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

/// \file oaep.h

/// \brief Classes for optimal asymmetric encryption padding

/// \since Crypto++ 2.1

#ifndef CRYPTOPP_OAEP_H

#define CRYPTOPP_OAEP_H

#include "cryptlib.h"

#include "pubkey.h"

#include "sha.h"

NAMESPACE_BEGIN(CryptoPP)

/// \brief OAEP padding base class

/// \since Crypto++ 2.1

class CRYPTOPP_DLL OAEP_Base : public PK_EncryptionMessageEncodingMethod

{

public:

  bool ParameterSupported(const char *name) const {return strcmp(name, Name::EncodingParameters()) == 0;}

  size_t MaxUnpaddedLength(size_t paddedLength) const;

  void Pad(RandomNumberGenerator &rng, const byte *raw, size_t inputLength, byte *padded, size_t paddedLength, const NameValuePairs &parameters) const;

  DecodingResult Unpad(const byte *padded, size_t paddedLength, byte *raw, const NameValuePairs &parameters) const;

protected:

  virtual unsigned int DigestSize() const =0;

  virtual HashTransformation * NewHash() const =0;

  virtual MaskGeneratingFunction * NewMGF() const =0;

};

/// \brief OAEP padding

/// \tparam H HashTransformation derived class

/// \tparam MGF MaskGeneratingFunction derived class

/// \sa <a href="http://www.weidai.com/scan-mirror/ca.html#cem_OAEP-MGF1">EME-OAEP</a>, for use with classes derived from TF_ES

/// \since Crypto++ 2.1

template <class H, class MGF=P1363_MGF1>

class OAEP : public OAEP_Base, public EncryptionStandard

{

public:

  static std::string CRYPTOPP_API StaticAlgorithmName() {return std::string("OAEP-") + MGF::StaticAlgorithmName() + "(" + H::StaticAlgorithmName() + ")";}

  typedef OAEP<H, MGF> EncryptionMessageEncodingMethod;

protected:

  unsigned int DigestSize() const {return H::DIGESTSIZE;}

  HashTransformation * NewHash() const {return new H;}

  MaskGeneratingFunction * NewMGF() const {return new MGF;}

};

CRYPTOPP_DLL_TEMPLATE_CLASS OAEP<SHA1>;

NAMESPACE_END

#endif