pubkey.h

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// pubkey.h - written and placed in the public domain by Wei Dai

#ifndef CRYPTOPP_PUBKEY_H
#define CRYPTOPP_PUBKEY_H

/** \file

        This file contains helper classes/functions for implementing public key algorithms.

        The class hierachies in this .h file tend to look like this:
<pre>
                  x1
                 / \
                y1  z1
                 |  |
            x2<y1>  x2<z1>
                 |  |
                y2  z2
                 |  |
            x3<y2>  x3<z2>
                 |  |
                y3  z3
</pre>
        - x1, y1, z1 are abstract interface classes defined in cryptlib.h
        - x2, y2, z2 are implementations of the interfaces using "abstract policies", which
          are pure virtual functions that should return interfaces to interchangeable algorithms.
          These classes have "Base" suffixes.
        - x3, y3, z3 hold actual algorithms and implement those virtual functions.
          These classes have "Impl" suffixes.

        The "TF_" prefix means an implementation using trapdoor functions on integers.
        The "DL_" prefix means an implementation using group operations (in groups where discrete log is hard).
*/

#include "modarith.h"
#include "filters.h"
#include "eprecomp.h"
#include "fips140.h"
#include "argnames.h"
#include <memory>

// VC60 workaround: this macro is defined in shlobj.h and conflicts with a template parameter used in this file
#undef INTERFACE

NAMESPACE_BEGIN(CryptoPP)

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE TrapdoorFunctionBounds
{
public:
        virtual ~TrapdoorFunctionBounds() {}

        virtual Integer PreimageBound() const =0;
        virtual Integer ImageBound() const =0;
        virtual Integer MaxPreimage() const {return --PreimageBound();}
        virtual Integer MaxImage() const {return --ImageBound();}
};

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE RandomizedTrapdoorFunction : public TrapdoorFunctionBounds
{
public:
        virtual Integer ApplyRandomizedFunction(RandomNumberGenerator &rng, const Integer &x) const =0;
        virtual bool IsRandomized() const {return true;}
};

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE TrapdoorFunction : public RandomizedTrapdoorFunction
{
public:
        Integer ApplyRandomizedFunction(RandomNumberGenerator &rng, const Integer &x) const
                {return ApplyFunction(x);}
        bool IsRandomized() const {return false;}

        virtual Integer ApplyFunction(const Integer &x) const =0;
};

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE RandomizedTrapdoorFunctionInverse
{
public:
        virtual ~RandomizedTrapdoorFunctionInverse() {}

        virtual Integer CalculateRandomizedInverse(RandomNumberGenerator &rng, const Integer &x) const =0;
        virtual bool IsRandomized() const {return true;}
};

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE TrapdoorFunctionInverse : public RandomizedTrapdoorFunctionInverse
{
public:
        virtual ~TrapdoorFunctionInverse() {}

        Integer CalculateRandomizedInverse(RandomNumberGenerator &rng, const Integer &x) const
                {return CalculateInverse(rng, x);}
        bool IsRandomized() const {return false;}

        virtual Integer CalculateInverse(RandomNumberGenerator &rng, const Integer &x) const =0;
};

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

//! message encoding method for public key encryption
class CRYPTOPP_NO_VTABLE PK_EncryptionMessageEncodingMethod
{
public:
        virtual ~PK_EncryptionMessageEncodingMethod() {}

        virtual bool ParameterSupported(const char *name) const {return false;}

        //! max size of unpadded message in bytes, given max size of padded message in bits (1 less than size of modulus)
        virtual size_t MaxUnpaddedLength(size_t paddedLength) const =0;

        virtual void Pad(RandomNumberGenerator &rng, const byte *raw, size_t inputLength, byte *padded, size_t paddedBitLength, const NameValuePairs &parameters) const =0;

        virtual DecodingResult Unpad(const byte *padded, size_t paddedBitLength, byte *raw, const NameValuePairs &parameters) const =0;
};

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

//! _
template <class TFI, class MEI>
class CRYPTOPP_NO_VTABLE TF_Base
{
protected:
        virtual const TrapdoorFunctionBounds & GetTrapdoorFunctionBounds() const =0;

        typedef TFI TrapdoorFunctionInterface;
        virtual const TrapdoorFunctionInterface & GetTrapdoorFunctionInterface() const =0;

        typedef MEI MessageEncodingInterface;
        virtual const MessageEncodingInterface & GetMessageEncodingInterface() const =0;
};

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

//! _
template <class BASE>
class CRYPTOPP_NO_VTABLE PK_FixedLengthCryptoSystemImpl : public BASE
{
public:
        size_t MaxPlaintextLength(size_t ciphertextLength) const
                {return ciphertextLength == FixedCiphertextLength() ? FixedMaxPlaintextLength() : 0;}
        size_t CiphertextLength(size_t plaintextLength) const
                {return plaintextLength <= FixedMaxPlaintextLength() ? FixedCiphertextLength() : 0;}

        virtual size_t FixedMaxPlaintextLength() const =0;
        virtual size_t FixedCiphertextLength() const =0;
};

//! _
template <class INTERFACE, class BASE>
class CRYPTOPP_NO_VTABLE TF_CryptoSystemBase : public PK_FixedLengthCryptoSystemImpl<INTERFACE>, protected BASE
{
public:
        bool ParameterSupported(const char *name) const {return this->GetMessageEncodingInterface().ParameterSupported(name);}
        size_t FixedMaxPlaintextLength() const {return this->GetMessageEncodingInterface().MaxUnpaddedLength(PaddedBlockBitLength());}
        size_t FixedCiphertextLength() const {return this->GetTrapdoorFunctionBounds().MaxImage().ByteCount();}

protected:
        size_t PaddedBlockByteLength() const {return BitsToBytes(PaddedBlockBitLength());}
        size_t PaddedBlockBitLength() const {return this->GetTrapdoorFunctionBounds().PreimageBound().BitCount()-1;}
};

