class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE TF_SignerBase : public TF_SignatureSchemeBase<PK_Signer, TF_Base<RandomizedTrapdoorFunctionInverse, PK_SignatureMessageEncodingMethod> >
{
public:
	void InputRecoverableMessage(PK_MessageAccumulator &messageAccumulator, const byte *recoverableMessage, unsigned int recoverableMessageLength) const;
	unsigned int SignAndRestart(RandomNumberGenerator &rng, PK_MessageAccumulator &messageAccumulator, byte *signature, bool restart=true) const;
};

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE TF_VerifierBase : public TF_SignatureSchemeBase<PK_Verifier, TF_Base<TrapdoorFunction, PK_SignatureMessageEncodingMethod> >
{
public:
	void InputSignature(PK_MessageAccumulator &messageAccumulator, const byte *signature, unsigned int signatureLength) const;
	bool VerifyAndRestart(PK_MessageAccumulator &messageAccumulator) const;
	DecodingResult RecoverAndRestart(byte *recoveredMessage, PK_MessageAccumulator &recoveryAccumulator) const;
};

// ********************************************************

//! _
template <class T1, class T2, class T3>
struct TF_CryptoSchemeOptions
{
	typedef T1 AlgorithmInfo;
	typedef T2 Keys;
	typedef typename Keys::PrivateKey PrivateKey;
	typedef typename Keys::PublicKey PublicKey;
	typedef T3 MessageEncodingMethod;
};

//! _
template <class T1, class T2, class T3, class T4>
struct TF_SignatureSchemeOptions : public TF_CryptoSchemeOptions<T1, T2, T3>
{
	typedef T4 HashFunction;
};

//! _
template <class KEYS>
class CRYPTOPP_NO_VTABLE PublicKeyCopier
{
public:
	typedef typename KEYS::PublicKey KeyClass;
	virtual void CopyKeyInto(typename KEYS::PublicKey &key) const =0;
};

//! _
template <class KEYS>
class CRYPTOPP_NO_VTABLE PrivateKeyCopier
{
public:
	typedef typename KEYS::PrivateKey KeyClass;
	virtual void CopyKeyInto(typename KEYS::PublicKey &key) const =0;
	virtual void CopyKeyInto(typename KEYS::PrivateKey &key) const =0;
};

//! _
template <class BASE, class SCHEME_OPTIONS, class KEY>
class CRYPTOPP_NO_VTABLE TF_ObjectImplBase : public AlgorithmImpl<BASE, typename SCHEME_OPTIONS::AlgorithmInfo>
{
public:
	typedef SCHEME_OPTIONS SchemeOptions;
	typedef KEY KeyClass;

	PublicKey & AccessPublicKey() {return AccessKey();}
	const PublicKey & GetPublicKey() const {return GetKey();}

	PrivateKey & AccessPrivateKey() {return AccessKey();}
	const PrivateKey & GetPrivateKey() const {return GetKey();}

	virtual const KeyClass & GetKey() const =0;
	virtual KeyClass & AccessKey() =0;

	const KeyClass & GetTrapdoorFunction() const {return GetKey();}

	PK_MessageAccumulator * NewSignatureAccumulator(RandomNumberGenerator &rng) const
	{
		return new PK_MessageAccumulatorImpl<CPP_TYPENAME SCHEME_OPTIONS::HashFunction>;
	}
	PK_MessageAccumulator * NewVerificationAccumulator() const
	{
		return new PK_MessageAccumulatorImpl<CPP_TYPENAME SCHEME_OPTIONS::HashFunction>;
	}

protected:
	const typename BASE::MessageEncodingInterface & GetMessageEncodingInterface() const 
		{return Singleton<CPP_TYPENAME SCHEME_OPTIONS::MessageEncodingMethod>().Ref();}
	const TrapdoorFunctionBounds & GetTrapdoorFunctionBounds() const 
		{return GetKey();}
	const typename BASE::TrapdoorFunctionInterface & GetTrapdoorFunctionInterface() const 
		{return GetKey();}

	// for signature scheme
	HashIdentifier GetHashIdentifier() const
	{
        typedef CPP_TYPENAME SchemeOptions::MessageEncodingMethod::HashIdentifierLookup::template HashIdentifierLookup2<CPP_TYPENAME SchemeOptions::HashFunction> L;
        return L::Lookup();
	}
	unsigned int GetDigestSize() const
	{
		typedef CPP_TYPENAME SchemeOptions::HashFunction H;
		return H::DIGESTSIZE;
	}
};

