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// rw.h - originally 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
//! \since Crypto++ 2.0, Tweaked roots using <em>e</em> and <em>f</em> since Crypto++ 5.6.4
class CRYPTOPP_DLL RWFunction : public TrapdoorFunction, public PublicKey
{
typedef RWFunction ThisClass;
public:
//! \brief Initialize a Rabin-Williams public key
//! \param n the modulus
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 Crypto++ 2.0, 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:
//! \brief Construct an InvertibleRWFunction
InvertibleRWFunction() : m_precompute(false) {}
//! \brief Initialize a Rabin-Williams private key
//! \param n modulus
//! \param p first prime factor
//! \param q second prime factor
//! \param u q<sup>-1</sup> mod p
//! \details This Initialize() function overload initializes a private key from existing parameters.
void Initialize(const Integer &n, const Integer &p, const Integer &q, const Integer &u);
//! \brief Create a Rabin-Williams private key
//! \param rng a RandomNumberGenerator derived class
//! \param modulusBits the size of the modulus, 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);}
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;
};
//! \brief Rabin-Williams keys
struct RW
{
CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() {return "RW";}
typedef RWFunction PublicKey;
typedef InvertibleRWFunction PrivateKey;
};
//! \brief Rabin-Williams signature scheme
//! \tparam STANDARD signature standard
//! \tparam H hash transformation
template <class STANDARD, class H>
struct RWSS : public TF_SS<RW, STANDARD, H>
{
};
NAMESPACE_END
#endif
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