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE TF_DecryptorBase : public TF_CryptoSystemBase<PK_Decryptor, TF_Base<TrapdoorFunctionInverse, PK_EncryptionMessageEncodingMethod> >
{
public:
        DecodingResult Decrypt(RandomNumberGenerator &rng, const byte *ciphertext, size_t ciphertextLength, byte *plaintext, const NameValuePairs &parameters = g_nullNameValuePairs) const;
};

//! _
class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE TF_EncryptorBase : public TF_CryptoSystemBase<PK_Encryptor, TF_Base<RandomizedTrapdoorFunction, PK_EncryptionMessageEncodingMethod> >
{
public:
        void Encrypt(RandomNumberGenerator &rng, const byte *plaintext, size_t plaintextLength, byte *ciphertext, const NameValuePairs &parameters = g_nullNameValuePairs) const;
};

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

typedef std::pair<const byte *, size_t> HashIdentifier;

//! interface for message encoding method for public key signature schemes
class CRYPTOPP_NO_VTABLE PK_SignatureMessageEncodingMethod
{
public:
        virtual ~PK_SignatureMessageEncodingMethod() {}

        virtual size_t MinRepresentativeBitLength(size_t hashIdentifierLength, size_t digestLength) const
                {return 0;}
        virtual size_t MaxRecoverableLength(size_t representativeBitLength, size_t hashIdentifierLength, size_t digestLength) const
                {return 0;}

        bool IsProbabilistic() const 
                {return true;}
        bool AllowNonrecoverablePart() const
                {throw NotImplemented("PK_MessageEncodingMethod: this signature scheme does not support message recovery");}
        virtual bool RecoverablePartFirst() const
                {throw NotImplemented("PK_MessageEncodingMethod: this signature scheme does not support message recovery");}

        // for verification, DL
        virtual void ProcessSemisignature(HashTransformation &hash, const byte *semisignature, size_t semisignatureLength) const {}

        // for signature
        virtual void ProcessRecoverableMessage(HashTransformation &hash, 
                const byte *recoverableMessage, size_t recoverableMessageLength, 
                const byte *presignature, size_t presignatureLength,
                SecByteBlock &semisignature) const
        {
                if (RecoverablePartFirst())
                        assert(!"ProcessRecoverableMessage() not implemented");
        }

        virtual void ComputeMessageRepresentative(RandomNumberGenerator &rng, 
                const byte *recoverableMessage, size_t recoverableMessageLength,
                HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
                byte *representative, size_t representativeBitLength) const =0;

        virtual bool VerifyMessageRepresentative(
                HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
                byte *representative, size_t representativeBitLength) const =0;

        virtual DecodingResult RecoverMessageFromRepresentative(        // for TF
                HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
                byte *representative, size_t representativeBitLength,
                byte *recoveredMessage) const
                {throw NotImplemented("PK_MessageEncodingMethod: this signature scheme does not support message recovery");}

        virtual DecodingResult RecoverMessageFromSemisignature(         // for DL
                HashTransformation &hash, HashIdentifier hashIdentifier,
                const byte *presignature, size_t presignatureLength,
                const byte *semisignature, size_t semisignatureLength,
                byte *recoveredMessage) const
                {throw NotImplemented("PK_MessageEncodingMethod: this signature scheme does not support message recovery");}

        // VC60 workaround
        struct HashIdentifierLookup
        {
                template <class H> struct HashIdentifierLookup2
                {
                        static HashIdentifier CRYPTOPP_API Lookup()
                        {
                                return HashIdentifier(NULL, 0);
                        }
                };
        };
};

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_DeterministicSignatureMessageEncodingMethod : public PK_SignatureMessageEncodingMethod
{
public:
        bool VerifyMessageRepresentative(
                HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
                byte *representative, size_t representativeBitLength) const;
};

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_RecoverableSignatureMessageEncodingMethod : public PK_SignatureMessageEncodingMethod
{
public:
        bool VerifyMessageRepresentative(
                HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
                byte *representative, size_t representativeBitLength) const;
};

class CRYPTOPP_DLL DL_SignatureMessageEncodingMethod_DSA : public PK_DeterministicSignatureMessageEncodingMethod
{
public:
        void ComputeMessageRepresentative(RandomNumberGenerator &rng, 
                const byte *recoverableMessage, size_t recoverableMessageLength,
                HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
                byte *representative, size_t representativeBitLength) const;
};

class CRYPTOPP_DLL DL_SignatureMessageEncodingMethod_NR : public PK_DeterministicSignatureMessageEncodingMethod
{
public:
        void ComputeMessageRepresentative(RandomNumberGenerator &rng, 
                const byte *recoverableMessage, size_t recoverableMessageLength,
                HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
                byte *representative, size_t representativeBitLength) const;
};

class CRYPTOPP_DLL CRYPTOPP_NO_VTABLE PK_MessageAccumulatorBase : public PK_MessageAccumulator
{
public:
        PK_MessageAccumulatorBase() : m_empty(true) {}

        virtual HashTransformation & AccessHash() =0;

        void Update(const byte *input, size_t length)
        {
                AccessHash().Update(input, length);
                m_empty = m_empty && length == 0;
        }

        SecByteBlock m_recoverableMessage, m_representative, m_presignature, m_semisignature;
        Integer m_k, m_s;
        bool m_empty;
};

template <class HASH_ALGORITHM>
class PK_MessageAccumulatorImpl : public PK_MessageAccumulatorBase, protected ObjectHolder<HASH_ALGORITHM>
{
public:
        HashTransformation & AccessHash() {return this->m_object;}
};

