bool AllowNonrecoverablePart() const 
		{return GetMessageEncodingInterface().AllowNonrecoverablePart();}
	bool RecoverablePartFirst() const 
		{return GetMessageEncodingInterface().RecoverablePartFirst();}

protected:
	unsigned int MessageRepresentativeLength() const {return BitsToBytes(MessageRepresentativeBitLength());}
	unsigned int MessageRepresentativeBitLength() const {return this->GetAbstractGroupParameters().GetSubgroupOrder().BitCount();}

	virtual const DL_ElgamalLikeSignatureAlgorithm<CPP_TYPENAME KEY_INTERFACE::Element> & GetSignatureAlgorithm() const =0;
	virtual const PK_SignatureMessageEncodingMethod & GetMessageEncodingInterface() const =0;
	virtual HashIdentifier GetHashIdentifier() const =0;
	virtual unsigned int GetDigestSize() const =0;
};

//! _
template <class T>
class CRYPTOPP_NO_VTABLE DL_SignerBase : public DL_SignatureSchemeBase<PK_Signer, DL_PrivateKey<T> >
{
public:
	// for validation testing
	void RawSign(const Integer &k, const Integer &e, Integer &r, Integer &s) const
	{
		const DL_ElgamalLikeSignatureAlgorithm<T> &alg = this->GetSignatureAlgorithm();
		const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
		const DL_PrivateKey<T> &key = this->GetKeyInterface();

		r = params.ConvertElementToInteger(params.ExponentiateBase(k));
		alg.Sign(params, key.GetPrivateExponent(), k, e, r, s);
	}

	void InputRecoverableMessage(PK_MessageAccumulator &messageAccumulator, const byte *recoverableMessage, unsigned int recoverableMessageLength) const
	{
		PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
		ma.m_recoverableMessage.Assign(recoverableMessage, recoverableMessageLength);
		this->GetMessageEncodingInterface().ProcessRecoverableMessage(ma.AccessHash(), 
			recoverableMessage, recoverableMessageLength, 
			ma.m_presignature, ma.m_presignature.size(),
			ma.m_semisignature);
	}

	unsigned int SignAndRestart(RandomNumberGenerator &rng, PK_MessageAccumulator &messageAccumulator, byte *signature, bool restart) const
	{
		this->GetMaterial().DoQuickSanityCheck();

		PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
		const DL_ElgamalLikeSignatureAlgorithm<T> &alg = this->GetSignatureAlgorithm();
		const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
		const DL_PrivateKey<T> &key = this->GetKeyInterface();

		SecByteBlock representative(this->MessageRepresentativeLength());
		this->GetMessageEncodingInterface().ComputeMessageRepresentative(
			rng, 
			ma.m_recoverableMessage, ma.m_recoverableMessage.size(), 
			ma.AccessHash(), this->GetHashIdentifier(), ma.m_empty, 
			representative, this->MessageRepresentativeBitLength());
		ma.m_empty = true;
		Integer e(representative, representative.size());

		Integer r;
		if (this->MaxRecoverableLength() > 0)
			r.Decode(ma.m_semisignature, ma.m_semisignature.size());
		else
			r.Decode(ma.m_presignature, ma.m_presignature.size());
		Integer s;
		alg.Sign(params, key.GetPrivateExponent(), ma.m_k, e, r, s);

		unsigned int rLen = alg.RLen(params);
		r.Encode(signature, rLen);
		s.Encode(signature+rLen, alg.SLen(params));

		if (restart)
			RestartMessageAccumulator(rng, ma);

		return this->SignatureLength();
	}

protected:
	void RestartMessageAccumulator(RandomNumberGenerator &rng, PK_MessageAccumulatorBase &ma) const
	{
		const DL_ElgamalLikeSignatureAlgorithm<T> &alg = this->GetSignatureAlgorithm();
		const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
		ma.m_k.Randomize(rng, 1, params.GetSubgroupOrder()-1);
		ma.m_presignature.New(params.GetEncodedElementSize(false));
		params.ConvertElementToInteger(params.ExponentiateBase(ma.m_k)).Encode(ma.m_presignature, ma.m_presignature.size());
	}
};

//! _
template <class T>
class CRYPTOPP_NO_VTABLE DL_VerifierBase : public DL_SignatureSchemeBase<PK_Verifier, DL_PublicKey<T> >
{
public:
	void InputSignature(PK_MessageAccumulator &messageAccumulator, const byte *signature, unsigned int signatureLength) const
	{
		PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
		const DL_ElgamalLikeSignatureAlgorithm<T> &alg = this->GetSignatureAlgorithm();
		const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();

		unsigned int rLen = alg.RLen(params);
		ma.m_semisignature.Assign(signature, rLen);
		ma.m_s.Decode(signature+rLen, alg.SLen(params));

		this->GetMessageEncodingInterface().ProcessSemisignature(ma.AccessHash(), ma.m_semisignature, ma.m_semisignature.size());
	}
	
	bool VerifyAndRestart(PK_MessageAccumulator &messageAccumulator) const
	{
		this->GetMaterial().DoQuickSanityCheck();

		PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
		const DL_ElgamalLikeSignatureAlgorithm<T> &alg = this->GetSignatureAlgorithm();
		const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
		const DL_PublicKey<T> &key = this->GetKeyInterface();

		SecByteBlock representative(this->MessageRepresentativeLength());
		this->GetMessageEncodingInterface().ComputeMessageRepresentative(NullRNG(), ma.m_recoverableMessage, ma.m_recoverableMessage.size(), 
			ma.AccessHash(), this->GetHashIdentifier(), ma.m_empty,
			representative, this->MessageRepresentativeBitLength());
		ma.m_empty = true;
		Integer e(representative, representative.size());

		Integer r(ma.m_semisignature, ma.m_semisignature.size());
		return alg.Verify(params, key, e, r, ma.m_s);
	}

	DecodingResult RecoverAndRestart(byte *recoveredMessage, PK_MessageAccumulator &messageAccumulator) const
	{
		this->GetMaterial().DoQuickSanityCheck();

		PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
		const DL_ElgamalLikeSignatureAlgorithm<T> &alg = this->GetSignatureAlgorithm();
		const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
		const DL_PublicKey<T> &key = this->GetKeyInterface();

		SecByteBlock representative(this->MessageRepresentativeLength());
		this->GetMessageEncodingInterface().ComputeMessageRepresentative(
			NullRNG(), 
			ma.m_recoverableMessage, ma.m_recoverableMessage.size(), 
			ma.AccessHash(), this->GetHashIdentifier(), ma.m_empty,
			representative, this->MessageRepresentativeBitLength());
		ma.m_empty = true;
		Integer e(representative, representative.size());

		ma.m_presignature.New(params.GetEncodedElementSize(false));
		Integer r(ma.m_semisignature, ma.m_semisignature.size());
		alg.RecoverPresignature(params, key, r, ma.m_s).Encode(ma.m_presignature, ma.m_presignature.size());

		return this->GetMessageEncodingInterface().RecoverMessageFromSemisignature(
			ma.AccessHash(), this->GetHashIdentifier(),
			ma.m_presignature, ma.m_presignature.size(),
			ma.m_semisignature, ma.m_semisignature.size(),
			recoveredMessage);
	}
};

//! _
template <class PK, class KI>
class CRYPTOPP_NO_VTABLE DL_CryptoSystemBase : public PK, public DL_Base<KI>
{
public:
	typedef typename DL_Base<KI>::Element Element;

	unsigned int MaxPlaintextLength(unsigned int ciphertextLength) const
	{
		unsigned int minLen = this->GetAbstractGroupParameters().GetEncodedElementSize(true);
		return ciphertextLength < minLen ? 0 : GetSymmetricEncryptionAlgorithm().GetMaxSymmetricPlaintextLength(ciphertextLength - minLen);
	}

	unsigned int CiphertextLength(unsigned int plaintextLength) const
	{
		unsigned int len = GetSymmetricEncryptionAlgorithm().GetSymmetricCiphertextLength(plaintextLength);
		return len == 0 ? 0 : this->GetAbstractGroupParameters().GetEncodedElementSize(true) + len;
	}

	bool ParameterSupported(const char *name) const
		{return GetKeyDerivationAlgorithm().ParameterSupported(name) || GetSymmetricEncryptionAlgorithm().ParameterSupported(name);}

protected:
	virtual const DL_KeyAgreementAlgorithm<Element> & GetKeyAgreementAlgorithm() const =0;
	virtual const DL_KeyDerivationAlgorithm<Element> & GetKeyDerivationAlgorithm() const =0;
	virtual const DL_SymmetricEncryptionAlgorithm & GetSymmetricEncryptionAlgorithm() const =0;
};

//! _
template <class T>
class CRYPTOPP_NO_VTABLE DL_DecryptorBase : public DL_CryptoSystemBase<PK_Decryptor, DL_PrivateKey<T> >
{
public:
	typedef T Element;

	DecodingResult Decrypt(RandomNumberGenerator &rng, const byte *ciphertext, unsigned int ciphertextLength, byte *plaintext, const NameValuePairs &parameters = g_nullNameValuePairs) const
	{
		try
		{
			const DL_KeyAgreementAlgorithm<T> &agreeAlg = this->GetKeyAgreementAlgorithm();
			const DL_KeyDerivationAlgorithm<T> &derivAlg = this->GetKeyDerivationAlgorithm();
			const DL_SymmetricEncryptionAlgorithm &encAlg = this->GetSymmetricEncryptionAlgorithm();
			const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
			const DL_PrivateKey<T> &key = this->GetKeyInterface();

