一般的解密方法（步骤）：
一、复制一份文件，例如a.php；
二、把a.php文件里面的第一个eval修改为exit；
三、在控制台运行a.php，复制输出的内容，替换eval那一行，例如:
c:\>php a.php >1
c:\>notepad 1
这样打开一个记事本，然后全选、复制、关闭窗口，然后在a.php里面选择刚才修改的exit的那个语句，从eval开始到结束，然后粘贴，保存，关闭。
四、如果文件里面还有eval，跳转到第二步。
过程中注意，里面的_FILE_要修改为原来的文件名字，并且记住增加了多少字节，在fgets的时候要适当调整。
//下面程序由520huiqin编写，已在VC++ 6.0下编译通过#include <iostream.h>
#include <math.h>
#include <stdio.h>
typedef int Elemtype
Elemtype p,q,e
Elemtype fn
Elemtype m,c
int flag = 0
typedef void (*Msghandler) (void)
struct MsgMap {
char ch
Msghandler handler
}
/* 公钥 */
struct PU {
Elemtype e
Elemtype n
} pu
/* 私钥 */
struct PR {
Elemtype d
Elemtype n
} pr
/* 判定一个数是否为素数 */
bool test_prime(Elemtype m) {
if (m <= 1) {
return false
}
else if (m == 2) {
return true
}
else {
for(int i=2i<=sqrt(m)i++) {
if((m % i) == 0) {
return false
break
}
}
return true
}
}
/* 将十进制数据转化为二进制数组 */
void switch_to_bit(Elemtype b, Elemtype bin[32]) {
int n = 0
while( b >0) {
bin[n] = b % 2
n++
b /= 2
}
}
/* 候选菜单，主界面 */
void Init() {
cout<<"*********************************************"<<endl
cout<<"*** Welcome to use RSA encoder ***"<<endl
cout<<"*** a.about ***"<<endl
cout<<"*** e.encrypt ***"<<endl
cout<<"*** d.decrypt ***"<<endl
cout<<"*** s.setkey***"<<endl
cout<<"*** q.quit ***"<<endl
cout<<"**********************************by*Terry***"<<endl
cout<<"press a key:"<<endl
}
/* 将两个数排序，大的在前面*/
void order(Elemtype &in1, Elemtype &in2) {
Elemtype a = ( in1 >in2 ? in1 : in2)
Elemtype b = ( in1 <in2 ? in1 : in2)
in1 = a
in2 = b
}
/* 求最大公约数 */
Elemtype gcd(Elemtype a, Elemtype b) {
order(a,b)
int r
if(b == 0) {
return a
}
else {
while(true) {
r = a % b
a = b
b = r
if (b == 0) {
return a
break
}
}
}
}
/* 用扩展的欧几里得算法求乘法逆元 */
Elemtype extend_euclid(Elemtype m, Elemtype bin) {
order(m,bin)
Elemtype a[3],b[3],t[3]
a[0] = 1, a[1] = 0, a[2] = m
b[0] = 0, b[1] = 1, b[2] = bin
if (b[2] == 0) {
return a[2] = gcd(m, bin)
}
if (b[2] ==1) {
return b[2] = gcd(m, bin)
}
while(true) {
if (b[2] ==1) {
return b[1]
break
}
int q = a[2] / b[2]
for(int i=0i<3i++) {
t[i] = a[i] - q * b[i]
a[i] = b[i]
b[i] = t[i]
}
}
}
/* 快速模幂算法 */
Elemtype modular_multiplication(Elemtype a, Elemtype b, Elemtype n) {
Elemtype f = 1
Elemtype bin[32]
switch_to_bit(b,bin)
for(int i=31i>=0i--) {
f = (f * f) % n
if(bin[i] == 1) {
f = (f * a) % n
}
}
return f
}
/* 产生密钥 */
void produce_key() {
cout<<"input two primes p and q:"
cin>>p>>q
while (!(test_prime(p)&&test_prime(q))){
cout<<"wrong input,please make sure two number are both primes!"<<endl
cout<<"input two primes p and q:"
cin>>p>>q
}
pr.n = p * q
pu.n = p * q
fn = (p - 1) * (q - 1)
cout<<"fn = "<<fn<<endl
cout<<"input e :"
cin>>e
while((gcd(fn,e)!=1)) {
cout<<"e is error,try again!"
cout<<"input e :"
cin>>e
}
pr.d = (extend_euclid(fn,e) + fn) % fn
pu.e = e
flag = 1
cout<<"PR.d: "<<pr.d<<" PR.n: "<<pr.n<<endl
cout<<"PU.e: "<<pu.e<<" PU.n: "<<pu.n<<endl
}
/* 加密 */
void encrypt() {
if(flag == 0) {
cout<<"setkey first:"<<endl
produce_key()
}
cout<<"input m:"
cin>>m
c = modular_multiplication(m,pu.e,pu.n)
cout<<"c is:"<<c<<endl
}
/* 解密 */
void decrypt() {
if(flag == 0) {
cout<<"setkey first:"<<endl
produce_key()
}
cout<<"input c:"
cin>>c
m = modular_multiplication(c,pr.d,pr.n)
cout<<"m is:"<<m<<endl
}
/* 版权信息 */
void about() {
cout<<"*********************************************"<<endl
cout<<"*** by Terry***"<<endl
cout<<"*** copyright 2010,All rights reserved by ***"<<endl
cout<<"*** Terry,technology supported by weizuo !***"<<endl
cout<<"*** If you have any question, please mail ***"<<endl
cout<<"*** to 18679376@qq.com !***"<<endl
cout<<"*** Computer of science and engineering ***"<<endl
cout<<"*** XiDian University2010-4-29***"<<endl
cout<<"*********************************************"<<endl
cout<<endl<<endl
Init()
}
/* 消息映射 */
MsgMap Messagemap[] = {
{'a',about},
{'s',produce_key},
{'d',decrypt},
{'e',encrypt},
{'q',NULL}
}
/* 主函数，提供循环 */
void main() {
Init()
char d
while((d = getchar())!='q') {
int i = 0
while(Messagemap[i].ch) {
if(Messagemap[i].ch == d) {
Messagemap[i].handler()
break
}
i++
}
}
}
//欢迎分享，盗窃可耻
C语言设计一个简单的加密解密程序如下：加密程序代码：
#include<stdio.h>
main()
{
char c,filename[20]
FILE *fp1,*fp2
printf("请输入待加密的文件名:\n")
scanf("%s",filename)
fp1=fopen(filename,"r")
fp2=fopen("miwen.txt","w")
do
{
c=fgetc(fp1)
if(c>=32&&c<=126)
{
c=c-32
c=126-c
}
if(c!=-1)
fprintf(fp2,"%c",c)
}
while(c!=-1)
}
解密程序代码：
#include<stdio.h>
#include<string.h>
main()
{
char c,filename[20]
char yanzhengma[20]
FILE *fp1,*fp2
printf("请输入待解密文件名:\n")
scanf("%s",filename)
printf("请输入验证码:\n")
scanf("%s",yanzhengma)
if(strcmp(yanzhengma,"shan")==0)
{
fp1=fopen(filename,"r")
fp2=fopen("yuanwen.txt","w")
do
{
c=fgetc(fp1)
if(c>=32&&c<=126)
{
c=126-c
c=32+c
}
if(c!=-1)
fprintf(fp2,"%c",c)
}
while(c!=-1)
}
else
{
printf("验证码错误！请重新输入:\n")
scanf("%s",filename)
}
}
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