//! _
template <class INTERFACE, class BASE>
class CRYPTOPP_NO_VTABLE TF_SignatureSchemeBase : public INTERFACE, protected BASE
{
public:
        size_t SignatureLength() const 
                {return this->GetTrapdoorFunctionBounds().MaxPreimage().ByteCount();}
        size_t MaxRecoverableLength() const 
                {return this->GetMessageEncodingInterface().MaxRecoverableLength(MessageRepresentativeBitLength(), GetHashIdentifier().second, GetDigestSize());}
        size_t MaxRecoverableLengthFromSignatureLength(size_t signatureLength) const
                {return this->MaxRecoverableLength();}

        bool IsProbabilistic() const 
                {return this->GetTrapdoorFunctionInterface().IsRandomized() || this->GetMessageEncodingInterface().IsProbabilistic();}
        bool AllowNonrecoverablePart() const 
                {return this->GetMessageEncodingInterface().AllowNonrecoverablePart();}
        bool RecoverablePartFirst() const 
                {return this->GetMessageEncodingInterface().RecoverablePartFirst();}

protected:
        size_t MessageRepresentativeLength() const {return BitsToBytes(MessageRepresentativeBitLength());}
        size_t MessageRepresentativeBitLength() const {return this->GetTrapdoorFunctionBounds().ImageBound().BitCount()-1;}
        virtual HashIdentifier GetHashIdentifier() const =0;
        virtual size_t GetDigestSize() const =0;
};

//! _
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, size_t recoverableMessageLength) const;
        size_t 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, size_t 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 BASE, class SCHEME_OPTIONS, class KEY_CLASS>
class CRYPTOPP_NO_VTABLE TF_ObjectImplBase : public AlgorithmImpl<BASE, typename SCHEME_OPTIONS::AlgorithmInfo>
{
public:
        typedef SCHEME_OPTIONS SchemeOptions;
        typedef KEY_CLASS 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();
        }
        size_t 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_CLASS>
class CRYPTOPP_NO_VTABLE TF_ObjectImpl : public TF_ObjectImplBase<BASE, SCHEME_OPTIONS, KEY_CLASS>
{
public:
        typedef KEY_CLASS KeyClass;

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

private:
        KeyClass m_trapdoorFunction;
};

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

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

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

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

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

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

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

//! _
class P1363_MGF1 : public MaskGeneratingFunction
{
public:
        static const char * CRYPTOPP_API StaticAlgorithmName() {return "MGF1";}
        void GenerateAndMask(HashTransformation &hash, byte *output, size_t outputLength, const byte *input, size_t 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 CRYPTOPP_API DeriveKey(byte *output, size_t outputLength, const byte *input, size_t inputLength, const byte *derivationParams, size_t 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:
        typedef T Element;

        bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
        {
                return GetValueHelper(this, name, valueType, pValue, &this->GetAbstractGroupParameters())
                                CRYPTOPP_GET_FUNCTION_ENTRY(PublicElement);
        }

        void AssignFrom(const NameValuePairs &source);
        
        // non-inherited
        virtual const Element & GetPublicElement() const {return GetPublicPrecomputation().GetBase(this->GetAbstractGroupParameters().GetGroupPrecomputation());}
        virtual void SetPublicElement(const Element &y) {AccessPublicPrecomputation().SetBase(this->GetAbstractGroupParameters().GetGroupPrecomputation(), y);}
        virtual Element ExponentiatePublicElement(const Integer &exponent) const
        {
                const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
                return GetPublicPrecomputation().Exponentiate(params.GetGroupPrecomputation(), exponent);
        }
        virtual Element CascadeExponentiateBaseAndPublicElement(const Integer &baseExp, const Integer &publicExp) const
        {
                const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();
                return params.GetBasePrecomputation().CascadeExponentiate(params.GetGroupPrecomputation(), baseExp, GetPublicPrecomputation(), publicExp);
        }

        virtual const DL_FixedBasePrecomputation<T> & GetPublicPrecomputation() const =0;
        virtual DL_FixedBasePrecomputation<T> & AccessPublicPrecomputation() =0;
};

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

public:
        typedef T Element;

        void MakePublicKey(DL_PublicKey<T> &pub) const
        {
                pub.AccessAbstractGroupParameters().AssignFrom(this->GetAbstractGroupParameters());
                pub.SetPublicElement(this->GetAbstractGroupParameters().ExponentiateBase(GetPrivateExponent()));
        }

        bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
        {
                return GetValueHelper(this, name, valueType, pValue, &this->GetAbstractGroupParameters())
                                CRYPTOPP_GET_FUNCTION_ENTRY(PrivateExponent);
        }

        void AssignFrom(const NameValuePairs &source)
        {
                this->AccessAbstractGroupParameters().AssignFrom(source);
                AssignFromHelper(this, source)
                        CRYPTOPP_SET_FUNCTION_ENTRY(PrivateExponent);
        }

        virtual const Integer & GetPrivateExponent() const =0;
        virtual void SetPrivateExponent(const Integer &x) =0;
};

template <class T>
void DL_PublicKey<T>::AssignFrom(const NameValuePairs &source)
{
        DL_PrivateKey<T> *pPrivateKey = NULL;
        if (source.GetThisPointer(pPrivateKey))
                pPrivateKey->MakePublicKey(*this);
        else
        {
                this->AccessAbstractGroupParameters().AssignFrom(source);
                AssignFromHelper(this, source)
                        CRYPTOPP_SET_FUNCTION_ENTRY(PublicElement);
        }
}

class OID;

//! _
template <class PK, class GP, class O = OID>
class DL_KeyImpl : public PK
{
public:
        typedef GP GroupParameters;

