diff --git a/eth/main.cpp b/eth/main.cpp
index 67058a473..1e724c7e6 100644
--- a/eth/main.cpp
+++ b/eth/main.cpp
@@ -1702,7 +1702,10 @@ int main(int argc, char** argv)
 	{
 		c->setGasPricer(gasPricer);
 		c->setForceMining(forceMining);
+		// TODO: expose sealant interface.
+#if ETH_USING_ETHASH
 		c->setTurboMining(m.minerType() == MinerCLI::MinerType::GPU);
+#endif
 		c->setAddress(beneficiary);
 		c->setNetworkId(networkId);
 	}
diff --git a/ethminer/MinerAux.h b/ethminer/MinerAux.h
index 5c6112743..051128669 100644
--- a/ethminer/MinerAux.h
+++ b/ethminer/MinerAux.h
@@ -99,10 +99,16 @@ public:
 		Farm
 	};
 
+
+#if ETH_USING_ETHASH
 	MinerCLI(OperationMode _mode = OperationMode::None): mode(_mode) {}
+#else
+	MinerCLI(OperationMode = OperationMode::None) {}
+#endif
 
 	bool interpretOption(int& i, int argc, char** argv)
 	{
+#if ETH_USING_ETHASH
 		string arg = argv[i];
 		if ((arg == "-F" || arg == "--farm") && i + 1 < argc)
 		{
@@ -289,22 +295,29 @@ public:
 		else
 			return false;
 		return true;
+#else
+		(void)i;
+		(void)argc;
+		(void)argv;
+		return false;
+#endif
 	}
 
 	void execute()
 	{
+#if ETH_USING_ETHASH
 		if (m_shouldListDevices)
 		{
-			ProofOfWork::GPUMiner::listDevices();
+			Ethash::GPUMiner::listDevices();
 			exit(0);
 		}
 
 		if (m_minerType == MinerType::CPU)
-			ProofOfWork::CPUMiner::setNumInstances(m_miningThreads);
+			Ethash::CPUMiner::setNumInstances(m_miningThreads);
 		else if (m_minerType == MinerType::GPU)
 		{
 #if ETH_ETHASHCL || !ETH_TRUE
-			if (!ProofOfWork::GPUMiner::configureGPU(
+			if (!Ethash::GPUMiner::configureGPU(
 					m_localWorkSize,
 					m_globalWorkSizeMultiplier,
 					m_msPerBatch,
@@ -315,7 +328,7 @@ public:
 					m_currentBlock
 				))
 				exit(1);
-			ProofOfWork::GPUMiner::setNumInstances(m_miningThreads);
+			Ethash::GPUMiner::setNumInstances(m_miningThreads);
 #else
 			cerr << "Selected GPU mining without having compiled with -DETHASHCL=1" << endl;
 			exit(1);
@@ -327,10 +340,12 @@ public:
 			doBenchmark(m_minerType, m_phoneHome, m_benchmarkWarmup, m_benchmarkTrial, m_benchmarkTrials);
 		else if (mode == OperationMode::Farm)
 			doFarm(m_minerType, m_farmURL, m_farmRecheckPeriod);
+#endif
 	}
 
 	static void streamHelp(ostream& _out)
 	{
+#if ETH_USING_ETHASH
 		_out
 #if ETH_JSONRPC || !ETH_TRUE
 			<< "Work farming mode:" << endl
@@ -367,8 +382,12 @@ public:
 			<< "    --cl-ms-per-batch Set the OpenCL target milliseconds per batch (global workgroup size). Default is " << toString(ethash_cl_miner::c_defaultMSPerBatch) << ". If 0 is given then no autoadjustment of global work size will happen" << endl
 #endif
 			;
+#else
+		(void)_out;
+#endif
 	}
 