			Element q = params.DecodeElement(ciphertext, true);
			unsigned int elementSize = params.GetEncodedElementSize(true);
			ciphertext += elementSize;
			ciphertextLength -= elementSize;

			Element z = agreeAlg.AgreeWithStaticPrivateKey(params, q, true, key.GetPrivateExponent());

			SecByteBlock derivedKey(encAlg.GetSymmetricKeyLength(encAlg.GetMaxSymmetricPlaintextLength(ciphertextLength)));
			derivAlg.Derive(params, derivedKey, derivedKey.size(), z, q, parameters);

			return encAlg.SymmetricDecrypt(derivedKey, ciphertext, ciphertextLength, plaintext, parameters);
		}
		catch (DL_BadElement &)
		{
			return DecodingResult();
		}
	}
};

//! _
template <class T>
class CRYPTOPP_NO_VTABLE DL_EncryptorBase : public DL_CryptoSystemBase<PK_Encryptor, DL_PublicKey<T> >
{
public:
	typedef T Element;

	void Encrypt(RandomNumberGenerator &rng, const byte *plaintext, unsigned int plaintextLength, byte *ciphertext, const NameValuePairs &parameters = g_nullNameValuePairs) const
	{
		const DL_KeyAgreementAlgorithm<T> &agreeAlg = this->GetKeyAgreementAlgorithm();
		const DL_KeyDerivationAlgorithm<T> &derivAlg = this->GetKeyDerivationAlgorithm();
		const DL_SymmetricEncryptionAlgorithm &encAlg = this->GetSymmetricEncryptionAlgorithm();
		const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
		const DL_PublicKey<T> &key = this->GetKeyInterface();

		Integer x(rng, Integer::One(), params.GetMaxExponent());
		Element q = params.ExponentiateBase(x);
		params.EncodeElement(true, q, ciphertext);
		unsigned int elementSize = params.GetEncodedElementSize(true);
		ciphertext += elementSize;

		Element z = agreeAlg.AgreeWithEphemeralPrivateKey(params, key.GetPublicPrecomputation(), x);

		SecByteBlock derivedKey(encAlg.GetSymmetricKeyLength(plaintextLength));
		derivAlg.Derive(params, derivedKey, derivedKey.size(), z, q, parameters);

		encAlg.SymmetricEncrypt(rng, derivedKey, plaintext, plaintextLength, ciphertext, parameters);
	}
};

//! _
template <class T1, class T2>
struct DL_SchemeOptionsBase
{
	typedef T1 AlgorithmInfo;
	typedef T2 GroupParameters;
	typedef typename GroupParameters::Element Element;
};

//! _
template <class T1, class T2>
struct DL_KeyedSchemeOptions : public DL_SchemeOptionsBase<T1, typename T2::PublicKey::GroupParameters>
{
	typedef T2 Keys;
	typedef typename Keys::PrivateKey PrivateKey;
	typedef typename Keys::PublicKey PublicKey;
};

//! _
template <class T1, class T2, class T3, class T4, class T5>
struct DL_SignatureSchemeOptions : public DL_KeyedSchemeOptions<T1, T2>
{
	typedef T3 SignatureAlgorithm;
	typedef T4 MessageEncodingMethod;
	typedef T5 HashFunction;
};

//! _
template <class T1, class T2, class T3, class T4, class T5>
struct DL_CryptoSchemeOptions : public DL_KeyedSchemeOptions<T1, T2>
{
	typedef T3 KeyAgreementAlgorithm;
	typedef T4 KeyDerivationAlgorithm;
	typedef T5 SymmetricEncryptionAlgorithm;
};

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

	PrivateKey & AccessPrivateKey() {return m_key;}
	PublicKey & AccessPublicKey() {return m_key;}

	// KeyAccessor
	const KEY & GetKey() const {return m_key;}
	KEY & AccessKey() {return m_key;}

protected:
	typename BASE::KeyInterface & AccessKeyInterface() {return m_key;}
	const typename BASE::KeyInterface & GetKeyInterface() const {return m_key;}

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

private:
	KEY m_key;
};

//! _
template <class BASE, class SCHEME_OPTIONS, class KEY>
class CRYPTOPP_NO_VTABLE DL_ObjectImpl : public DL_ObjectImplBase<BASE, SCHEME_OPTIONS, KEY>
{
public:
	typedef typename KEY::Element Element;

protected:
	const DL_ElgamalLikeSignatureAlgorithm<Element> & GetSignatureAlgorithm() const
		{return Singleton<CPP_TYPENAME SCHEME_OPTIONS::SignatureAlgorithm>().Ref();}
	const DL_KeyAgreementAlgorithm<Element> & GetKeyAgreementAlgorithm() const