        O GetAlgorithmID() const {return GetGroupParameters().GetAlgorithmID();}
//      void BERDecode(BufferedTransformation &bt)
//              {PK::BERDecode(bt);}
//      void DEREncode(BufferedTransformation &bt) const
//              {PK::DEREncode(bt);}
        bool BERDecodeAlgorithmParameters(BufferedTransformation &bt)
                {AccessGroupParameters().BERDecode(bt); return true;}
        bool DEREncodeAlgorithmParameters(BufferedTransformation &bt) const
                {GetGroupParameters().DEREncode(bt); return true;}

        const GP & GetGroupParameters() const {return m_groupParameters;}
        GP & AccessGroupParameters() {return m_groupParameters;}

private:
        GP m_groupParameters;
};

class X509PublicKey;
class PKCS8PrivateKey;

//! _
template <class GP>
class DL_PrivateKeyImpl : public DL_PrivateKey<CPP_TYPENAME GP::Element>, public DL_KeyImpl<PKCS8PrivateKey, GP>
{
public:
        typedef typename GP::Element Element;

        // GeneratableCryptoMaterial
        bool Validate(RandomNumberGenerator &rng, unsigned int level) const
        {
                bool pass = GetAbstractGroupParameters().Validate(rng, level);

                const Integer &q = GetAbstractGroupParameters().GetSubgroupOrder();
                const Integer &x = GetPrivateExponent();

                pass = pass && x.IsPositive() && x < q;
                if (level >= 1)
                        pass = pass && Integer::Gcd(x, q) == Integer::One();
                return pass;
        }

        bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
        {
                return GetValueHelper<DL_PrivateKey<Element> >(this, name, valueType, pValue).Assignable();
        }

        void AssignFrom(const NameValuePairs &source)
        {
                AssignFromHelper<DL_PrivateKey<Element> >(this, source);
        }

        void GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &params)
        {
                if (!params.GetThisObject(this->AccessGroupParameters()))
                        this->AccessGroupParameters().GenerateRandom(rng, params);
//              std::pair<const byte *, int> seed;
                Integer x(rng, Integer::One(), GetAbstractGroupParameters().GetMaxExponent());
//                      Integer::ANY, Integer::Zero(), Integer::One(),
//                      params.GetValue("DeterministicKeyGenerationSeed", seed) ? &seed : NULL);
                SetPrivateExponent(x);
        }

        bool SupportsPrecomputation() const {return true;}

        void Precompute(unsigned int precomputationStorage=16)
                {AccessAbstractGroupParameters().Precompute(precomputationStorage);}

        void LoadPrecomputation(BufferedTransformation &storedPrecomputation)
                {AccessAbstractGroupParameters().LoadPrecomputation(storedPrecomputation);}

        void SavePrecomputation(BufferedTransformation &storedPrecomputation) const
                {GetAbstractGroupParameters().SavePrecomputation(storedPrecomputation);}

        // DL_Key
        const DL_GroupParameters<Element> & GetAbstractGroupParameters() const {return this->GetGroupParameters();}
        DL_GroupParameters<Element> & AccessAbstractGroupParameters() {return this->AccessGroupParameters();}

        // DL_PrivateKey
        const Integer & GetPrivateExponent() const {return m_x;}
        void SetPrivateExponent(const Integer &x) {m_x = x;}

        // PKCS8PrivateKey
        void BERDecodePrivateKey(BufferedTransformation &bt, bool, size_t)
                {m_x.BERDecode(bt);}
        void DEREncodePrivateKey(BufferedTransformation &bt) const
                {m_x.DEREncode(bt);}

private:
        Integer m_x;
};

//! _
template <class BASE, class SIGNATURE_SCHEME>
class DL_PrivateKey_WithSignaturePairwiseConsistencyTest : public BASE
{
public:
        void GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &params)
        {
                BASE::GenerateRandom(rng, params);

                if (FIPS_140_2_ComplianceEnabled())
                {
                        typename SIGNATURE_SCHEME::Signer signer(*this);
                        typename SIGNATURE_SCHEME::Verifier verifier(signer);
                        SignaturePairwiseConsistencyTest_FIPS_140_Only(signer, verifier);
                }
        }
};

//! _
template <class GP>
class DL_PublicKeyImpl : public DL_PublicKey<typename GP::Element>, public DL_KeyImpl<X509PublicKey, GP>
{
public:
        typedef typename GP::Element Element;

        // CryptoMaterial
        bool Validate(RandomNumberGenerator &rng, unsigned int level) const
        {
                bool pass = GetAbstractGroupParameters().Validate(rng, level);
                pass = pass && GetAbstractGroupParameters().ValidateElement(level, this->GetPublicElement(), &GetPublicPrecomputation());
                return pass;
        }

        bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const
        {
                return GetValueHelper<DL_PublicKey<Element> >(this, name, valueType, pValue).Assignable();
        }

        void AssignFrom(const NameValuePairs &source)
        {
                AssignFromHelper<DL_PublicKey<Element> >(this, source);
        }

        bool SupportsPrecomputation() const {return true;}

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

        void LoadPrecomputation(BufferedTransformation &storedPrecomputation)
        {
                AccessAbstractGroupParameters().LoadPrecomputation(storedPrecomputation);
                AccessPublicPrecomputation().Load(GetAbstractGroupParameters().GetGroupPrecomputation(), storedPrecomputation);
        }

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

        // DL_Key
        const DL_GroupParameters<Element> & GetAbstractGroupParameters() const {return this->GetGroupParameters();}
        DL_GroupParameters<Element> & AccessAbstractGroupParameters() {return this->AccessGroupParameters();}

        // DL_PublicKey
        const DL_FixedBasePrecomputation<Element> & GetPublicPrecomputation() const {return m_ypc;}
        DL_FixedBasePrecomputation<Element> & AccessPublicPrecomputation() {return m_ypc;}

