rc6.cpp

一个DES,RSA,MD5,RC4等加密算法的源码

// rc6.cpp - written and placed in the public domain by Sean Woods
// based on Wei Dai's RC5 code.

#include "pch.h"
#include "rc6.h"

NAMESPACE_BEGIN(CryptoPP)

RC6Base::RC6Base(const byte *k, unsigned int keylen, unsigned int rounds)
	: r(rounds), sTable((2*r)+4)
{
	assert(keylen == KeyLength(keylen));

	static const RC6_WORD MAGIC_P = 0xb7e15163L;    // magic constant P for wordsize
	static const RC6_WORD MAGIC_Q = 0x9e3779b9L;    // magic constant Q for wordsize
	static const int U=sizeof(RC6_WORD);

	const unsigned int c=(keylen+U-1)/U;
	SecBlock<RC6_WORD> l(c);

	GetUserKeyLittleEndian(l.ptr, c, k, keylen);

	sTable[0] = MAGIC_P;
	for (unsigned j=1; j<sTable.size;j++)
		sTable[j] = sTable[j-1] + MAGIC_Q;

	RC6_WORD a=0, b=0;
	const unsigned n = 3*STDMAX(sTable.size,c);

	for (unsigned h=0; h < n; h++)
	{
		a = sTable[h % sTable.size] = rotlFixed((sTable[h % sTable.size] + a + b), 3);
		b = l[h % c] = rotlMod((l[h % c] + a + b), (a+b));
	}
}

void RC6Encryption::ProcessBlock(const byte *in, byte *out) const
{
	const RC6_WORD *sptr = sTable;
	RC6_WORD a, b, c, d, t, u;

	GetBlockLittleEndian(in, a, b, c, d);
	b += sptr[0];
	d += sptr[1];
	sptr += 2;

	for(unsigned i=0; i<r; i++)
	{
		t = rotlFixed(b*(2*b+1), 5);
		u = rotlFixed(d*(2*d+1), 5);
		a = rotlMod(a^t,u) + sptr[0];
		c = rotlMod(c^u,t) + sptr[1];
		t = a; a = b; b = c; c = d; d = t;
		sptr += 2;
	}

	a += sptr[0];
	c += sptr[1];

	PutBlockLittleEndian(out, a, b, c, d);
}

void RC6Decryption::ProcessBlock(const byte *in, byte *out) const
{
	const RC6_WORD *sptr = sTable+sTable.size;
	RC6_WORD a, b, c, d, t, u;

	GetBlockLittleEndian(in, a, b, c, d);

	sptr -= 2;
	c -= sptr[1];
	a -= sptr[0];

	for (unsigned i=0; i < r; i++)
	{
		sptr -= 2;
		t = a; a = d; d = c; c = b; b = t;
		u = rotlFixed(d*(2*d+1), 5);
		t = rotlFixed(b*(2*b+1), 5);
		c = rotrMod(c-sptr[1], t) ^ u;
		a = rotrMod(a-sptr[0], u) ^ t;
	}

	sptr -= 2;
	d -= sTable[1];
	b -= sTable[0];

	PutBlockLittleEndian(out, a, b, c, d);
}

NAMESPACE_END