#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>

typedef unsigned char  UINT8;
typedef unsigned short UINT16;
typedef unsigned long  UINT32;

const UINT8 C_data[] =
{
	1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
};

UINT8 inputdata[256],outputdata[256];
UINT8 mainkey[16];

void P_RC4(UINT8 * pkey, UINT8 * pin, UINT8 * pout, UINT8 len);

void main(void)
{
	UINT8 length,i;
	
	memset(inputdata,0,sizeof(inputdata));
	memset(outputdata,0,sizeof(outputdata));
	memset(mainkey,0,sizeof(mainkey));
	length = sizeof(C_data);
	memcpy(inputdata,C_data,length);
	for(i=0;i<length;i++)  printf("%02x ",inputdata[i]);
	printf("\n");printf("\n");

	srand((UINT16)time(NULL));
	for(i=0;i<16;i++)  mainkey[i] = (UINT8)rand();		//產生16字節的隨機數
	
	P_RC4(mainkey,inputdata,outputdata,length);			//加密
	for(i=0;i<length;i++)  printf("%02x ",outputdata[i]);
	printf("\n");printf("\n");

	memset(inputdata,0,sizeof(inputdata));
	P_RC4(mainkey,outputdata,inputdata,length);			//解密
	for(i=0;i<length;i++)  printf("%02x ",inputdata[i]);
	printf("\n");printf("\n");
}

void P_RC4(UINT8 * pkey, UINT8 * pin, UINT8 * pout, UINT8 len)
{
	UINT8 S[256],K[256],temp;
	UINT32 i,j,t,x;
	
	j = 1;
	for(i=0;i<256;i++)
	{
		S[i] = (UINT8)i;
		if(j > 16) j = 1;
		K[i] = pkey[j-1];
		j++;
	}
	j = 0;
	for(i=0;i<256;i++)
	{
		j = (j + S[i] + K[i]) % 256;
		temp = S[i];
		S[i] = S[j];
		S[j] = temp;
	}
	i = j = 0;
	for(x=0;x<len;x++)
	{
		i = (i+1) % 256;
		j = (j + S[i]) % 256;
		temp = S[i];
		S[i] = S[j];
		S[j] = temp;
		t = (S[i] + (S[j] % 256)) % 256;
		pout[x] = pin[x] ^ S[t];
	}
}