pssr.h

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

/// \file pssr.h
/// \brief Classes for probablistic signature schemes
/// \since Crypto++ 2.1

#ifndef CRYPTOPP_PSSR_H
#define CRYPTOPP_PSSR_H

#include "cryptlib.h"
#include "pubkey.h"
#include "emsa2.h"

#ifdef CRYPTOPP_IS_DLL
#include "sha.h"
#endif

NAMESPACE_BEGIN(CryptoPP)

/// \brief PSSR Message Encoding Method interface
/// \since Crypto++ 2.1
class CRYPTOPP_DLL PSSR_MEM_Base : public PK_RecoverableSignatureMessageEncodingMethod
{
public:
    virtual ~PSSR_MEM_Base() {}

protected:
    virtual bool AllowRecovery() const =0;
    virtual size_t SaltLen(size_t hashLen) const =0;
    virtual size_t MinPadLen(size_t hashLen) const =0;
    virtual const MaskGeneratingFunction & GetMGF() const =0;

private:
    size_t MinRepresentativeBitLength(size_t hashIdentifierLength, size_t digestLength) const;
    size_t MaxRecoverableLength(size_t representativeBitLength, size_t hashIdentifierLength, size_t digestLength) const;
    bool IsProbabilistic() const;
    bool AllowNonrecoverablePart() const;
    bool RecoverablePartFirst() const;
    void ComputeMessageRepresentative(RandomNumberGenerator &rng,
        const byte *recoverableMessage, size_t recoverableMessageLength,
        HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
        byte *representative, size_t representativeBitLength) const;
    DecodingResult RecoverMessageFromRepresentative(
        HashTransformation &hash, HashIdentifier hashIdentifier, bool messageEmpty,
        byte *representative, size_t representativeBitLength,
        byte *recoverableMessage) const;
};

/// \brief PSSR Message Encoding Method with Hash Identifier
/// \tparam USE_HASH_ID flag indicating whether the HashId is used
/// \since Crypto++ 2.1
template <bool USE_HASH_ID> class PSSR_MEM_BaseWithHashId;

/// \brief PSSR Message Encoding Method with Hash Identifier
/// \details If USE_HASH_ID is true, then EMSA2HashIdLookup<PSSR_MEM_Base> is used for the base class
template<> class PSSR_MEM_BaseWithHashId<true> : public EMSA2HashIdLookup<PSSR_MEM_Base> {};

/// \brief PSSR Message Encoding Method without Hash Identifier
/// \details If USE_HASH_ID is false, then PSSR_MEM_Base is used for the base class
/// \since Crypto++ 2.1
template<> class PSSR_MEM_BaseWithHashId<false> : public PSSR_MEM_Base {};

/// \brief PSSR Message Encoding Method
/// \tparam ALLOW_RECOVERY flag indicating whether the scheme provides message recovery
/// \tparam MGF mask generation function
/// \tparam SALT_LEN length of the salt
/// \tparam MIN_PAD_LEN minimum length of the pad
/// \tparam USE_HASH_ID flag indicating whether the HashId is used
/// \details If ALLOW_RECOVERY is true, the the signature scheme provides message recovery. If
///  ALLOW_RECOVERY is false, the the signature scheme is appendix, and the message must be
///  provided during verification.
/// \since Crypto++ 2.1
template <bool ALLOW_RECOVERY, class MGF=P1363_MGF1, int SALT_LEN=-1, int MIN_PAD_LEN=0, bool USE_HASH_ID=false>
class PSSR_MEM : public PSSR_MEM_BaseWithHashId<USE_HASH_ID>
{
    virtual bool AllowRecovery() const {return ALLOW_RECOVERY;}
    virtual size_t SaltLen(size_t hashLen) const {return SALT_LEN < 0 ? hashLen : SALT_LEN;}
    virtual size_t MinPadLen(size_t hashLen) const {return MIN_PAD_LEN < 0 ? hashLen : MIN_PAD_LEN;}
    virtual const MaskGeneratingFunction & GetMGF() const {static MGF mgf; return mgf;}

public:
    static std::string CRYPTOPP_API StaticAlgorithmName() {return std::string(ALLOW_RECOVERY ? "PSSR-" : "PSS-") + MGF::StaticAlgorithmName();}
};

/// \brief Probabilistic Signature Scheme with Recovery
/// \details Signature Schemes with Recovery encode the message with the signature.
/// \sa <a href="http://www.weidai.com/scan-mirror/sig.html#sem_PSSR-MGF1">PSSR-MGF1</a>
/// \since Crypto++ 2.1
struct PSSR : public SignatureStandard
{
    typedef PSSR_MEM<true> SignatureMessageEncodingMethod;
};

/// \brief Probabilistic Signature Scheme with Appendix
/// \details Signature Schemes with Appendix require the message to be provided during verification.
/// \sa <a href="http://www.weidai.com/scan-mirror/sig.html#sem_PSS-MGF1">PSS-MGF1</a>
/// \since Crypto++ 2.1
struct PSS : public SignatureStandard
{
    typedef PSSR_MEM<false> SignatureMessageEncodingMethod;
};

NAMESPACE_END

#endif