selgamal.h

伯克利做的SFTP安全文件传输协议

// selgamal.h
// Scott McPeak's re-implementation of ElGamal using crypto++ Integers
// copyright SafeTP Development Group, Inc., 2000  Terms of use are as specified in license.txt

#ifndef __SELGAMAL_H
#define __SELGAMAL_H

#include "trans.h"               // Trans
#include "integer.h"             // Integer

class RandomNumberGenerator;     // cryptlib.h

// hardcoded parameters ([0] is p, [1] is g, in ascii decimal)
extern char const * const ElGamal_512bit_parameters[2];
extern char const * const ElGamal_1024bit_parameters[2];
extern char const * const ElGamal_1536bit_parameters[2];
extern char const * const ElGamal_2048bit_parameters[2];


// raw encrypt and decrypt functions
void ElGamal_encrypt(
  Integer &a, Integer &b,               // output ciphertext
  Integer const &p, Integer const &g,   // parameters
  Integer const &y,                     // public key
  Integer const &message,               // message < p
  RandomNumberGenerator &rng);          // for choosing k

void ElGamal_decrypt(
  Integer &message,                     // output plaintext
  Integer const &p, Integer const &g,   // parameters
  Integer const &x,                     // private key
  Integer const &a, Integer const &b);  // ciphertext

void ElGamal_keygen(
  Integer &x, Integer &y,               // output keys
  Integer const &p, Integer const &g,   // parameters
  RandomNumberGenerator &rng);          // for choosing x


// storage and retrieval of cryptosystem parameters
class ElGamalParameters {
protected:
  Integer p, g;                  // system parameters

public:
  ElGamalParameters(ElGamalParameters const &obj);
  ElGamalParameters(Integer const &p, Integer const &g);
  ElGamalParameters(char const * const *params);     // format of parameters above
  ~ElGamalParameters();

  // encode and decode
  void encode(DataBlock &stream) const;
  ElGamalParameters(DataBlock &stream);

  // selectors
  Integer const &getP() const { return p; }
  Integer const &getG() const { return g; }
};


// public key storage and retrieval
class ElGamalPublicKey : public ElGamalParameters {
protected:
  Integer y;                     // public key

public:
  ElGamalPublicKey(ElGamalPublicKey const &obj);
  ElGamalPublicKey(Integer const &p, Integer const &g, Integer const &y);
  ElGamalPublicKey(ElGamalParameters const &params, Integer const &y);
  ~ElGamalPublicKey();

  // encode / decode
  void encode(DataBlock &stream) const;
  ElGamalPublicKey(DataBlock &stream);

  // selectors
  Integer const &getY() const { return y; }
};


// transformation interface for encryption
class ElGamalEncryptor : public Trans, public ElGamalPublicKey {
  RandomNumberGenerator &rng;    // source of randomness

private:
  void selfCheck();

public:
  ElGamalEncryptor(Integer const &p, Integer const &g, Integer const &y,
                   RandomNumberGenerator &rng);
  ElGamalEncryptor(ElGamalPublicKey const &key, RandomNumberGenerator &rng);
  virtual ~ElGamalEncryptor();

  // decode (encode is same as ElGamalPublicKey)
  ElGamalEncryptor(DataBlock &stream, RandomNumberGenerator &rng);

  // Trans interface
  virtual int minInputSize() const;
  virtual int maxInputSize() const;
  virtual int minOutputSize(int inputSize) const;
  virtual int maxOutputSize(int inputSize) const;
  virtual void trans(DataBlock &data);
};


// private key storage and retrieval
class ElGamalPrivateKey : public ElGamalPublicKey {
protected:
  Integer x;              // private key

public:
  ElGamalPrivateKey(ElGamalPrivateKey const &obj);
  ElGamalPrivateKey(Integer const &p, Integer const &g,
                    Integer const &y, Integer const &x);
  ElGamalPrivateKey(ElGamalPublicKey const &pubkey,
                    Integer const &x);
  ElGamalPrivateKey(ElGamalParameters const &params,
                    RandomNumberGenerator &rng);    // make up a new key pair
  ~ElGamalPrivateKey();

  // encode / decode
  void encode(DataBlock &stream) const;
  ElGamalPrivateKey(DataBlock &stream);

  // selectors
  Integer const &getX() const;
};


// decryption as transformation
class ElGamalDecryptor : public Trans, public ElGamalPrivateKey {
public:
  ElGamalDecryptor(Integer const &p, Integer const &g,
                   Integer const &y, Integer const &x);
  ElGamalDecryptor(ElGamalPrivateKey const &privkey);
  ~ElGamalDecryptor();

  // decode
  ElGamalDecryptor(DataBlock &stream);

  // Trans interface
  virtual int minInputSize() const;
  virtual int maxInputSize() const;
  virtual int minOutputSize(int inputSize) const;
  virtual int maxOutputSize(int inputSize) const;
  virtual void trans(DataBlock &data);
};

#endif // __SELGAMAL_H