//! _
template <class BASE, class SCHEME_OPTIONS, class KEY>
class TF_ObjectImplExtRef : public TF_ObjectImplBase<BASE, SCHEME_OPTIONS, KEY>
{
public:
	TF_ObjectImplExtRef(const KEY *pKey = NULL) : m_pKey(pKey) {}
	void SetKeyPtr(const KEY *pKey) {m_pKey = pKey;}

	const KEY & GetKey() const {return *m_pKey;}
	KEY & AccessKey() {throw NotImplemented("TF_ObjectImplExtRef: cannot modify refererenced key");}

private:
	const KEY * m_pKey;
};

//! _
template <class BASE, class SCHEME_OPTIONS, class KEY_COPIER>
class CRYPTOPP_NO_VTABLE TF_ObjectImpl : public TF_ObjectImplBase<TwoBases<BASE, KEY_COPIER>, SCHEME_OPTIONS, typename KEY_COPIER::KeyClass>
{
public:
	typedef typename KEY_COPIER::KeyClass KeyClass;

	const KeyClass & GetKey() const {return m_trapdoorFunction;}
	KeyClass & AccessKey() {return m_trapdoorFunction;}

	void CopyKeyInto(typename SCHEME_OPTIONS::PrivateKey &key) const {key = GetKey();}
	void CopyKeyInto(typename SCHEME_OPTIONS::PublicKey &key) const {key = GetKey();}

private:
	KeyClass m_trapdoorFunction;
};

//! _
template <class SCHEME_OPTIONS>
class TF_DecryptorImpl : public TF_ObjectImpl<TF_DecryptorBase, SCHEME_OPTIONS, PrivateKeyCopier<typename SCHEME_OPTIONS::Keys> >
{
};

//! _
template <class SCHEME_OPTIONS>
class TF_EncryptorImpl : public TF_ObjectImpl<TF_EncryptorBase, SCHEME_OPTIONS, PublicKeyCopier<typename SCHEME_OPTIONS::Keys> >
{
};

//! _
template <class SCHEME_OPTIONS>
class TF_SignerImpl : public TF_ObjectImpl<TF_SignerBase, SCHEME_OPTIONS, PrivateKeyCopier<typename SCHEME_OPTIONS::Keys> >
{
};

//! _
template <class SCHEME_OPTIONS>
class TF_VerifierImpl : public TF_ObjectImpl<TF_VerifierBase, SCHEME_OPTIONS, PublicKeyCopier<typename SCHEME_OPTIONS::Keys> >
{
};

// ********************************************************

//! _
class CRYPTOPP_NO_VTABLE MaskGeneratingFunction
{
public:
	virtual ~MaskGeneratingFunction() {}
	virtual void GenerateAndMask(HashTransformation &hash, byte *output, unsigned int outputLength, const byte *input, unsigned int inputLength, bool mask = true) const =0;
};

CRYPTOPP_DLL void P1363_MGF1KDF2_Common(HashTransformation &hash, byte *output, unsigned int outputLength, const byte *input, unsigned int inputLength, const byte *derivationParams, unsigned int derivationParamsLength, bool mask, unsigned int counterStart);

//! _
class P1363_MGF1 : public MaskGeneratingFunction
{
public:
	static const char * StaticAlgorithmName() {return "MGF1";}
	void GenerateAndMask(HashTransformation &hash, byte *output, unsigned int outputLength, const byte *input, unsigned int inputLength, bool mask = true) const
	{
		P1363_MGF1KDF2_Common(hash, output, outputLength, input, inputLength, NULL, 0, mask, 0);
	}
};

// ********************************************************

//! _
template <class H>
class P1363_KDF2
{
public:
	static void DeriveKey(byte *output, unsigned int outputLength, const byte *input, unsigned int inputLength, const byte *derivationParams, unsigned int derivationParamsLength)
	{
		H h;
		P1363_MGF1KDF2_Common(h, output, outputLength, input, inputLength, derivationParams, derivationParamsLength, false, 1);
	}
};

// ********************************************************

//! to be thrown by DecodeElement and AgreeWithStaticPrivateKey
class DL_BadElement : public InvalidDataFormat
{
public:
	DL_BadElement() : InvalidDataFormat("CryptoPP: invalid group element") {}
};

//! interface for DL group parameters
template <class T>
class CRYPTOPP_NO_VTABLE DL_GroupParameters : public CryptoParameters
{
	typedef DL_GroupParameters<T> ThisClass;
	
public:
	typedef T Element;

