rc4.c

uC/OS2系统下的rc4加密源码。开发环境：ads1.2

#include "config.h"

#define RC4_KEYSTATE_NUM	32		//默认：256

typedef struct rc4_key
{      
	uint8 state[RC4_KEYSTATE_NUM];       
	uint8 x;        
	uint8 y;
} rc4_key;


void prepareKey(const uint8 *keygen, uint32 keyDataLen, rc4_key *key)
{
	int i;
	uint8 *keyData;
	uint8 keyDataSeed[RC4_KEYSTATE_NUM];			

	uint8 swapByte;
	uint8 index1;
	uint8 index2;
	uint8* state;
	short counter;

	keyData = (uint8 *)(keygen);

	if ( keyDataLen > 512 )
		keyDataLen = 512;
	keyDataLen = (int)keyDataLen / 2;

	for (i=0;i<keyDataLen;i++)
	{
		keyDataSeed[i] = (keyData[i*2] + keyData[i*2+1])%RC4_KEYSTATE_NUM;
	}

	state = &key->state[0];
	for(counter = 0; counter < RC4_KEYSTATE_NUM; counter++)
		state[counter] = (uint8)counter;
	key->x = 0;	key->y = 0;
	index1 = 0;	index2 = 0;


	for(counter = 0; counter < RC4_KEYSTATE_NUM; counter++)
	{
		index2 = (keyDataSeed[index1] + state[counter] + index2) % RC4_KEYSTATE_NUM;
		swapByte = state[counter]; 
		state[counter] = state[index2];
		state[index2] = swapByte;
		index1 = (index1 + 1) % keyDataLen;
	}

}

void RC4(const uint8 *keygen, uint32 keyDataLen, void *dataBuffer, uint16 bufferLen)
{
	uint8 x;
	uint8 y;
	uint16 counter;
	uint8 swapByte;
	uint8* state;
	uint8 xorIndex;			
	uint8 *buffer_ptr;
	rc4_key key;

	prepareKey(keygen, keyDataLen, &key);

	buffer_ptr = (uint8 *)(dataBuffer);

	x = key.x;
	y = key.y;
	state = &key.state[0];
	for(counter = 0; counter < bufferLen; counter++)
	{
		x = (x + 1) % RC4_KEYSTATE_NUM;
		y = (state[x] + y) % RC4_KEYSTATE_NUM;
		swapByte = state[x]; 
		state[x] = state[y];
		state[y] = swapByte;

		xorIndex = (state[x] + state[y]) % RC4_KEYSTATE_NUM;
		buffer_ptr[counter] ^= state[xorIndex];
	}
}