+#if ETH_USING_ETHASH
 	enum class MinerType
 	{
 		CPU,
@@ -576,4 +595,5 @@ private:
 	string m_farmURL = "http://127.0.0.1:8545";
 	unsigned m_farmRecheckPeriod = 500;
 	bool m_precompute = true;
+#endif
 };
diff --git a/libdevcrypto/Common.cpp b/libdevcrypto/Common.cpp
index 186c6ce06..d64de835c 100644
--- a/libdevcrypto/Common.cpp
+++ b/libdevcrypto/Common.cpp
@@ -63,6 +63,11 @@ bool dev::SignatureStruct::isValid() const noexcept
 	return true;
 }
 
+Public SignatureStruct::recover(h256 const& _hash) const
+{
+	return dev::recover((Signature)*this, _hash);
+}
+
 Address dev::ZeroAddress = Address();
 
 Public dev::toPublic(Secret const& _secret)
diff --git a/libdevcrypto/Common.h b/libdevcrypto/Common.h
index c45e060b2..9aeb85a4c 100644
--- a/libdevcrypto/Common.h
+++ b/libdevcrypto/Common.h
@@ -54,6 +54,9 @@ struct SignatureStruct
 	/// @returns true if r,s,v values are valid, otherwise false
 	bool isValid() const noexcept;
 
+	/// @returns the public part of the key that signed @a _hash to give this sig.
+	Public recover(h256 const& _hash) const;
+
 	h256 r;
 	h256 s;
 	byte v = 0;
diff --git a/libethcore/Common.cpp b/libethcore/Common.cpp
index 41cd1bba8..58e506b37 100644
--- a/libethcore/Common.cpp
+++ b/libethcore/Common.cpp
@@ -23,6 +23,10 @@
 #include <random>
 #include <boost/algorithm/string/case_conv.hpp>
 #include <libdevcore/Base64.h>
+#include <libdevcore/Terminal.h>
+#include <libdevcore/CommonData.h>
+#include <libdevcore/CommonIO.h>
+#include <libdevcore/Log.h>
 #include <libdevcore/SHA3.h>
 #include "Exceptions.h"
 #include "ProofOfWork.h"
diff --git a/libethcore/Common.h b/libethcore/Common.h
index 1e0cdc3b1..1a688fbd8 100644
--- a/libethcore/Common.h
+++ b/libethcore/Common.h
@@ -192,11 +192,22 @@ struct TransactionSkeleton
 	u256 nonce = UndefinedU256;
 	u256 gas = UndefinedU256;
 	u256 gasPrice = UndefinedU256;
-	u256 nonce = UndefinedU256;
 };
 
 void badBlock(bytesConstRef _header, std::string const& _err);
 inline void badBlock(bytes const& _header, std::string const& _err) { badBlock(&_header, _err); }
 
+// TODO: move back into a mining subsystem and have it be accessible from Sealant only via a dynamic_cast.
+/**
+ * @brief Describes the progress of a mining operation.
+ */
+struct MiningProgress
+{
+//	MiningProgress& operator+=(MiningProgress const& _mp) { hashes += _mp.hashes; ms = std::max(ms, _mp.ms); return *this; }
+	uint64_t hashes = 0;		///< Total number of hashes computed.
+	uint64_t ms = 0;			///< Total number of milliseconds of mining thus far.
+	uint64_t rate() const { return ms == 0 ? 0 : hashes * 1000 / ms; }
+};
+
 }
 }
diff --git a/libethcore/Ethash.cpp b/libethcore/Ethash.cpp
index 6a4a1445f..c08f26ca9 100644
--- a/libethcore/Ethash.cpp
+++ b/libethcore/Ethash.cpp
@@ -65,16 +65,26 @@ void Ethash::ensureHeaderCacheValid(HeaderCache& io_out, BlockInfo const& _h)
 
 void Ethash::composeException(Exception& _ex, BlockInfo& _bi)
 {
+#if ETH_USING_ETHASH
 	_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));
+#else
+	(void)_ex;
+	(void)_bi;
+#endif
 }
 