	DL_GroupParameters() : m_validationLevel(0) {}

	// CryptoMaterial
	bool Validate(RandomNumberGenerator &rng, unsigned int level) const
	{
		if (!GetBasePrecomputation().IsInitialized())
			return false;

		if (m_validationLevel > level)
			return true;

		bool pass = ValidateGroup(rng, level);
		pass = pass && ValidateElement(level, GetSubgroupGenerator(), &GetBasePrecomputation());

		m_validationLevel = pass ? level+1 : 0;

		return pass;
	}

	bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
	{
		return GetValueHelper(this, name, valueType, pValue)
			CRYPTOPP_GET_FUNCTION_ENTRY(SubgroupOrder)
			CRYPTOPP_GET_FUNCTION_ENTRY(SubgroupGenerator)
			;
	}

	bool SupportsPrecomputation() const {return true;}

	void Precompute(unsigned int precomputationStorage=16)
	{
		AccessBasePrecomputation().Precompute(GetGroupPrecomputation(), GetSubgroupOrder().BitCount(), precomputationStorage);
	}

	void LoadPrecomputation(BufferedTransformation &storedPrecomputation)
	{
		AccessBasePrecomputation().Load(GetGroupPrecomputation(), storedPrecomputation);
		m_validationLevel = 0;
	}

	void SavePrecomputation(BufferedTransformation &storedPrecomputation) const
	{
		GetBasePrecomputation().Save(GetGroupPrecomputation(), storedPrecomputation);
	}

	// non-inherited
	virtual const Element & GetSubgroupGenerator() const {return GetBasePrecomputation().GetBase(GetGroupPrecomputation());}
	virtual void SetSubgroupGenerator(const Element &base) {AccessBasePrecomputation().SetBase(GetGroupPrecomputation(), base);}
	virtual Element ExponentiateBase(const Integer &exponent) const
	{
		return GetBasePrecomputation().Exponentiate(GetGroupPrecomputation(), exponent);
	}
	virtual Element ExponentiateElement(const Element &base, const Integer &exponent) const
	{
		Element result;
		SimultaneousExponentiate(&result, base, &exponent, 1);
		return result;
	}

	virtual const DL_GroupPrecomputation<Element> & GetGroupPrecomputation() const =0;
	virtual const DL_FixedBasePrecomputation<Element> & GetBasePrecomputation() const =0;
	virtual DL_FixedBasePrecomputation<Element> & AccessBasePrecomputation() =0;
	virtual const Integer & GetSubgroupOrder() const =0;	// order of subgroup generated by base element
	virtual Integer GetMaxExponent() const =0;
	virtual Integer GetGroupOrder() const {return GetSubgroupOrder()*GetCofactor();}	// one of these two needs to be overriden
	virtual Integer GetCofactor() const {return GetGroupOrder()/GetSubgroupOrder();}
	virtual unsigned int GetEncodedElementSize(bool reversible) const =0;
	virtual void EncodeElement(bool reversible, const Element &element, byte *encoded) const =0;
	virtual Element DecodeElement(const byte *encoded, bool checkForGroupMembership) const =0;
	virtual Integer ConvertElementToInteger(const Element &element) const =0;
	virtual bool ValidateGroup(RandomNumberGenerator &rng, unsigned int level) const =0;
	virtual bool ValidateElement(unsigned int level, const Element &element, const DL_FixedBasePrecomputation<Element> *precomp) const =0;
	virtual bool FastSubgroupCheckAvailable() const =0;
	virtual bool IsIdentity(const Element &element) const =0;
	virtual void SimultaneousExponentiate(Element *results, const Element &base, const Integer *exponents, unsigned int exponentsCount) const =0;

protected:
	void ParametersChanged() {m_validationLevel = 0;}

private:
	mutable unsigned int m_validationLevel;
};

//! _
template <class GROUP_PRECOMP, class BASE_PRECOMP = DL_FixedBasePrecomputationImpl<CPP_TYPENAME GROUP_PRECOMP::Element>, class BASE = DL_GroupParameters<CPP_TYPENAME GROUP_PRECOMP::Element> >
class DL_GroupParametersImpl : public BASE
{
public:
	typedef GROUP_PRECOMP GroupPrecomputation;
	typedef typename GROUP_PRECOMP::Element Element;
	typedef BASE_PRECOMP BasePrecomputation;
	
	const DL_GroupPrecomputation<Element> & GetGroupPrecomputation() const {return m_groupPrecomputation;}
	const DL_FixedBasePrecomputation<Element> & GetBasePrecomputation() const {return m_gpc;}
	DL_FixedBasePrecomputation<Element> & AccessBasePrecomputation() {return m_gpc;}

protected:
	GROUP_PRECOMP m_groupPrecomputation;
	BASE_PRECOMP m_gpc;
};

//! _
template <class T>
class CRYPTOPP_NO_VTABLE DL_Key
{
public:
	virtual const DL_GroupParameters<T> & GetAbstractGroupParameters() const =0;
	virtual DL_GroupParameters<T> & AccessAbstractGroupParameters() =0;
};

//! interface for DL public keys
template <class T>
class CRYPTOPP_NO_VTABLE DL_PublicKey : public DL_Key<T>
{
	typedef DL_PublicKey<T> ThisClass;

public: