rng.h

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// 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 distrubuted 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.
/// \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
    /// \returns 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