        // non-inherited
        bool operator==(const DL_PublicKeyImpl<GP> &rhs) const
                {return this->GetGroupParameters() == rhs.GetGroupParameters() && this->GetPublicElement() == rhs.GetPublicElement();}

private:
        typename GP::BasePrecomputation m_ypc;
};

//! interface for Elgamal-like signature algorithms
template <class T>
class CRYPTOPP_NO_VTABLE DL_ElgamalLikeSignatureAlgorithm
{
public:
        virtual void Sign(const DL_GroupParameters<T> &params, const Integer &privateKey, const Integer &k, const Integer &e, Integer &r, Integer &s) const =0;
        virtual bool Verify(const DL_GroupParameters<T> &params, const DL_PublicKey<T> &publicKey, const Integer &e, const Integer &r, const Integer &s) const =0;
        virtual Integer RecoverPresignature(const DL_GroupParameters<T> &params, const DL_PublicKey<T> &publicKey, const Integer &r, const Integer &s) const
                {throw NotImplemented("DL_ElgamalLikeSignatureAlgorithm: this signature scheme does not support message recovery");}
        virtual size_t RLen(const DL_GroupParameters<T> &params) const
                {return params.GetSubgroupOrder().ByteCount();}
        virtual size_t SLen(const DL_GroupParameters<T> &params) const
                {return params.GetSubgroupOrder().ByteCount();}
};

//! interface for DL key agreement algorithms
template <class T>
class CRYPTOPP_NO_VTABLE DL_KeyAgreementAlgorithm
{
public:
        typedef T Element;

        virtual Element AgreeWithEphemeralPrivateKey(const DL_GroupParameters<Element> &params, const DL_FixedBasePrecomputation<Element> &publicPrecomputation, const Integer &privateExponent) const =0;
        virtual Element AgreeWithStaticPrivateKey(const DL_GroupParameters<Element> &params, const Element &publicElement, bool validateOtherPublicKey, const Integer &privateExponent) const =0;
};

//! interface for key derivation algorithms used in DL cryptosystems
template <class T>
class CRYPTOPP_NO_VTABLE DL_KeyDerivationAlgorithm
{
public:
        virtual bool ParameterSupported(const char *name) const {return false;}
        virtual void Derive(const DL_GroupParameters<T> &groupParams, byte *derivedKey, size_t derivedLength, const T &agreedElement, const T &ephemeralPublicKey, const NameValuePairs &derivationParams) const =0;
};

//! interface for symmetric encryption algorithms used in DL cryptosystems
class CRYPTOPP_NO_VTABLE DL_SymmetricEncryptionAlgorithm
{
public:
        virtual bool ParameterSupported(const char *name) const {return false;}
        virtual size_t GetSymmetricKeyLength(size_t plaintextLength) const =0;
        virtual size_t GetSymmetricCiphertextLength(size_t plaintextLength) const =0;
        virtual size_t GetMaxSymmetricPlaintextLength(size_t ciphertextLength) const =0;
        virtual void SymmetricEncrypt(RandomNumberGenerator &rng, const byte *key, const byte *plaintext, size_t plaintextLength, byte *ciphertext, const NameValuePairs &parameters) const =0;
        virtual DecodingResult SymmetricDecrypt(const byte *key, const byte *ciphertext, size_t ciphertextLength, byte *plaintext, const NameValuePairs &parameters) const =0;
};

//! _
template <class KI>
class CRYPTOPP_NO_VTABLE DL_Base
{
protected:
        typedef KI KeyInterface;
        typedef typename KI::Element Element;

        const DL_GroupParameters<Element> & GetAbstractGroupParameters() const {return GetKeyInterface().GetAbstractGroupParameters();}
        DL_GroupParameters<Element> & AccessAbstractGroupParameters() {return AccessKeyInterface().AccessAbstractGroupParameters();}

        virtual KeyInterface & AccessKeyInterface() =0;
        virtual const KeyInterface & GetKeyInterface() const =0;
};

//! _
template <class INTERFACE, class KEY_INTERFACE>
class CRYPTOPP_NO_VTABLE DL_SignatureSchemeBase : public INTERFACE, public DL_Base<KEY_INTERFACE>
{
public:
        size_t SignatureLength() const
        {
                return GetSignatureAlgorithm().RLen(this->GetAbstractGroupParameters())
                        + GetSignatureAlgorithm().SLen(this->GetAbstractGroupParameters());
        }
        size_t MaxRecoverableLength() const 
                {return GetMessageEncodingInterface().MaxRecoverableLength(0, GetHashIdentifier().second, GetDigestSize());}
        size_t MaxRecoverableLengthFromSignatureLength(size_t signatureLength) const
                {assert(false); return 0;}      // TODO

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

protected:
        size_t MessageRepresentativeLength() const {return BitsToBytes(MessageRepresentativeBitLength());}
        size_t 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 size_t 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, size_t 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);
        }

        size_t 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);

                size_t 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, size_t signatureLength) const
        {
                PK_MessageAccumulatorBase &ma = static_cast<PK_MessageAccumulatorBase &>(messageAccumulator);
                const DL_ElgamalLikeSignatureAlgorithm<T> &alg = this->GetSignatureAlgorithm();
                const DL_GroupParameters<T> &params = this->GetAbstractGroupParameters();

                size_t 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;

