File: rc2.cpp

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// rc2.cpp - written and placed in the public domain by Wei Dai

#include "pch.h"
#include "rc2.h"
#include "misc.h"
#include "argnames.h"

NAMESPACE_BEGIN(CryptoPP)

void RC2::Base::UncheckedSetKey(const byte *key, unsigned int keyLen, const NameValuePairs &params)
{
	AssertValidKeyLength(keyLen);

	int effectiveLen = params.GetIntValueWithDefault(Name::EffectiveKeyLength(), DEFAULT_EFFECTIVE_KEYLENGTH);
	if (effectiveLen > MAX_EFFECTIVE_KEYLENGTH)
		throw InvalidArgument("RC2: effective key length parameter exceeds maximum");

	static const unsigned char PITABLE[256] = {
		217,120,249,196, 25,221,181,237, 40,233,253,121, 74,160,216,157,
		198,126, 55,131, 43,118, 83,142, 98, 76,100,136, 68,139,251,162,
		 23,154, 89,245,135,179, 79, 19, 97, 69,109,141,  9,129,125, 50,
		189,143, 64,235,134,183,123, 11,240,149, 33, 34, 92,107, 78,130,
		 84,214,101,147,206, 96,178, 28,115, 86,192, 20,167,140,241,220,
		 18,117,202, 31, 59,190,228,209, 66, 61,212, 48,163, 60,182, 38,
		111,191, 14,218, 70,105,  7, 87, 39,242, 29,155,188,148, 67,  3,
		248, 17,199,246,144,239, 62,231,  6,195,213, 47,200,102, 30,215,
		  8,232,234,222,128, 82,238,247,132,170,114,172, 53, 77,106, 42,
		150, 26,210,113, 90, 21, 73,116, 75,159,208, 94,  4, 24,164,236,
		194,224, 65,110, 15, 81,203,204, 36,145,175, 80,161,244,112, 57,
		153,124, 58,133, 35,184,180,122,252,  2, 54, 91, 37, 85,151, 49,
		 45, 93,250,152,227,138,146,174,  5,223, 41, 16,103,108,186,201,
		211,  0,230,207,225,158,168, 44, 99, 22,  1, 63, 88,226,137,169,
		 13, 56, 52, 27,171, 51,255,176,187, 72, 12, 95,185,177,205, 46,
		197,243,219, 71,229,165,156,119, 10,166, 32,104,254,127,193,173};

	SecByteBlock L(128);
	memcpy(L, key, keyLen);

	int i;
	for (i=keyLen; i<128; i++)
		L[i] = PITABLE[(L[i-1] + L[i-keyLen]) & 255];

	unsigned int T8 = (effectiveLen+7) / 8;
	byte TM = byte((int)255 >> ((8-(effectiveLen%8))%8));
	L[128-T8] = PITABLE[L[128-T8] & TM];

	for (i=127-T8; i>=0; i--)
		L[i] = PITABLE[L[i+1] ^ L[i+T8]];

	for (i=0; i<64; i++)
		K[i] = L[2*i] + (L[2*i+1] << 8);
}

typedef BlockGetAndPut<word16, LittleEndian> Block;

void RC2::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
	word16 R0, R1, R2, R3;
	Block::Get(inBlock)(R0)(R1)(R2)(R3);

	for (int i = 0; i < 16; i++)
	{
		R0 += (R1 & ~R3) + (R2 & R3) + K[4*i+0];
		R0 = rotlFixed(R0, 1);

		R1 += (R2 & ~R0) + (R3 & R0) + K[4*i+1];
		R1 = rotlFixed(R1, 2);

		R2 += (R3 & ~R1) + (R0 & R1) + K[4*i+2];
		R2 = rotlFixed(R2, 3);

		R3 += (R0 & ~R2) + (R1 & R2) + K[4*i+3];
		R3 = rotlFixed(R3, 5);

		if (i == 4 || i == 10)
		{
			R0 = word16(R0 + K[R3 & 63]);
			R1 = word16(R1 + K[R0 & 63]);
			R2 = word16(R2 + K[R1 & 63]);
			R3 = word16(R3 + K[R2 & 63]);
		}
	}

	Block::Put(xorBlock, outBlock)(R0)(R1)(R2)(R3);
}

void RC2::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
	word16 R0, R1, R2, R3;
	Block::Get(inBlock)(R0)(R1)(R2)(R3);

	for (int i = 15; i >= 0; i--)
	{
		if (i == 4 || i == 10)
		{
			R3 = word16(R3 - K[R2 & 63]);
			R2 = word16(R2 - K[R1 & 63]);
			R1 = word16(R1 - K[R0 & 63]);
			R0 = word16(R0 - K[R3 & 63]);
		}

		R3 = rotrFixed(R3, 5);
		R3 = word16(R3 - ((R0 & ~R2) + (R1 & R2) + K[4*i+3]));

		R2 = rotrFixed(R2, 3);
		R2 = word16(R2 - ((R3 & ~R1) + (R0 & R1) + K[4*i+2]));

		R1 = rotrFixed(R1, 2);
		R1 = word16(R1 - ((R2 & ~R0) + (R3 & R0) + K[4*i+1]));

		R0 = rotrFixed(R0, 1);
		R0 = word16(R0 - ((R1 & ~R3) + (R2 & R3) + K[4*i+0]));
	}

	Block::Put(xorBlock, outBlock)(R0)(R1)(R2)(R3);
}

NAMESPACE_END