randpool.cpp

// randpool.cpp - written and placed in the public domain by Wei Dai
// The algorithm in this module comes from PGP's randpool.c

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "randpool.h"
#include "mdc.h"
#include "sha.h"
#include "modes.h"

NAMESPACE_BEGIN(CryptoPP)

typedef MDC<SHA> RandomPoolCipher;

RandomPool::RandomPool(unsigned int poolSize)
        : pool(poolSize), key(RandomPoolCipher::DEFAULT_KEYLENGTH)
{
        assert(poolSize > key.size());

        addPos=0;
        getPos=poolSize;
        memset(pool, 0, poolSize);
        memset(key, 0, key.size());
}

void RandomPool::Stir()
{
        CFB_Mode<RandomPoolCipher>::Encryption cipher;

        for (int i=0; i<2; i++)
        {
                cipher.SetKeyWithIV(key, key.size(), pool.end()-cipher.IVSize());
                cipher.ProcessString(pool, pool.size());
                memcpy(key, pool, key.size());
        }

        addPos = 0;
        getPos = key.size();
}

size_t RandomPool::Put2(const byte *inString, size_t length, int messageEnd, bool blocking)
{
        size_t t;

        while (length > (t = pool.size() - addPos))
        {
                xorbuf(pool+addPos, inString, t);
                inString += t;
                length -= t;
                Stir();
        }

        if (length)
        {
                xorbuf(pool+addPos, inString, length);
                addPos += length;
                getPos = pool.size(); // Force stir on get
        }

        return 0;
}

size_t RandomPool::TransferTo2(BufferedTransformation &target, lword &transferBytes, const std::string &channel, bool blocking)
{
        if (!blocking)
                throw NotImplemented("RandomPool: nonblocking transfer is not implemented by this object");

        lword size = transferBytes;

        while (size > 0)
        {
                if (getPos == pool.size())
                        Stir();
                size_t t = UnsignedMin(pool.size() - getPos, size);
                target.ChannelPut(channel, pool+getPos, t);
                size -= t;
                getPos += t;
        }

        return 0;
}

byte RandomPool::GenerateByte()
{
        if (getPos == pool.size())
                Stir();

        return pool[getPos++];
}

void RandomPool::GenerateBlock(byte *outString, size_t size)
{
        ArraySink sink(outString, size);
        TransferTo(sink, size);
}

NAMESPACE_END

#endif

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