decode.c

十六位的RSA加解密程序。程序中包括生成公钥和私钥的生成

#include "decode.h"

int main()
{
	FILE *pf1,*pf2,*pf3;
	unsigned long n,d;
	unsigned char PText[2],CText[3];

	pf1=fopen("SK.bin","r");		//取私钥
	fscanf(pf1,"%X-%X",&n,&d);
	fclose(pf1);

	pf2=fopen("Cipher.txt","rb");
	pf3=fopen("Plaint.txt","wb");

	CText[0]=0;
	CText[1]=0;
	CText[2]=0;
	while(fread(CText,1,2,pf2)!=0)
	{
		decode(CText,PText,n,d);	//解密一段密文
		CText[0]=0;
		CText[1]=0;
		CText[2]=0;
		fwrite(PText,1,1,pf3);
	}
	fclose(pf2);
	fclose(pf3);

	return 0;
}

void decode(unsigned char *cT,unsigned char *pT,unsigned long n,unsigned long d)
{
	unsigned long i;
	unsigned long p,c;
	c=(unsigned long)(cT[0]);
	c=c+(((unsigned long)(cT[1]))<<8);

	p=1;
	for (i=0;i<16;i++)		//快速幂模求法
	{
		if ((d&0x0001)!=0)
			p=(c*p)%n;
		c=(c*c)%n;
		d=d>>1;
	}

	pT[0]=(unsigned char)(p&0xff);

	return;
}