// RandomGenerator.cpp: implementation of the CRandomGenerator class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "RSAUtil.h"
#include "RandomGenerator.h"
#include "BestMDHash.h"

#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

CRandomGenerator::CRandomGenerator()
{
	srand(time(NULL));
	m_nUpdateCounter = 0;
}

CRandomGenerator::~CRandomGenerator()
{
	SaveSeedIntoFile();
}

BOOL CRandomGenerator::
LoadSeedFromFile(const char* szFileName)
{
	m_strFileName = szFileName;

	FILE* fp = fopen(m_strFileName, "rb");
	if (NULL == fp)
	{
		return false;
	}

	fread(m_bySeed, 1, sizeof(m_bySeed), fp);

	fclose(fp);

	m_nUpdateCounter = 100;

	return true;
}

BOOL CRandomGenerator::
SaveSeedIntoFile()
{
	FILE* fp;

	fp = fopen(m_strFileName, "wb");
	if (NULL == fp)
	{
		return false;
	}

	fwrite(m_bySeed, 1, sizeof(m_bySeed), fp);
	
	fclose(fp);
	
	return true;
}

void CRandomGenerator::
Update(int n)
{
	BYTE			by16[16];
	
	GetMDHash(&n, sizeof(n), by16);
	n ^= rand();
	n %= sizeof(m_bySeed);
	for (int i = n; i < n + 16; i++)
	{
		m_bySeed[i % sizeof(m_bySeed)] ^= by16[i];
	}
	m_nUpdateCounter++;
	if (0 == (m_nUpdateCounter % 1024))
	{
		SaveSeedIntoFile();
	}
	for (i = 0; i < sizeof(m_bySeed); i++)
	{
		m_bySeed[i] ^= rand() % 0xff;
	}
	return;
}


void CRandomGenerator::
_RandomGetBytesEntropy(unsigned char* buf, unsigned l, unsigned effective)
{
	for (unsigned i = 0; i < l; i++)
	{
		buf[i] = m_bySeed[rand() % sizeof(m_bySeed)];
	}
}

/*
* Generate a random bignum of the specified length, with the given
* high and low 8 bits. "High" is merged into the high 8 bits of the
* number.  For example, set it to 0x80 to ensure that the number is
* exactly "bits" bits long (i.e. 2^(bits-1) <= bn < 2^bits).
* "Low" is merged into the low 8 bits.  For example, set it to
* 1 to ensure that you generate an odd number.
*/
int CRandomGenerator::
GenRand(CBigNumber *bn, unsigned bits, BYTE high, BYTE low, unsigned effective)
{
	unsigned char buf[64];
	unsigned bytes;
	unsigned l;
	int err;
	
	bnSetQ(bn, 0);
	
	/* Get high random bits */
	bytes = (bits+7) / 8;
	l = bytes < sizeof(buf) ? bytes : sizeof(buf);
	_RandomGetBytesEntropy(buf, l, effective);
	
	/* Mask off excess high bits */
	buf[0] &= 255 >> (-(int)bits & 7);
	/* Merge in specified high bits */
	buf[0] |= high >> (-(int)bits & 7);
	if (bits & 7)
		buf[1] |= high << (bits & 7);
	
	for (;;) {
		bytes -= l;
		if (!bytes)	/* Last word - merge in low bits */
			buf[l-1] |= low;
		err = bnInsertBigBytes(bn, buf, bytes, l);
		if (!bytes || err < 0)
			break;
		l = bytes < sizeof(buf) ? bytes : sizeof(buf);
		_RandomGetBytesEntropy(buf, l, 0);
	}
	
	/* Burn and return */
	return err;
}