int sum = 0, i
if (enc) {
for (i = 0 i < 6 i++) {
psw[i] -= 15
sum += psw[i]
}
psw[6] = (unsigned char) sum
psw[7] = 0
}
else {
for (i = 0 i < 6 i++) {
sum += psw[i]
psw[i] += 15
}
if ((unsigned char)sum != psw[6]) {
printf("Bad password\n")
psw[0] = 0
return psw
}
else {
psw[6] = 0
}
}
for (i = 0 i < 3i++) {
unsigned char t = psw[i]
psw[i] = psw[5-i]
psw[5-i] = t
}
return psw
}
int main()
{
unsigned char psw[128]
scanf("%s", psw)
printf("encode to:%s\n", encrypt(psw, 1))
printf("decode to:%s\n", encrypt(psw, 0))
return 0
}
c语言文件加密和解密方法如下：
1、首先打开VC++6.0；
2、选择文件，新建；
3、选择C++ source file 新建一个空白文档；
4、声明头文件
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
首先写个加密函数，算法就是简介里说的
void EncryptFile(FILE *sfp,FILE *dfp,char pwd){
char ch
if(sfp==0||dfp==0)
{
printf("ERROR!\n")
return
}
while((ch=fgetc(sfp))!=EOF)
{
if((ch>='a')&&(ch<='z'))
{
ch=(ch-'a'+1)%26+'a'
ch=ch^pwd
}
if((ch>='A')&&(ch<='Z'))
{
ch=(ch-'A'+1)%26+'A'
ch=ch^pwd
}
fputc(ch,dfp)
}
}
写解密子函数：与加密的过程相反
void DecryptFile(FILE *sfp,FILE *dfp,char pwd){
char ch
while((ch=fgetc(sfp))!=EOF)
{
if((ch>='a')&&(ch<='z'))
{
ch=ch^pwd
ch=(ch-'a'+25)%26+'a'
}
if((ch>='A')&&(ch<='Z'))
{
ch=ch^pwd
ch=(ch-'A'+25)%26+'A'
}
fputc(ch,dfp)
}
}
输出函数，输出文件内容
void OutputFile(FILE *fp)
{
char ch
while((ch=fgetc(fp))!=EOF)
putchar(ch)
}
主函数，主要调用这几个函数
int main()
{
/*用户输入的要加密的文件名*/
char sfilename[20]
/*用户输入加密后保存的文件名*/
char dfilename[20]
/*用来保存密码字符*/
char pwd
FILE *sfp,*dfp
printf("\nPlease input filename to be encrypted:\n")
/*得到要加密的文件名*/
gets(sfilename)
/*得到加密后你要的文件名*/
printf("input filename to save the encrypted file:\n")
gets(dfilename)
/*得到加密字符*/
printf("Please input your Password:\n")
//scanf("%c",&pwd)
pwd=getch()
/*屏幕以*来表示输入的加密字符*/
printf("*\n")
/*以只读方式打开要加密的文件*/
if((sfp=fopen(sfilename,"r"))==0)
{
printf("Can't open the file :%s\n",sfilename)
exit(0)
}
/*输出要加密的文件*/
printf("\nThe the text of file to be encrypted is:\n")
OutputFile(sfp)
/*建立加密后的文件*/
if((dfp=fopen(dfilename,"w+"))==0)
{
printf("Can't open or create the file :%s\n",dfilename)
//exit(0)
}
/*文件加密*/
fseek(sfp,0L,SEEK_SET)
EncryptFile(sfp,dfp,pwd)
printf("\n\nEncrypted the file successfully!\n")
/*输出加密后的文件*/
printf("\nAfter encrypting the text of file is:\n")
fseek(dfp,0L,SEEK_SET)
OutputFile(dfp)
fclose(sfp)
fclose(dfp)
getch()
return 0
}
