source: git/src-cryptopp/rw.h

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

//! \file rw.h
//! \brief Classes for Rabin-Williams signature scheme
//! \details The implementation provides Rabin-Williams signature schemes as defined in
//!   IEEE P1363. It uses Bernstein's tweaked square roots in place of square roots to
//!   speedup calculations.
//! \sa <A HREF="http://cr.yp.to/sigs/rwsota-20080131.pdf">RSA signatures and Rabin–Williams
//!   signatures: the state of the art (20080131)</A>, Section 6, <em>The tweaks e and f</em>.

#ifndef CRYPTOPP_RW_H
#define CRYPTOPP_RW_H

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

NAMESPACE_BEGIN(CryptoPP)

//! \class RWFunction
//! \brief Rabin-Williams trapdoor function using the public key
class CRYPTOPP_DLL RWFunction : public TrapdoorFunction, public PublicKey
{
        typedef RWFunction ThisClass;

public:
        void Initialize(const Integer &n)
                {m_n = n;}

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

        void Save(BufferedTransformation &bt) const
                {DEREncode(bt);}
        void Load(BufferedTransformation &bt)
                {BERDecode(bt);}

        Integer ApplyFunction(const Integer &x) const;
        Integer PreimageBound() const {return ++(m_n>>1);}
        Integer ImageBound() const {return m_n;}

        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);

        const Integer& GetModulus() const {return m_n;}
        void SetModulus(const Integer &n) {m_n = n;}

protected:
        Integer m_n;
};

//! \class InvertibleRWFunction
//! \brief Rabin-Williams trapdoor function using the private key
//! \since Tweaked roots using <em>e</em> and <em>f</em> since Crypto++ 5.6.4
class CRYPTOPP_DLL InvertibleRWFunction : public RWFunction, public TrapdoorFunctionInverse, public PrivateKey
{
        typedef InvertibleRWFunction ThisClass;

public:
        InvertibleRWFunction() : m_precompute(false) {}

        void Initialize(const Integer &n, const Integer &p, const Integer &q, const Integer &u);
        // generate a random private key
        void Initialize(RandomNumberGenerator &rng, unsigned int modulusBits)
                {GenerateRandomWithKeySize(rng, modulusBits);}

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

        void Save(BufferedTransformation &bt) const
                {DEREncode(bt);}
        void Load(BufferedTransformation &bt)
                {BERDecode(bt);}

        Integer CalculateInverse(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;}
        const Integer& GetMultiplicativeInverseOfPrime2ModPrime1() const {return m_u;}

        void SetPrime1(const Integer &p) {m_p = p;}
        void SetPrime2(const Integer &q) {m_q = q;}
        void SetMultiplicativeInverseOfPrime2ModPrime1(const Integer &u) {m_u = u;}

        virtual bool SupportsPrecomputation() const {return true;}
        virtual void Precompute(unsigned int unused = 0) {CRYPTOPP_UNUSED(unused); PrecomputeTweakedRoots();}
        virtual void Precompute(unsigned int unused = 0) const {CRYPTOPP_UNUSED(unused); PrecomputeTweakedRoots();}

        virtual void LoadPrecomputation(BufferedTransformation &storedPrecomputation);
        virtual void SavePrecomputation(BufferedTransformation &storedPrecomputation) const;

protected:
        void PrecomputeTweakedRoots() const;

protected:
        Integer m_p, m_q, m_u;

        mutable Integer m_pre_2_9p, m_pre_2_3q, m_pre_q_p;
        mutable bool m_precompute;
};

//! \class RW
//! \brief Rabin-Williams algorithm
struct RW
{
        static std::string StaticAlgorithmName() {return "RW";}
        typedef RWFunction PublicKey;
        typedef InvertibleRWFunction PrivateKey;
};

//! \class RWSS
//! \brief Rabin-Williams signature scheme
template <class STANDARD, class H>
struct RWSS : public TF_SS<STANDARD, H, RW>
{
};

NAMESPACE_END

#endif