rng.cpp

Go to the documentation of this file.

// rng.cpp - 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(0);
                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);
}

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(NULL);
                        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