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

        size_t CiphertextLength(size_t plaintextLength) const
        {
                size_t 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, size_t 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);
                        size_t 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, size_t 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();
        }
        size_t 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
                {return Singleton<CPP_TYPENAME SCHEME_OPTIONS::KeyAgreementAlgorithm>().Ref();}
        const DL_KeyDerivationAlgorithm<Element> & GetKeyDerivationAlgorithm() const
                {return Singleton<CPP_TYPENAME SCHEME_OPTIONS::KeyDerivationAlgorithm>().Ref();}
        const DL_SymmetricEncryptionAlgorithm & GetSymmetricEncryptionAlgorithm() const
                {return Singleton<CPP_TYPENAME SCHEME_OPTIONS::SymmetricEncryptionAlgorithm>().Ref();}
        HashIdentifier GetHashIdentifier() const
                {return HashIdentifier();}
        const PK_SignatureMessageEncodingMethod & GetMessageEncodingInterface() const 
                {return Singleton<CPP_TYPENAME SCHEME_OPTIONS::MessageEncodingMethod>().Ref();}
};

//! _
template <class SCHEME_OPTIONS>
class DL_SignerImpl : public DL_ObjectImpl<DL_SignerBase<typename SCHEME_OPTIONS::Element>, SCHEME_OPTIONS, typename SCHEME_OPTIONS::PrivateKey>
{
public:
        PK_MessageAccumulator * NewSignatureAccumulator(RandomNumberGenerator &rng) const
        {
                std::auto_ptr<PK_MessageAccumulatorBase> p(new PK_MessageAccumulatorImpl<CPP_TYPENAME SCHEME_OPTIONS::HashFunction>);
                this->RestartMessageAccumulator(rng, *p);
                return p.release();
        }
};

//! _
template <class SCHEME_OPTIONS>
class DL_VerifierImpl : public DL_ObjectImpl<DL_VerifierBase<typename SCHEME_OPTIONS::Element>, SCHEME_OPTIONS, typename SCHEME_OPTIONS::PublicKey>
{
public:
        PK_MessageAccumulator * NewVerificationAccumulator() const
        {
                return new PK_MessageAccumulatorImpl<CPP_TYPENAME SCHEME_OPTIONS::HashFunction>;
        }
};

//! _
template <class SCHEME_OPTIONS>
class DL_EncryptorImpl : public DL_ObjectImpl<DL_EncryptorBase<typename SCHEME_OPTIONS::Element>, SCHEME_OPTIONS, typename SCHEME_OPTIONS::PublicKey>
{
};

//! _
template <class SCHEME_OPTIONS>
class DL_DecryptorImpl : public DL_ObjectImpl<DL_DecryptorBase<typename SCHEME_OPTIONS::Element>, SCHEME_OPTIONS, typename SCHEME_OPTIONS::PrivateKey>
{
};

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

//! _
template <class T>
class CRYPTOPP_NO_VTABLE DL_SimpleKeyAgreementDomainBase : public SimpleKeyAgreementDomain
{
public:
        typedef T Element;

        CryptoParameters & AccessCryptoParameters() {return AccessAbstractGroupParameters();}
        unsigned int AgreedValueLength() const {return GetAbstractGroupParameters().GetEncodedElementSize(false);}
        unsigned int PrivateKeyLength() const {return GetAbstractGroupParameters().GetSubgroupOrder().ByteCount();}
        unsigned int PublicKeyLength() const {return GetAbstractGroupParameters().GetEncodedElementSize(true);}

        void GeneratePrivateKey(RandomNumberGenerator &rng, byte *privateKey) const
        {
                Integer x(rng, Integer::One(), GetAbstractGroupParameters().GetMaxExponent());
                x.Encode(privateKey, PrivateKeyLength());
        }

        void GeneratePublicKey(RandomNumberGenerator &rng, const byte *privateKey, byte *publicKey) const
        {
                const DL_GroupParameters<T> &params = GetAbstractGroupParameters();
                Integer x(privateKey, PrivateKeyLength());
                Element y = params.ExponentiateBase(x);
                params.EncodeElement(true, y, publicKey);
        }
        
        bool Agree(byte *agreedValue, const byte *privateKey, const byte *otherPublicKey, bool validateOtherPublicKey=true) const
        {
                try
                {
                        const DL_GroupParameters<T> &params = GetAbstractGroupParameters();
                        Integer x(privateKey, PrivateKeyLength());
                        Element w = params.DecodeElement(otherPublicKey, validateOtherPublicKey);

                        Element z = GetKeyAgreementAlgorithm().AgreeWithStaticPrivateKey(
                                GetAbstractGroupParameters(), w, validateOtherPublicKey, x);
                        params.EncodeElement(false, z, agreedValue);
                }
                catch (DL_BadElement &)
                {
                        return false;
                }
                return true;
        }

        const Element &GetGenerator() const {return GetAbstractGroupParameters().GetSubgroupGenerator();}

protected:
        virtual const DL_KeyAgreementAlgorithm<Element> & GetKeyAgreementAlgorithm() const =0;
        virtual DL_GroupParameters<Element> & AccessAbstractGroupParameters() =0;
        const DL_GroupParameters<Element> & GetAbstractGroupParameters() const {return const_cast<DL_SimpleKeyAgreementDomainBase<Element> *>(this)->AccessAbstractGroupParameters();}
};

enum CofactorMultiplicationOption {NO_COFACTOR_MULTIPLICTION, COMPATIBLE_COFACTOR_MULTIPLICTION, INCOMPATIBLE_COFACTOR_MULTIPLICTION};
typedef EnumToType<CofactorMultiplicationOption, NO_COFACTOR_MULTIPLICTION> NoCofactorMultiplication;
typedef EnumToType<CofactorMultiplicationOption, COMPATIBLE_COFACTOR_MULTIPLICTION> CompatibleCofactorMultiplication;
typedef EnumToType<CofactorMultiplicationOption, INCOMPATIBLE_COFACTOR_MULTIPLICTION> IncompatibleCofactorMultiplication;

