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

#include "pch.h"
#include "rc2.h"

NAMESPACE_BEGIN(CryptoPP)

RC2Base::RC2Base(const byte *key, unsigned int keyLen, unsigned int effectiveLen)
	: K(64)
{
	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};

	assert(keyLen > 0 && keyLen <= 128);
	assert(effectiveLen <= 1024);

	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 = 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);
}

void RC2Encryption::ProcessBlock(const byte *in, byte *out) const
{
	word16 R0 = (in[1] << 8) + in[0];
	word16 R1 = (in[3] << 8) + in[2];
	word16 R2 = (in[5] << 8) + in[4];
	word16 R3 = (in[7] << 8) + in[6];

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

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

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

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

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

	out[0] = (byte)R0;
	out[1] = (byte)(R0 >> 8);
	out[2] = (byte)R1;
	out[3] = (byte)(R1 >> 8);
	out[4] = (byte)R2;
	out[5] = (byte)(R2 >> 8);
	out[6] = (byte)R3;
	out[7] = (byte)(R3 >> 8);
}

void RC2Decryption::ProcessBlock(const byte *in, byte *out) const
{
	word16 R0 = (in[1] << 8) + in[0];
	word16 R1 = (in[3] << 8) + in[2];
	word16 R2 = (in[5] << 8) + in[4];
	word16 R3 = (in[7] << 8) + in[6];

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

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

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

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

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

	out[0] = (byte)R0;
	out[1] = (byte)(R0 >> 8);
	out[2] = (byte)R1;
	out[3] = (byte)(R1 >> 8);
	out[4] = (byte)R2;
	out[5] = (byte)(R2 >> 8);
	out[6] = (byte)R3;
	out[7] = (byte)(R3 >> 8);
}

NAMESPACE_END