文件加密算法研究示例

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
struct sysuser
{
    char username[20];
    char password[8];
};
void encrypt(char *pwd);
int main()
{
    FILE *fp;
    int i;
    struct sysuser su;
    if ((fp = fopen("*f12-2.txt", "w")) == NULL)
    {
        printf("File open error!\n");
        exit(0);
    }
    for (i = 1; i <= 5; i++)
    {
        printf("Enter %d th sysuser(name password):", i);
        scanf("%s%s", su.username, su.password);
        encrypt(su.password);
        fprintf(fp, "%s%s\n", su.username, su.password);
    }
    if (fclose(fp))
    {
        printf("Can not close the file!\n");
        exit(0);
    }
    return 0;
}
void encrypt(char *pwd)
{
    int i;
    for (i = 0; i < strlen(pwd); i++)
        pwd[i] = pwd[i] ^ 15;
}