 void Ethash::composeExceptionPre(Exception& _ex, BlockInfo& _bi)
 {
+#if ETH_USING_ETHASH
 	_ex << errinfo_nonce(_bi.proof.nonce);
+#else
+	(void)_ex;
+	(void)_bi;
+#endif
 }
 
 std::string Ethash::name()
@@ -103,7 +113,9 @@ Ethash::WorkPackage Ethash::package(BlockInfo const& _bi)
 	WorkPackage ret;
 	ret.boundary = _bi.boundary();
 	ret.headerHash = _bi.headerHash(WithoutProof);
+#if ETH_USING_ETHASH
 	ret.seedHash = _bi.proofCache();
+#endif
 	return ret;
 }
 
@@ -116,7 +128,12 @@ void Ethash::ensurePrecomputed(unsigned _number)
 
 void Ethash::prep(BlockInfo const& _header, std::function<int(unsigned)> const& _f)
 {
+#if ETH_USING_ETHASH
 	EthashAux::full(_header.proofCache(), true, _f);
+#else
+	(void)_header;
+	(void)_f;
+#endif
 }
 
 bool Ethash::preVerify(BlockInfo const& _header)
@@ -124,6 +141,7 @@ bool Ethash::preVerify(BlockInfo const& _header)
 	if (_header.number >= ETHASH_EPOCH_LENGTH * 2048)
 		return false;
 
+#if ETH_USING_ETHASH
 	h256 boundary = u256((bigint(1) << 256) / _header.difficulty);
 
 	bool ret = !!ethash_quick_check_difficulty(
@@ -131,8 +149,10 @@ bool Ethash::preVerify(BlockInfo const& _header)
 			(uint64_t)(u64)_header.proof.nonce,
 			(ethash_h256_t const*)_header.proof.mixHash.data(),
 			(ethash_h256_t const*)boundary.data());
-
 	return ret;
+#else
+	return false;
+#endif
 }
 
 bool Ethash::verify(BlockInfo const& _header)
@@ -146,6 +166,7 @@ bool Ethash::verify(BlockInfo const& _header)
 	}
 #endif
 
+#if ETH_USING_ETHASH
 	auto result = EthashAux::eval(_header);
 	bool slow = result.value <= _header.boundary() && result.mixHash == _header.proof.mixHash;
 
@@ -168,6 +189,9 @@ bool Ethash::verify(BlockInfo const& _header)
 #endif
 
 	return slow;
+#else
+	return false;
+#endif
 }
 
 unsigned Ethash::CPUMiner::s_numInstances = 0;
diff --git a/libethcore/Ethash.h b/libethcore/Ethash.h
index 5640152f0..9274e3c72 100644
--- a/libethcore/Ethash.h
+++ b/libethcore/Ethash.h
@@ -29,6 +29,7 @@
 #include <libdevcore/CommonIO.h>
 #include "Common.h"
 #include "Miner.h"
+#include "Farm.h"
 
 class ethash_cl_miner;
 
@@ -162,6 +163,36 @@ public:
 #else
 	using GPUMiner = CPUMiner;
 #endif
+	/// Default value of the local work size. Also known as workgroup size.
+	static const unsigned defaultLocalWorkSize;
+	/// Default value of the global work size as a multiplier of the local work size
+	static const unsigned defaultGlobalWorkSizeMultiplier;
+	/// Default value of the milliseconds per global work size (per batch)
+	static const unsigned defaultMSPerBatch;
+
+	struct Farm: public eth::GenericFarm<Ethash>
+	{
+	public:
+		strings sealers() const { return { "cpu", "opencl" }; }
+		void setSealer(std::string const& _sealer) { m_opencl = (_sealer == "opencl"); }
+
+		void sealBlock(BlockInfo const& _bi)
+		{
+			setWork(_bi);
+			if (m_opencl)
+				startGPU();
+			else
+				startCPU();
+
+			setWork(_bi);
+			ensurePrecomputed((unsigned)_bi.number);
+		}
+
+		void disable() { stop(); }
+
+	private:
+		bool m_opencl = false;
+	};
 };
 
 }
diff --git a/libethcore/EthashAux.cpp b/libethcore/EthashAux.cpp
index db01f3c49..42a3cf6fb 100644
--- a/libethcore/EthashAux.cpp
+++ b/libethcore/EthashAux.cpp
@@ -202,7 +202,12 @@ EthashAux::FullType EthashAux::full(h256 const& _seedHash, bool _createIfMissing
 
 Ethash::Result EthashAux::eval(BlockInfo const& _header)
 {
+#if ETH_USING_ETHASH
 	return eval(_header, _header.proof.nonce);
+#else
+	(void)_header;
+	return Ethash::Result();
+#endif
 }
 
 #define DEV_IF_THROWS(X) try { X; } catch (...)
@@ -257,7 +262,13 @@ Ethash::Result EthashAux::LightAllocation::compute(h256 const& _headerHash, Nonc
 
 Ethash::Result EthashAux::eval(BlockInfo const& _header, Nonce const& _nonce)
 {
+#if ETH_USING_ETHASH
 	return eval(_header.proofCache(), _header.headerHash(WithoutProof), _nonce);
+#else
+	(void)_header;
+	(void)_nonce;
+	return Ethash::Result();
+#endif
 }
 
 Ethash::Result EthashAux::eval(h256 const& _seedHash, h256 const& _headerHash, Nonce const& _nonce)
diff --git a/libethcore/EthashAux.h b/libethcore/EthashAux.h
index be07f579c..5ae24898d 100644
--- a/libethcore/EthashAux.h
+++ b/libethcore/EthashAux.h
@@ -23,6 +23,7 @@
 
 #include <condition_variable>
 #include <libethash/ethash.h>
+#include <libdevcore/Log.h>
 #include <libdevcore/Worker.h>
 #include "Ethash.h"
 
diff --git a/libethcore/Farm.h b/libethcore/Farm.h
index ba98becca..c43b0fab2 100644
--- a/libethcore/Farm.h
+++ b/libethcore/Farm.h
@@ -29,7 +29,6 @@
 #include <libethcore/Common.h>
 #include <libethcore/Miner.h>
 #include <libethcore/BlockInfo.h>
-#include <libethcore/ProofOfWork.h>
 
 namespace dev
 {
diff --git a/libethcore/Miner.h b/libethcore/Miner.h
index 415da9878..03eba9880 100644
--- a/libethcore/Miner.h
+++ b/libethcore/Miner.h
@@ -36,17 +36,6 @@ namespace dev
 namespace eth
 {
 
-/**
- * @brief Describes the progress of a mining operation.
- */
-struct MiningProgress
-{
-//	MiningProgress& operator+=(MiningProgress const& _mp) { hashes += _mp.hashes; ms = std::max(ms, _mp.ms); return *this; }
-	uint64_t hashes = 0;		///< Total number of hashes computed.
-	uint64_t ms = 0;			///< Total number of milliseconds of mining thus far.
-	uint64_t rate() const { return ms == 0 ? 0 : hashes * 1000 / ms; }
-};
-
 struct MineInfo: public MiningProgress {};
 
 inline std::ostream& operator<<(std::ostream& _out, MiningProgress _p)
diff --git a/libethcore/ProofOfWork.cpp b/libethcore/ProofOfWork.cpp
index ec910f7f2..bda1de0af 100644
--- a/libethcore/ProofOfWork.cpp
+++ b/libethcore/ProofOfWork.cpp
@@ -20,5 +20,30 @@
  */
 
