A. C语言编程：编写一个函数base64加密
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
constchar*chlist="+/";
intencode_string(char*str,unsignedintlength,char*stat){
chars[103];
inti,j;
unsignedtemp;
if(length<=0)return1;
if(length>100)return2;
str[length]=' ';
strcpy(s,str);
while(strlen(s)%3)strcat(s,"=");
for(i=0,j=0;s[i];i+=3,j+=4){
temp=s[i];
temp=(temp<<8)+s[i+1];
temp=(temp<<8)+s[i+2];
stat[j+3]=chlist[temp&0X3F];
temp>>=6;
stat[j+2]=chlist[temp&0X3F];
temp>>=6;
stat[j+1]=chlist[temp&0X3F];
temp>>=6;
stat[j+0]=chlist[temp&0X3F];
}
stat[j]=' ';
return0;
}
intIndex(charch){
inti;
for(i=0;chlist[i];++i){
if(chlist[i]==ch)
returni;
}
return-1;
}
voiddecode_string(char*s,char*t){
unsignedtemp;
inti,j,k,len=strlen(s);
if(len%4){
printf("无效数据。 ");
exit(2);
}
for(i=0,j=0;i<=len;i+=4,j+=3){
temp=0;
for(k=0;k<4;++k)
temp=(temp<<6)+Index(s[i+k]);
for(k=2;k>=0;--k){
t[j+k]=temp&0XFF;
temp>>=8;
}
}
t[j+k]=' ';
}
intmain(){
chars[100]="1a2a3s4dff5fj6u7M8B9P0O1U2";
chart[150],u[100];
printf("s=%s ",s);
encode_string(s,strlen(s),t);
printf("t=%s ",t);
decode_string(t,u);
printf("u=%s ",u);
return0;
}
B. c语言实现密码加密
unsignedchar*encrypt(unsignedchar*psw,intenc){
intsum=0,i;
if(enc){
for(i=0;i<6;i++){
psw[i]-=15;
sum+=psw[i];
}
psw[6]=(unsignedchar)sum;
psw[7]=0;
}
else{
for(i=0;i<6;i++){
sum+=psw[i];
psw[i]+=15;
}
if((unsignedchar)sum!=psw[6]){
printf("Badpassword
");
psw[0]=0;
returnpsw;
}
else{
psw[6]=0;
}
}
for(i=0;i<3;i++){
unsignedchart=psw[i];
psw[i]=psw[5-i];
psw[5-i]=t;
}
returnpsw;
}
intmain()
{
unsignedcharpsw[128];
scanf("%s",psw);
printf("encodeto:%s
",encrypt(psw,1));
printf("decodeto:%s
",encrypt(psw,0));
return0;
}