//! DH key agreement algorithm
template <class ELEMENT, class COFACTOR_OPTION>
class DL_KeyAgreementAlgorithm_DH : public DL_KeyAgreementAlgorithm<ELEMENT>
{
public:
        typedef ELEMENT Element;

        static const char * CRYPTOPP_API StaticAlgorithmName()
                {return COFACTOR_OPTION::ToEnum() == INCOMPATIBLE_COFACTOR_MULTIPLICTION ? "DHC" : "DH";}

        Element AgreeWithEphemeralPrivateKey(const DL_GroupParameters<Element> &params, const DL_FixedBasePrecomputation<Element> &publicPrecomputation, const Integer &privateExponent) const
        {
                return publicPrecomputation.Exponentiate(params.GetGroupPrecomputation(), 
                        COFACTOR_OPTION::ToEnum() == INCOMPATIBLE_COFACTOR_MULTIPLICTION ? privateExponent*params.GetCofactor() : privateExponent);
        }

        Element AgreeWithStaticPrivateKey(const DL_GroupParameters<Element> &params, const Element &publicElement, bool validateOtherPublicKey, const Integer &privateExponent) const
        {
                if (COFACTOR_OPTION::ToEnum() == COMPATIBLE_COFACTOR_MULTIPLICTION)
                {
                        const Integer &k = params.GetCofactor();
                        return params.ExponentiateElement(publicElement, 
                                ModularArithmetic(params.GetSubgroupOrder()).Divide(privateExponent, k)*k);
                }
                else if (COFACTOR_OPTION::ToEnum() == INCOMPATIBLE_COFACTOR_MULTIPLICTION)
                        return params.ExponentiateElement(publicElement, privateExponent*params.GetCofactor());
                else
                {
                        assert(COFACTOR_OPTION::ToEnum() == NO_COFACTOR_MULTIPLICTION);

                        if (!validateOtherPublicKey)
                                return params.ExponentiateElement(publicElement, privateExponent);

                        if (params.FastSubgroupCheckAvailable())
                        {
                                if (!params.ValidateElement(2, publicElement, NULL))
                                        throw DL_BadElement();
                                return params.ExponentiateElement(publicElement, privateExponent);
                        }
                        else
                        {
                                const Integer e[2] = {params.GetSubgroupOrder(), privateExponent};
                                Element r[2];
                                params.SimultaneousExponentiate(r, publicElement, e, 2);
                                if (!params.IsIdentity(r[0]))
                                        throw DL_BadElement();
                                return r[1];
                        }
                }
        }
};

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

//! A template implementing constructors for public key algorithm classes
template <class BASE>
class CRYPTOPP_NO_VTABLE PK_FinalTemplate : public BASE
{
public:
        PK_FinalTemplate() {}

        PK_FinalTemplate(const CryptoMaterial &key)
                {this->AccessKey().AssignFrom(key);}

        PK_FinalTemplate(BufferedTransformation &bt)
                {this->AccessKey().BERDecode(bt);}

        PK_FinalTemplate(const AsymmetricAlgorithm &algorithm)
                {this->AccessKey().AssignFrom(algorithm.GetMaterial());}

        PK_FinalTemplate(const Integer &v1)
                {this->AccessKey().Initialize(v1);}

#if (defined(_MSC_VER) && _MSC_VER < 1300)

        template <class T1, class T2>
        PK_FinalTemplate(T1 &v1, T2 &v2)
                {this->AccessKey().Initialize(v1, v2);}

        template <class T1, class T2, class T3>
        PK_FinalTemplate(T1 &v1, T2 &v2, T3 &v3)
                {this->AccessKey().Initialize(v1, v2, v3);}
        
        template <class T1, class T2, class T3, class T4>
        PK_FinalTemplate(T1 &v1, T2 &v2, T3 &v3, T4 &v4)
                {this->AccessKey().Initialize(v1, v2, v3, v4);}

        template <class T1, class T2, class T3, class T4, class T5>
        PK_FinalTemplate(T1 &v1, T2 &v2, T3 &v3, T4 &v4, T5 &v5)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5);}

        template <class T1, class T2, class T3, class T4, class T5, class T6>
        PK_FinalTemplate(T1 &v1, T2 &v2, T3 &v3, T4 &v4, T5 &v5, T6 &v6)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6);}

        template <class T1, class T2, class T3, class T4, class T5, class T6, class T7>
        PK_FinalTemplate(T1 &v1, T2 &v2, T3 &v3, T4 &v4, T5 &v5, T6 &v6, T7 &v7)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6, v7);}

        template <class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8>
        PK_FinalTemplate(T1 &v1, T2 &v2, T3 &v3, T4 &v4, T5 &v5, T6 &v6, T7 &v7, T8 &v8)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6, v7, v8);}

#else

        template <class T1, class T2>
        PK_FinalTemplate(const T1 &v1, const T2 &v2)
                {this->AccessKey().Initialize(v1, v2);}

        template <class T1, class T2, class T3>
        PK_FinalTemplate(const T1 &v1, const T2 &v2, const T3 &v3)
                {this->AccessKey().Initialize(v1, v2, v3);}
        
        template <class T1, class T2, class T3, class T4>
        PK_FinalTemplate(const T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4)
                {this->AccessKey().Initialize(v1, v2, v3, v4);}

        template <class T1, class T2, class T3, class T4, class T5>
        PK_FinalTemplate(const T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4, const T5 &v5)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5);}

        template <class T1, class T2, class T3, class T4, class T5, class T6>
        PK_FinalTemplate(const T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4, const T5 &v5, const T6 &v6)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6);}

        template <class T1, class T2, class T3, class T4, class T5, class T6, class T7>
        PK_FinalTemplate(const T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4, const T5 &v5, const T6 &v6, const T7 &v7)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6, v7);}

