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

/// \file rng.h

/// \brief Miscellaneous classes for RNGs

/// \details This file contains miscellaneous classes for RNGs, including LC_RNG(),

///  X917RNG() and MaurerRandomnessTest()

/// \sa osrng.h, randpool.h

#ifndef CRYPTOPP_RNG_H

#define CRYPTOPP_RNG_H

#include "cryptlib.h"

#include "filters.h"

#include "smartptr.h"

NAMESPACE_BEGIN(CryptoPP)

/// \brief Linear Congruential Generator (LCG)

/// \details Originally propsed by William S. England.

/// \warning LC_RNG is suitable for simulations, where uniformaly distributed numbers are

///  required quickly. It should not be used for cryptographic purposes.

class LC_RNG : public RandomNumberGenerator

{

public:

  /// \brief Construct a Linear Congruential Generator (LCG)

  /// \param init_seed the initial value for the generator

  LC_RNG(word32 init_seed)

    : seed(init_seed) {}

  void GenerateBlock(byte *output, size_t size);

  word32 GetSeed() {return seed;}

private:

  word32 seed;

  static const word32 m;

  static const word32 q;

  static const word16 a;

  static const word16 r;

};

/// \brief ANSI X9.17 RNG

/// \details X917RNG is from ANSI X9.17 Appendix C, and it uses a 64-bit block cipher, like TripleDES.

///  If you use a 128-bit block cipher, like AES, then you are effectively using an ANSI X9.31 generator.

/// \details You should reseed the generator after a fork() to avoid multiple generators

///  with the same internal state.

/// \sa AutoSeededX917RNG, DefaultAutoSeededRNG

class CRYPTOPP_DLL X917RNG : public RandomNumberGenerator, public NotCopyable

{

public:

  /// \brief Construct a X917RNG

  /// \param cipher the block cipher to use for the generator

  /// \param seed a byte buffer to use as a seed

  /// \param deterministicTimeVector additional entropy

  /// \details <tt>cipher</tt> will be deleted by the destructor. <tt>seed</tt> must be at least

  ///  BlockSize() in length. <tt>deterministicTimeVector = 0</tt> means obtain time vector

  ///  from the system.

  /// \details When constructing a X917RNG, the generator must be keyed or an access

  ///  violation will occur because the time vector is encrypted using the block cipher.

  ///  To key the generator during constructions, perform the following:

  /// <pre>

  ///  SecByteBlock key(AES::DEFAULT_KEYLENGTH), seed(AES::BLOCKSIZE);

  ///  OS_GenerateRandomBlock(false, key, key.size());

  ///  OS_GenerateRandomBlock(false, seed, seed.size());

  ///  X917RNG prng(new AES::Encryption(key, AES::DEFAULT_KEYLENGTH), seed, NULLPTR);</pre>

  /// \sa AutoSeededX917RNG

  X917RNG(BlockTransformation *cipher, const byte *seed, const byte *deterministicTimeVector = NULLPTR);

  void GenerateIntoBufferedTransformation(BufferedTransformation &target, const std::string &channel, lword size);

private:

  member_ptr<BlockTransformation> m_cipher;

  const unsigned int m_size;  // S, blocksize of cipher

  SecByteBlock m_datetime;    // DT, buffer for enciphered timestamp

  SecByteBlock m_randseed, m_lastBlock, m_deterministicTimeVector;

};

/// \brief  Maurer's Universal Statistical Test for Random Bit Generators

/// \details This class implements Maurer's Universal Statistical Test for

///  Random Bit Generators. It is intended for measuring the randomness of

///  *PHYSICAL* RNGs.

/// \details For more details see Maurer's paper in Journal of Cryptology, 1992.

class MaurerRandomnessTest : public Bufferless<Sink>

{

public:

  /// \brief Construct a MaurerRandomnessTest

  MaurerRandomnessTest();

  size_t Put2(const byte *inString, size_t length, int messageEnd, bool blocking);

  /// \brief Provides the number of bytes of input is needed by the test

  /// \return how many more bytes of input is needed by the test

  // BytesNeeded() returns how many more bytes of input is needed by the test

  // GetTestValue() should not be called before BytesNeeded()==0

  unsigned int BytesNeeded() const {return n >= (Q+K) ? 0 : Q+K-n;}

  // returns a number between 0.0 and 1.0, describing the quality of the

  // random numbers entered

  double GetTestValue() const;

private:

  enum {L=8, V=256, Q=2000, K=2000};

  double sum;

  unsigned int n;

  unsigned int tab[V];

};

NAMESPACE_END

#endif