rc4.c

实现RC4加解密方法

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <fcntl.h>      /* Needed only for _O_RDWR definition */
#include <io.h>

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


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

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

void main(void)
{
	UINT8 length,i;
	UINT8 buff[256];
	FILE *fin,*fout,*fp;
	int finno,foutno,fno;//file handle
	//unsigned int count = 0;//读取的字节数
	long filelen=0,count = 0;

	
	memset(inputdata,0,sizeof(inputdata));
	memset(outputdata,0,sizeof(outputdata));
	memset(mainkey,0,sizeof(mainkey));
	//产生16字节的随机数
	srand((UINT16)time(NULL));
	for(i=0;i<16;i++)  mainkey[i] = (UINT8)rand();

	
	fin = fopen("tt.txt","rb");
	fout = fopen("cipher.txt","wb");
	fp = fopen("plain.txt","wb");
	if( (fin == NULL) || (fout == NULL) || (fp == NULL) )
	{
		printf("file can't be opened\n");
		exit(-1);
	}

	finno = _fileno(fin);//get the file handle 
	foutno = _fileno(fout);
	fno = _fileno(fp);
	filelen = _filelength(finno);//get the length of the file


	memset(buff,0,sizeof(buff));
	while( filelen>0 )
	{
		count = read(finno,buff,sizeof(buff));
		printf("%s \n",buff);
		P_RC4(mainkey,buff,outputdata,count);			//加密
		write(foutno,outputdata,count);
		filelen = filelen - count;
		memset(buff,0,sizeof(buff));

	//	printf("%s \n",outputdata);

	}
	fclose(fout);
	fout = fopen("cipher.txt","rb");
 //cipher
	//rewind(fout);
	foutno = _fileno(fout);
	filelen = _filelength(foutno);//get the length of the file
	count = 0;
	memset(buff,0,sizeof(buff));
	while( filelen>0 )
	{
		count = read(foutno,buff,sizeof(buff));
		printf("%s \n",buff);
		P_RC4(mainkey,buff,outputdata,count);			//加密
		write(fno,outputdata,count);
		filelen = filelen - count;
		memset(buff,0,sizeof(buff));

	//	printf("%s \n",outputdata);

	}

	fclose(fin);
	fclose(fout);
	fclose(fp);
}

void P_RC4(UINT8 * pkey, UINT8 * pin, UINT8 * pout, long 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];
	}
}