 #include "ProofOfWork.h"
+#include "BlockInfo.h"
 using namespace std;
 using namespace dev;
+using namespace eth;
+
+const Address BasicAuthority::Authority = Address("1234567890123456789012345678901234567890");
+
+bool BasicAuthority::verify(BlockInfo const& _header)
+{
+	return toAddress(recover(_header.proof.sig, _header.headerHash(WithoutProof))) == Authority;
+}
+
+bool BasicAuthority::preVerify(BlockInfo const& _header)
+{
+	return SignatureStruct(_header.proof.sig).isValid();
+}
+
+BasicAuthority::WorkPackage BasicAuthority::package(BlockInfo const& _header)
+{
+	return WorkPackage{_header.headerHash(WithoutProof)};
+}
+
+void BasicAuthority::Farm::sealBlock(BlockInfo const& _bi)
+{
+	m_onSolutionFound(Solution{sign(m_secret, _bi.headerHash(WithoutProof))});
+}
+
diff --git a/libethcore/ProofOfWork.h b/libethcore/ProofOfWork.h
index 7b4298047..0eeed406f 100644
--- a/libethcore/ProofOfWork.h
+++ b/libethcore/ProofOfWork.h
@@ -23,13 +23,18 @@
 
 #pragma once
 
-#include "Ethash.h"
+#include <libdevcore/RLP.h>
+#include <libdevcrypto/Common.h>
+#include "Common.h"
+//#include "Ethash.h"
 
 namespace dev
 {
 namespace eth
 {
 
+class BlockInfo;
+
 /**
  * The proof of work algorithm base type.
  *
@@ -40,7 +45,74 @@ namespace eth
  * typename GPUMiner
  * and a few others. TODO
  */
-using ProofOfWork = Ethash;
+class BasicAuthority
+{
+public:
+	struct HeaderCache {};
+	static void ensureHeaderCacheValid(HeaderCache&, BlockInfo const&) {}
+	static void composeException(Exception&, BlockInfo&) {}
+	static void composeExceptionPre(Exception&, BlockInfo&) {}
+
+	struct Solution
+	{
+		bool operator==(Solution const& _v) const { return sig == _v.sig; }
+		void populateFromRLP(RLP const& io_rlp, int& io_field)
+		{
+			sig = io_rlp[io_field++].toHash<dev::Signature>(RLP::VeryStrict);
+		}
+
+		void streamRLP(RLPStream& io_rlp) const
+		{
+			io_rlp << sig;
+		}
+		static const unsigned Fields = 1;
+		Signature sig;
+	};
+
+	struct Result
+	{
+		Signature sig;
+	};
+
+	struct WorkPackage
+	{
+		void reset() { headerHash = h256(); }
+		operator bool() const { return headerHash != h256(); }
+
+		h256 headerHash;	///< When h256() means "pause until notified a new work package is available".
+	};
+
+	static const WorkPackage NullWorkPackage;
+
+	static std::string name() { return "BasicAuthority"; }
+	static unsigned revision() { return 0; }
+	static void prep(BlockInfo const&, std::function<int(unsigned)> const& = std::function<int(unsigned)>()) {}
+	static void ensurePrecomputed(unsigned) {}
+	static bool verify(BlockInfo const& _header);
+	static bool preVerify(BlockInfo const& _header);
+	static WorkPackage package(BlockInfo const& _header);
+
+	static const Address Authority;
+
+	struct Farm
+	{
+	public:
+		strings sealers() const { return { "default" }; }
+		void setSealer(std::string const&) {}
+		void setSecret(Secret const& _s) { m_secret = _s; }
+		void sealBlock(BlockInfo const& _bi);
+		void disable() {}
+		void onSolutionFound(std::function<void(Solution const& s)> const& _f) { m_onSolutionFound = _f; }
+		bool isMining() const { return false; }
+		MiningProgress miningProgress() const { return MiningProgress(); }
+
+	private:
+		Secret m_secret;
+		std::function<void(Solution const& s)> m_onSolutionFound;
+	};
+};
+
+using ProofOfWork = BasicAuthority;
 
