 	RLPStream ret;
 	ret.appendList(3);
-	m_currentBlock.streamRLP(ret, WithNonce);
+	m_currentBlock.streamRLP(ret, WithProof);
 	ret.appendRaw(m_currentTxs);
 	ret.appendRaw(m_currentUncles);
 	ret.swapOut(m_currentBytes);
@@ -978,7 +978,7 @@ void State::completeMine()
 	cnote << "Mined " << m_currentBlock.hash() << "(parent: " << m_currentBlock.parentHash << ")";
 	StructuredLogger::minedNewBlock(
 		m_currentBlock.hash().abridged(),
-		m_currentBlock.nonce.abridged(),
+		m_currentBlock.proof.nonce.abridged(),
 		"", //TODO: chain head hash here ??
 		m_currentBlock.parentHash.abridged()
 	);
diff --git a/libethereum/State.h b/libethereum/State.h
index ef8a3251a..0555b6dcd 100644
--- a/libethereum/State.h
+++ b/libethereum/State.h
@@ -169,11 +169,11 @@ public:
 		if (!m_committedToMine)
 			return false;
 
-		PoW::assignResult(_result, m_currentBlock);
+		m_currentBlock.proof = _result;
 		if (!PoW::verify(m_currentBlock))
 			return false;
 
-		cnote << "Completed" << m_currentBlock.headerHash(WithoutNonce) << m_currentBlock.nonce << m_currentBlock.difficulty << PoW::verify(m_currentBlock);
+		cnote << "Completed" << m_currentBlock.headerHash(WithoutProof) << m_currentBlock.proof.nonce << m_currentBlock.difficulty << PoW::verify(m_currentBlock);
 
 		completeMine();
 
diff --git a/libweb3jsonrpc/JsonHelper.cpp b/libweb3jsonrpc/JsonHelper.cpp
index 96312f625..f7c09ebc2 100644
--- a/libweb3jsonrpc/JsonHelper.cpp
+++ b/libweb3jsonrpc/JsonHelper.cpp
@@ -99,11 +99,12 @@ Json::Value toJson(dev::eth::BlockInfo const& _bi)
 		res["gasLimit"] = toJS(_bi.gasLimit);
 		res["timestamp"] = toJS(_bi.timestamp);
 		res["extraData"] = toJS(_bi.extraData);
-		res["nonce"] = toJS(_bi.nonce);
 		res["logsBloom"] = toJS(_bi.logBloom);
-
-		res["seedHash"] = toJS(_bi.seedHash());
 		res["target"] = toJS(_bi.boundary());
+
+		// TODO: move into ProofOfWork.
+		res["nonce"] = toJS(_bi.proof.nonce);
+		res["seedHash"] = toJS(_bi.proofCache());
 	}
 	return res;
 }
diff --git a/mix/MixClient.cpp b/mix/MixClient.cpp
index 8373c7c51..ea4686601 100644
--- a/mix/MixClient.cpp
+++ b/mix/MixClient.cpp
@@ -49,7 +49,6 @@ namespace
 struct MixPow //dummy POW
 {
 	typedef int Solution;
-	static void assignResult(int, BlockInfo const&) {}
 	static bool verify(BlockInfo const&) { return true; }
 };
 
diff --git a/test/TestHelper.cpp b/test/TestHelper.cpp
index f49ed1e09..b43c4db51 100644
--- a/test/TestHelper.cpp
+++ b/test/TestHelper.cpp
@@ -81,7 +81,7 @@ void mine(BlockInfo& _bi)
 	bool completed = false;
 	f.onSolutionFound([&](ProofOfWork::Solution sol)
 	{
-		ProofOfWork::assignResult(sol, _bi);
+		_bi.proof = sol;
 		return completed = true;
 	});
 	f.setWork(_bi);