esign.h

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


#ifndef CRYPTOPP_ESIGN_H
#define CRYPTOPP_ESIGN_H

#include "cryptlib.h"
#include "pubkey.h"
#include "integer.h"
#include "asn.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

class ESIGNFunction : public TrapdoorFunction, public ASN1CryptoMaterial<PublicKey>
{
        typedef ESIGNFunction ThisClass;

public:

        void Initialize(const Integer &n, const Integer &e)
                {m_n = n; m_e = e;}

        // PublicKey
        void BERDecode(BufferedTransformation &bt);
        void DEREncode(BufferedTransformation &bt) const;

        // CryptoMaterial
        bool Validate(RandomNumberGenerator &rng, unsigned int level) const;
        bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const;
        void AssignFrom(const NameValuePairs &source);

        // TrapdoorFunction
        Integer ApplyFunction(const Integer &x) const;
        Integer PreimageBound() const {return m_n;}
        Integer ImageBound() const {return Integer::Power2(GetK());}

        // non-derived
        const Integer & GetModulus() const {return m_n;}
        const Integer & GetPublicExponent() const {return m_e;}

        void SetModulus(const Integer &n) {m_n = n;}
        void SetPublicExponent(const Integer &e) {m_e = e;}

protected:
        // Covertiy finding on overflow. The library allows small values for research purposes.
        unsigned int GetK() const {return SaturatingSubtract(m_n.BitCount()/3, 1U);}

        Integer m_n, m_e;
};

class InvertibleESIGNFunction : public ESIGNFunction, public RandomizedTrapdoorFunctionInverse, public PrivateKey
{
        typedef InvertibleESIGNFunction ThisClass;

public:

        void Initialize(const Integer &n, const Integer &e, const Integer &p, const Integer &q)
                {m_n = n; m_e = e; m_p = p; m_q = q;}

        void Initialize(RandomNumberGenerator &rng, unsigned int modulusBits)
                {GenerateRandomWithKeySize(rng, modulusBits);}

        void BERDecode(BufferedTransformation &bt);
        void DEREncode(BufferedTransformation &bt) const;

        Integer CalculateRandomizedInverse(RandomNumberGenerator &rng, const Integer &x) const;

        // GeneratibleCryptoMaterial
        bool Validate(RandomNumberGenerator &rng, unsigned int level) const;
        bool GetVoidValue(const char *name, const std::type_info &valueType, void *pValue) const;
        void AssignFrom(const NameValuePairs &source);
        void GenerateRandom(RandomNumberGenerator &rng, const NameValuePairs &alg);

        const Integer& GetPrime1() const {return m_p;}
        const Integer& GetPrime2() const {return m_q;}

        void SetPrime1(const Integer &p) {m_p = p;}
        void SetPrime2(const Integer &q) {m_q = q;}

protected:
        Integer m_p, m_q;
};

template <class T>
class EMSA5Pad : public PK_DeterministicSignatureMessageEncodingMethod
{
public:
        CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() {return "EMSA5";}

        void ComputeMessageRepresentative(RandomNumberGenerator &rng,
                const byte *recoverableMessage, size_t recoverableMessageLength,
                HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
                byte *representative, size_t representativeBitLength) const
        {
                CRYPTOPP_UNUSED(rng), CRYPTOPP_UNUSED(recoverableMessage), CRYPTOPP_UNUSED(recoverableMessageLength);
                CRYPTOPP_UNUSED(messageEmpty), CRYPTOPP_UNUSED(hashIdentifier);
                SecByteBlock digest(hash.DigestSize());
                hash.Final(digest);
                size_t representativeByteLength = BitsToBytes(representativeBitLength);
                T mgf;
                mgf.GenerateAndMask(hash, representative, representativeByteLength, digest, digest.size(), false);
                if (representativeBitLength % 8 != 0)
                        representative[0] = (byte)Crop(representative[0], representativeBitLength % 8);
        }
};

struct P1363_EMSA5 : public SignatureStandard
{
        typedef EMSA5Pad<P1363_MGF1> SignatureMessageEncodingMethod;
};

struct ESIGN_Keys
{
        CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() {return "ESIGN";}
        typedef ESIGNFunction PublicKey;
        typedef InvertibleESIGNFunction PrivateKey;
};

template <class H, class STANDARD = P1363_EMSA5>
struct ESIGN : public TF_SS<ESIGN_Keys, STANDARD, H>
{
};

NAMESPACE_END

#endif