esign.h

Go to the documentation of this file.

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

/// \file esign.h
/// \brief Classes providing ESIGN signature schemes as defined in IEEE P1363a
/// \since Crypto++ 5.0

#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)

/// \brief ESIGN trapdoor function using the public key
/// \since Crypto++ 5.0
class ESIGNFunction : public TrapdoorFunction, public ASN1CryptoMaterial<PublicKey>
{
    typedef ESIGNFunction ThisClass;

public:

    /// \brief Initialize a ESIGN public key with {n,e}
    /// \param n the modulus
    /// \param e the public exponent
    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;
};

/// \brief ESIGN trapdoor function using the private key
/// \since Crypto++ 5.0
class InvertibleESIGNFunction : public ESIGNFunction, public RandomizedTrapdoorFunctionInverse, public PrivateKey
{
    typedef InvertibleESIGNFunction ThisClass;

public:

    /// \brief Initialize a ESIGN private key with {n,e,p,q}
    /// \param n modulus
    /// \param e public exponent
    /// \param p first prime factor
    /// \param q second prime factor
    /// \details This Initialize() function overload initializes a private key from existing parameters.
    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;}

    /// \brief Create a ESIGN private key
    /// \param rng a RandomNumberGenerator derived class
    /// \param modulusBits the size of the modulud, in bits
    /// \details This function overload of Initialize() creates a new private key because it
    ///   takes a RandomNumberGenerator() as a parameter. If you have an existing keypair,
    ///   then use one of the other Initialize() overloads.
    void Initialize(RandomNumberGenerator &rng, unsigned int modulusBits)
        {GenerateRandomWithKeySize(rng, modulusBits);}

    // Squash Visual Studio C4250 warning
    void Save(BufferedTransformation &bt) const
        {BEREncode(bt);}

    // Squash Visual Studio C4250 warning
    void Load(BufferedTransformation &bt)
        {BERDecode(bt);}

    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);
    /*! parameters: (ModulusSize) */
    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;
};

/// \brief EMSA5 padding method
/// \tparam T Mask Generation Function
/// \since Crypto++ 5.0
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);
    }
};

/// \brief EMSA5 padding method, for use with ESIGN
/// \since Crypto++ 5.0
struct P1363_EMSA5 : public SignatureStandard
{
    typedef EMSA5Pad<P1363_MGF1> SignatureMessageEncodingMethod;
};

/// \brief ESIGN keys
/// \since Crypto++ 5.0
struct ESIGN_Keys
{
    CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() {return "ESIGN";}
    typedef ESIGNFunction PublicKey;
    typedef InvertibleESIGNFunction PrivateKey;
};

/// \brief ESIGN signature scheme, IEEE P1363a
/// \tparam H HashTransformation derived class
/// \tparam STANDARD Signature encoding method
/// \since Crypto++ 5.0
template <class H, class STANDARD = P1363_EMSA5>
struct ESIGN : public TF_SS<ESIGN_Keys, STANDARD, H>
{
};

NAMESPACE_END

#endif