 }
 }
diff --git a/libethereum/BlockChain.cpp b/libethereum/BlockChain.cpp
index aaafe7ce9..cf7a0905e 100644
--- a/libethereum/BlockChain.cpp
+++ b/libethereum/BlockChain.cpp
@@ -574,6 +574,7 @@ ImportRoute BlockChain::import(VerifiedBlockRef const& _block, OverlayDB const&
 	}
 #endif
 
+#if ETH_USING_ETHASH
 	StructuredLogger::chainReceivedNewBlock(
 		_block.info.headerHash(WithoutProof).abridged(),
 		_block.info.proof.nonce.abridged(),
@@ -581,6 +582,7 @@ ImportRoute BlockChain::import(VerifiedBlockRef const& _block, OverlayDB const&
 		"", // TODO: remote id ??
 		_block.info.parentHash.abridged()
 	);
+#endif
 	//	cnote << "Parent " << bi.parentHash << " has " << details(bi.parentHash).children.size() << " children.";
 
 	h256s route;
@@ -665,12 +667,14 @@ 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;
 
+#if ETH_USING_ETHASH
 		StructuredLogger::chainNewHead(
 			_block.info.headerHash(WithoutProof).abridged(),
 			_block.info.proof.nonce.abridged(),
 			currentHash().abridged(),
 			_block.info.parentHash.abridged()
 		);
+#endif
 	}
 	else
 	{
diff --git a/libethereum/BlockQueue.cpp b/libethereum/BlockQueue.cpp
index 690fb60ee..b6c548c1f 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.proof.mixHash = work.hash;
+			bi.sha3Uncles = 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.proof.mixHash == work.hash)
+				if (it->verified.info.sha3Uncles == 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.proof.mixHash == work.hash)
+			if (!m_verifying.empty() && m_verifying.front().verified.info.sha3Uncles == 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.proof.mixHash == work.hash)
+					if (i.verified.info.sha3Uncles == 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.proof.mixHash))
+				if (m_knownBad.count(b.verified.info.parentHash) || m_knownBad.count(b.verified.info.sha3Uncles))
 				{
-					h256 const& h = b.blockData.size() != 0 ? b.verified.info.hash() : b.verified.info.proof.mixHash;
+					h256 const& h = b.blockData.size() != 0 ? b.verified.info.hash() : b.verified.info.sha3Uncles;
 					m_knownBad.insert(h);
 					m_readySet.erase(h);
 					collectUnknownBad_WITH_BOTH_LOCKS(h);
diff --git a/libethereum/Client.cpp b/libethereum/Client.cpp
index 054cd1c9b..b3495d912 100644
--- a/libethereum/Client.cpp
+++ b/libethereum/Client.cpp
@@ -325,7 +325,7 @@ void Client::killChain()
 
 	m_tq.clear();
 	m_bq.clear();
-	m_farm.stop();
+	m_farm.disable();
 
 	{
 		WriteGuard l(x_postMine);
@@ -706,19 +706,10 @@ void Client::rejigMining()
 		}
 
 		if (m_wouldMine)
-		{
-			m_farm.setWork(m_miningInfo);
-			if (m_turboMining)
-				m_farm.startGPU();
-			else
-				m_farm.startCPU();
-
-			m_farm.setWork(m_miningInfo);
-			Ethash::ensurePrecomputed(m_bc.number());
-		}
+			m_farm.sealBlock(m_miningInfo);
 	}
 	if (!m_wouldMine)
-		m_farm.stop();
+		m_farm.disable();
 }
 
 void Client::noteChanged(h256Hash const& _filters)
diff --git a/libethereum/Client.h b/libethereum/Client.h
index fac54b010..16672ce45 100644
--- a/libethereum/Client.h
+++ b/libethereum/Client.h
@@ -310,7 +310,7 @@ private:
 
 	std::weak_ptr<EthereumHost> m_host;		///< Our Ethereum Host. Don't do anything if we can't lock.
 
