crypt.c

栅格加密法,IDE vc6,方法比较简单,适合初学者理解

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

char sourse[20],cryptograph[20],temp;
int len,i,j,k,n,p[10],len2;
void incrypt(char s[20])
{
	len=strlen(s);
	n=3;  //栅格数
	for(i=0;i<=len-1;i++) 
	{
		s[i]+=7;
		cryptograph[i]=s[i];
	}
	k=0;
	for(i=1;i<=n;i++)//栅格加密
	{
		j=i-1;
		while(j<=len-1)
		{
			cryptograph[k]=s[j];
			j+=n;
			k++;
		}
	}
	return 0;
}
void decrypt(char s[20])
{
	len=strlen(s);
	n=3;//栅格数
	len2=len;
	i=1;
	while (len2>=0)  //计算每个栅格长度
	{
		if (len2 % n !=0) 
		{
			p[i]=len/n+1;
			len2-=(n+1);
			i++;
		}
		else
		{
			p[i]=len/n;
			len2-=n;
			i++;
		}
	}
	p[i]=len/n;
	p[0]=len/n;
	for(i=0;i<=len-1;i++) 
	{
		s[i]-=7;
		sourse[i]=s[i];
	}
	k=0;
	for(i=1;i<=(len/n)+1;i++) //栅格解密
	{
		for(j=i-1;j<=len-1;j+=p[k % n])
		{
			sourse[k]=s[j];
			k++;
			if (k>len-1) return 0; //实在没辙了..
		}
	}
	return 0;
}
main()
{
	scanf("%s",&sourse);
	incrypt(sourse);
	printf("%s\n",cryptograph);
	decrypt(cryptograph);
	printf("%s\n",sourse);
	scanf("%s",&sourse);
}