        template <class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8>
        PK_FinalTemplate(const T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4, const T5 &v5, const T6 &v6, const T7 &v7, const T8 &v8)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6, v7, v8);}

        template <class T1, class T2>
        PK_FinalTemplate(T1 &v1, const T2 &v2)
                {this->AccessKey().Initialize(v1, v2);}

        template <class T1, class T2, class T3>
        PK_FinalTemplate(T1 &v1, const T2 &v2, const T3 &v3)
                {this->AccessKey().Initialize(v1, v2, v3);}
        
        template <class T1, class T2, class T3, class T4>
        PK_FinalTemplate(T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4)
                {this->AccessKey().Initialize(v1, v2, v3, v4);}

        template <class T1, class T2, class T3, class T4, class T5>
        PK_FinalTemplate(T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4, const T5 &v5)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5);}

        template <class T1, class T2, class T3, class T4, class T5, class T6>
        PK_FinalTemplate(T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4, const T5 &v5, const T6 &v6)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6);}

        template <class T1, class T2, class T3, class T4, class T5, class T6, class T7>
        PK_FinalTemplate(T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4, const T5 &v5, const T6 &v6, const T7 &v7)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6, v7);}

        template <class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8>
        PK_FinalTemplate(T1 &v1, const T2 &v2, const T3 &v3, const T4 &v4, const T5 &v5, const T6 &v6, const T7 &v7, const T8 &v8)
                {this->AccessKey().Initialize(v1, v2, v3, v4, v5, v6, v7, v8);}

#endif
};

//! Base class for public key encryption standard classes. These classes are used to select from variants of algorithms. Note that not all standards apply to all algorithms.
struct EncryptionStandard {};

//! Base class for public key signature standard classes. These classes are used to select from variants of algorithms. Note that not all standards apply to all algorithms.
struct SignatureStandard {};

template <class STANDARD, class KEYS, class ALG_INFO>
class TF_ES;

//! Trapdoor Function Based Encryption Scheme
template <class STANDARD, class KEYS, class ALG_INFO = TF_ES<STANDARD, KEYS, int> >
class TF_ES : public KEYS
{
        typedef typename STANDARD::EncryptionMessageEncodingMethod MessageEncodingMethod;

public:
        //! see EncryptionStandard for a list of standards
        typedef STANDARD Standard;
        typedef TF_CryptoSchemeOptions<ALG_INFO, KEYS, MessageEncodingMethod> SchemeOptions;

        static std::string CRYPTOPP_API StaticAlgorithmName() {return std::string(KEYS::StaticAlgorithmName()) + "/" + MessageEncodingMethod::StaticAlgorithmName();}

        //! implements PK_Decryptor interface
        typedef PK_FinalTemplate<TF_DecryptorImpl<SchemeOptions> > Decryptor;
        //! implements PK_Encryptor interface
        typedef PK_FinalTemplate<TF_EncryptorImpl<SchemeOptions> > Encryptor;
};

template <class STANDARD, class H, class KEYS, class ALG_INFO>  // VC60 workaround: doesn't work if KEYS is first parameter
class TF_SS;

//! Trapdoor Function Based Signature Scheme
template <class STANDARD, class H, class KEYS, class ALG_INFO = TF_SS<STANDARD, H, KEYS, int> > // VC60 workaround: doesn't work if KEYS is first parameter
class TF_SS : public KEYS
{
public:
        //! see SignatureStandard for a list of standards
        typedef STANDARD Standard;
        typedef typename Standard::SignatureMessageEncodingMethod MessageEncodingMethod;
        typedef TF_SignatureSchemeOptions<ALG_INFO, KEYS, MessageEncodingMethod, H> SchemeOptions;

        static std::string CRYPTOPP_API StaticAlgorithmName() {return std::string(KEYS::StaticAlgorithmName()) + "/" + MessageEncodingMethod::StaticAlgorithmName() + "(" + H::StaticAlgorithmName() + ")";}

        //! implements PK_Signer interface
        typedef PK_FinalTemplate<TF_SignerImpl<SchemeOptions> > Signer;
        //! implements PK_Verifier interface
        typedef PK_FinalTemplate<TF_VerifierImpl<SchemeOptions> > Verifier;
};

template <class KEYS, class SA, class MEM, class H, class ALG_INFO>
class DL_SS;

//! Discrete Log Based Signature Scheme
template <class KEYS, class SA, class MEM, class H, class ALG_INFO = DL_SS<KEYS, SA, MEM, H, int> >
class DL_SS : public KEYS
{
        typedef DL_SignatureSchemeOptions<ALG_INFO, KEYS, SA, MEM, H> SchemeOptions;

public:
        static std::string StaticAlgorithmName() {return SA::StaticAlgorithmName() + std::string("/EMSA1(") + H::StaticAlgorithmName() + ")";}

        //! implements PK_Signer interface
        typedef PK_FinalTemplate<DL_SignerImpl<SchemeOptions> > Signer;
        //! implements PK_Verifier interface
        typedef PK_FinalTemplate<DL_VerifierImpl<SchemeOptions> > Verifier;
};

//! Discrete Log Based Encryption Scheme
template <class KEYS, class AA, class DA, class EA, class ALG_INFO>
class DL_ES : public KEYS
{
        typedef DL_CryptoSchemeOptions<ALG_INFO, KEYS, AA, DA, EA> SchemeOptions;

public:
        //! implements PK_Decryptor interface
        typedef PK_FinalTemplate<DL_DecryptorImpl<SchemeOptions> > Decryptor;
        //! implements PK_Encryptor interface
        typedef PK_FinalTemplate<DL_EncryptorImpl<SchemeOptions> > Encryptor;
};

NAMESPACE_END

#endif

---