rng.cpp

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

#include "pch.h"

#include "rng.h"
#include "fips140.h"

#include <time.h>
#include <math.h>

NAMESPACE_BEGIN(CryptoPP)

// linear congruential generator
// originally by William S. England

// do not use for cryptographic purposes

/*
** Original_numbers are the original published m and q in the
** ACM article above.  John Burton has furnished numbers for
** a reportedly better generator.  The new numbers are now
** used in this program by default.
*/

#ifndef LCRNG_ORIGINAL_NUMBERS
const word32 LC_RNG::m=2147483647L;
const word32 LC_RNG::q=44488L;

const word16 LC_RNG::a=(unsigned int)48271L;
const word16 LC_RNG::r=3399;
#else
const word32 LC_RNG::m=2147483647L;
const word32 LC_RNG::q=127773L;

const word16 LC_RNG::a=16807;
const word16 LC_RNG::r=2836;
#endif

void LC_RNG::GenerateBlock(byte *output, size_t size)
{
    while (size--)
    {
        word32 hi = seed/q;
        word32 lo = seed%q;

        long test = a*lo - r*hi;

        if (test > 0)
            seed = test;
        else
            seed = test+ m;

        *output++ = byte((GETBYTE(seed, 0) ^ GETBYTE(seed, 1) ^ GETBYTE(seed, 2) ^ GETBYTE(seed, 3)));
    }
}

// ********************************************************

#ifndef CRYPTOPP_IMPORTS

X917RNG::X917RNG(BlockTransformation *c, const byte *seed, const byte *deterministicTimeVector)
    : m_cipher(c),
      m_size(m_cipher->BlockSize()),
      m_datetime(m_size),
      m_randseed(seed, m_size),
      m_lastBlock(m_size),
      m_deterministicTimeVector(deterministicTimeVector, deterministicTimeVector ? m_size : 0)
{
    // Valgrind finding, http://github.com/weidai11/cryptopp/issues/105
    // Garbage in the tail creates a non-conforming X9.17 or X9.31 generator.
    if (m_size > 8)
    {
        memset(m_datetime, 0x00, m_size);
        memset(m_lastBlock, 0x00, m_size);
    }

    if (!deterministicTimeVector)
    {
        time_t tstamp1 = ::time(NULLPTR);
        xorbuf(m_datetime, (byte *)&tstamp1, UnsignedMin(sizeof(tstamp1), m_size));
        m_cipher->ProcessBlock(m_datetime);
        clock_t tstamp2 = clock();
        xorbuf(m_datetime, (byte *)&tstamp2, UnsignedMin(sizeof(tstamp2), m_size));
        m_cipher->ProcessBlock(m_datetime);
    }

    // for FIPS 140-2
    // GenerateBlock(m_lastBlock, m_size);

    // Make explicit call to avoid virtual-dispatch findings in ctor
    ArraySink target(m_lastBlock, m_size);
    X917RNG::GenerateIntoBufferedTransformation(target, DEFAULT_CHANNEL, m_size);
}

void X917RNG::GenerateIntoBufferedTransformation(BufferedTransformation &target, const std::string &channel, lword size)
{
    while (size > 0)
    {
        // calculate new enciphered timestamp
        if (m_deterministicTimeVector.size())
        {
            m_cipher->ProcessBlock(m_deterministicTimeVector, m_datetime);
            IncrementCounterByOne(m_deterministicTimeVector, m_size);
        }
        else
        {
            clock_t c = clock();
            xorbuf(m_datetime, (byte *)&c, UnsignedMin(sizeof(c), m_size));
            time_t t = ::time(NULLPTR);
            xorbuf(m_datetime+m_size-UnsignedMin(sizeof(t), m_size), (byte *)&t, UnsignedMin(sizeof(t), m_size));
            m_cipher->ProcessBlock(m_datetime);
        }

        // combine enciphered timestamp with seed
        xorbuf(m_randseed, m_datetime, m_size);

        // generate a new block of random bytes
        m_cipher->ProcessBlock(m_randseed);
        if (memcmp(m_lastBlock, m_randseed, m_size) == 0)
            throw SelfTestFailure("X917RNG: Continuous random number generator test failed.");

        // output random bytes
        size_t len = UnsignedMin(m_size, size);
        target.ChannelPut(channel, m_randseed, len);
        size -= len;

        // compute new seed vector
        memcpy(m_lastBlock, m_randseed, m_size);
        xorbuf(m_randseed, m_datetime, m_size);
        m_cipher->ProcessBlock(m_randseed);
    }
}

#endif

MaurerRandomnessTest::MaurerRandomnessTest()
    : sum(0.0), n(0)
{
    for (unsigned i=0; i<V; i++)
        tab[i] = 0;
}

size_t MaurerRandomnessTest::Put2(const byte *inString, size_t length, int /*messageEnd*/, bool /*blocking*/)
{
    while (length--)
    {
        byte inByte = *inString++;
        if (n >= Q)
            sum += ::log(double(n - tab[inByte]));
        tab[inByte] = n;
        n++;
    }
    return 0;
}

double MaurerRandomnessTest::GetTestValue() const
{
    if (BytesNeeded() > 0)
        throw Exception(Exception::OTHER_ERROR, "MaurerRandomnessTest: " + IntToString(BytesNeeded()) + " more bytes of input needed");

    double fTu = (sum/(n-Q))/::log(2.0);    // this is the test value defined by Maurer

    double value = fTu * 0.1392;        // arbitrarily normalize it to
    return value > 1.0 ? 1.0 : value;   // a number between 0 and 1
}

NAMESPACE_END