-	GenericFarm<ProofOfWork> m_farm;		///< Our mining farm.
+	ProofOfWork::Farm m_farm;		///< Our mining farm.
 
 	Handler<> m_tqReady;
 	Handler<> m_bqReady;
diff --git a/libethereum/State.cpp b/libethereum/State.cpp
index bf55a50ff..1656109a9 100644
--- a/libethereum/State.cpp
+++ b/libethereum/State.cpp
@@ -976,12 +976,12 @@ void State::completeMine()
 	ret.swapOut(m_currentBytes);
 	m_currentBlock.noteDirty();
 	cnote << "Mined " << m_currentBlock.hash() << "(parent: " << m_currentBlock.parentHash << ")";
-	StructuredLogger::minedNewBlock(
+/*	StructuredLogger::minedNewBlock(
 		m_currentBlock.hash().abridged(),
 		m_currentBlock.proof.nonce.abridged(),
 		"", //TODO: chain head hash here ??
 		m_currentBlock.parentHash.abridged()
-	);
+	);*/
 
 	// Quickly reset the transactions.
 	// TODO: Leave this in a better state than this limbo, or at least record that it's in limbo.
diff --git a/libethereum/State.h b/libethereum/State.h
index 0555b6dcd..f6a8471ea 100644
--- a/libethereum/State.h
+++ b/libethereum/State.h
@@ -173,7 +173,7 @@ public:
 		if (!PoW::verify(m_currentBlock))
 			return false;
 
-		cnote << "Completed" << m_currentBlock.headerHash(WithoutProof) << m_currentBlock.proof.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 f7c09ebc2..7d63ed165 100644
--- a/libweb3jsonrpc/JsonHelper.cpp
+++ b/libweb3jsonrpc/JsonHelper.cpp
@@ -102,9 +102,11 @@ Json::Value toJson(dev::eth::BlockInfo const& _bi)
 		res["logsBloom"] = toJS(_bi.logBloom);
 		res["target"] = toJS(_bi.boundary());
 
+#if ETH_USING_ETHASH
 		// TODO: move into ProofOfWork.
 		res["nonce"] = toJS(_bi.proof.nonce);
 		res["seedHash"] = toJS(_bi.proofCache());
+#endif
 	}
 	return res;
 }
diff --git a/libweb3jsonrpc/WebThreeStubServerBase.cpp b/libweb3jsonrpc/WebThreeStubServerBase.cpp
index 166fbb1bb..f2a95f785 100644
--- a/libweb3jsonrpc/WebThreeStubServerBase.cpp
+++ b/libweb3jsonrpc/WebThreeStubServerBase.cpp
@@ -733,10 +733,12 @@ Json::Value WebThreeStubServerBase::eth_getLogs(Json::Value const& _json)
 Json::Value WebThreeStubServerBase::eth_getWork()
 {
 	Json::Value ret(Json::arrayValue);
+#if ETH_USING_ETHASH
 	auto r = client()->getWork();
 	ret.append(toJS(r.headerHash));
 	ret.append(toJS(r.seedHash));
 	ret.append(toJS(r.boundary));
+#endif
 	return ret;
 }
 
@@ -744,7 +746,13 @@ bool WebThreeStubServerBase::eth_submitWork(string const& _nonce, string const&,
 {
 	try
 	{
-		return client()->submitWork(ProofOfWork::Solution{jsToFixed<Nonce::size>(_nonce), jsToFixed<32>(_mixHash)});
+#if ETH_USING_ETHASH
+		return client()->submitWork(Ethash::Solution{jsToFixed<Nonce::size>(_nonce), jsToFixed<32>(_mixHash)});
+#else
+		(void)_nonce;
+		(void)_mixHash;
+		return false;
+#endif
 	}
 	catch (...)
 	{