Cocos2d-x数据加密解密详解

C++的Base64算法实现

/*
 * base64.cpp
 *
 *  Created on: 30/04/2011
 *      Author: nicholas
 */
#include "base64.h"
#include <cctype>
//#include <cstdint>
#include <algorithm>
namespace base64
{
namespace
{
static const std::string BASE64_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
size_t encoded_size(size_t raw)
{
switch((raw*8)%6)
{
case 0:
return (raw*8)/6;
case 2:
return ((raw*8)/6) + 3;
case 4:
return ((raw*8)/6) + 2;
}
return raw;
}
size_t decoded_size(size_t unpadded)
{
return (unpadded*6)/8;
}
int base64_index(std::string::value_type c)
{
if(c >= 'A' && c <= 'Z')
return c-'A';
else if(c >= 'a' && c <= 'z')
return c-'a' + 26;
else if(c >= '0' && c <= '9')
return c-'0' + 52;
else if(c == '+')
return 62;
else if(c == '/')
return 63;
else
return -1;
}
}
encode_t::encode_t(std::string::size_type size)
 : state(zero),remainder(0)
{
encoded.reserve(encoded_size(size));
}
/*
State zero
8 bits input,zero remaining from last
6 bits consumed,2 remaining
=> two
State two
8 bits input,2 remaining from last
4 bits consumed,4 remaining
=> four
State four
8 bits input,4 remaining from last
2 bits consumed,6 remaining
6 bits input,6 remaining from last
6 bits consumed,0 remaining
=> zero
 */
void encode_t::operator() (std::string::value_type c)
{
unsigned char value(0);
switch(state)
{
case zero:
value = (c & 0xfc) >> 2;
remainder = c & 0x3;
encoded.push_back(BASE64_CHARS[value]);
state = two;
break;
case two:
value = (remainder << 4) | ((c & 0xf0) >> 4);
remainder = c & 0xf;
encoded.push_back(BASE64_CHARS[value]);
state = four;
break;
case four:
value = (remainder << 2) | ((c & 0xc0) >> 6);
remainder = c & 0x3f;
encoded.push_back(BASE64_CHARS[value]);
value = remainder;
encoded.push_back(BASE64_CHARS[value]);
state = zero;
break;
}
}
std::string encode_t::str()
{
unsigned char value(0);
switch(state)
{
case zero:
break;
case two:
value = remainder << 4;
encoded.push_back(BASE64_CHARS[value]);
encoded.push_back('=');
encoded.push_back('=');
state = zero;
break;
case four:
value = remainder << 2;
encoded.push_back(BASE64_CHARS[value]);
encoded.push_back('=');
state = zero;
break;
}
return encoded;
}
decode_t::decode_t(std::string::size_type size)
 : state(zero),remainder(0)
{
decoded.reserve(decoded_size(size));
}
/*
State zero
6 bits input,zero remaining
=> six
State six
6 bits input,6 remaining from last
write 1 byte,4 remaining
=> four
State four
6 bits input,4 remaining from last
write 1 byte,2 remaining
=> two
State two
6 bits input,2 remaining from last
write 1 byte,0 remaining
=> zero
 */
void decode_t::operator() (std::string::value_type c)
{
unsigned char value(0);
int index = base64_index(c);
if(index == -1)
return;
switch(state)
{
case zero:
remainder = index;
state = six;
break;
case six:
value = (remainder << 2) | ((index & 0x30) >> 4);
remainder = index & 0xf;
decoded.push_back(value);
state = four;
break;
case four:
value = (remainder << 4) | ((index & 0x3c) >> 2);
remainder = index & 0x3;
decoded.push_back(value);
state = two;
break;
case two:
value = (remainder << 6) | index;
decoded.push_back(value);
state = zero;
break;
}
}
std::string decode_t::str() const
{
return decoded;
}
std::string encode(const std::string& str)
{
return std::for_each(str.begin(),str.end(),encode_t(str.size())).str();
}
std::string decode(const std::string& str)
{
size_t unpadded_size = str.size();
if(str.size() > 0 && str[str.size()-1] == '=')
unpadded_size -= 1;
if(str.size() > 1 && str[str.size()-2] == '=')
unpadded_size -= 1;
return std::for_each(str.begin(),decode_t(unpadded_size)).str();
}
}

/*
 * base64.h
 *
 *  Created on: 30/04/2011
 *      Author: nicholas
 */
#ifndef BASE64_H_
#define BASE64_H_
#include <string>
namespace base64
{
class encode_t
{
private:
enum
{
zero = 0,two,four
} state;
unsigned int remainder;
std::string encoded;
public:
encode_t(std::string::size_type size);
void operator() (std::string::value_type c);
std::string str();
};
class decode_t
{
private:
enum
{
zero = 0,six,four,two
} state;
unsigned int remainder;
std::string decoded;
public:
decode_t(std::string::size_type size);
void operator() (std::string::value_type c);
std::string str() const;
};
/*
 * Encode the given string @str into its base64 representation
 */
std::string encode(const std::string& str);
/*
 * Decode the base64 encoded string @str
 */
std::string decode(const std::string& str);
}
#endif /* BASE64_H_ */

#include<iostream>
#include"base64.h"
using namespace std;
int main ()
{
    string str = "abcdefghijklmn.";
    string out = base64::encode(str);    
    cout<<"src:"<<str<<endl; 
    cout<<"encode: "<<out<<endl;
    cout<<"decode: "<<base64::decode(out)<<endl;
     
     
    str = "ä¸ć.";
    out = base64::encode(str);    
    cout<<endl<<"src:"<<str<<endl;
    cout<<"encode: "<< out <<endl;
    cout<<"decode: "<< base64::decode(out) <<endl;
     
    system("pause");
    return 1;    
}

Android平台下使用Base64算法加密解密数据

import com.example.base64.R;
import android.app.Activity;
import android.os.Bundle;
import android.util.Base64;
public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        String src = "abcdefjhijklmn.";
        // 加密数据
        String encode = Base64.encodeToString(src.getBytes(),Base64.DEFAULT);
        // 解密数据
        String decode = new String(Base64.decode(encode,Base64.DEFAULT));
        System.out.println("src：" + src);
        System.out.println("encode：" + encode);
        System.out.println("decode：" + decode);
    }
}

数据库数据项加密

Cocos2d-x中操作数据库的实现都封装在LocalStorage这个类中。使用的是sqlite3。

iOS、Win32平台的加密

1.base64.h和base64.cpp添加项目Classes目录下。

2.右键libExtensions项目，附加包含目录，把base64库所在目录添加到包含目录中，具体路径根据自己项目结构而定

3.修改localStorageSetItem方法，保存数据时加密数据，这里在win32平台下忽略加密操作是因为一般win32平台版本是用于内部测试的

void localStorageSetItem( const char *key,const char *value)  
{  
    assert( _initialized );  
   
    // 加密数据  
    #if (CC_TARGET_PLATFORM != CC_PLATFORM_WIN32)  
        //CCLOG("key=%s src=%s",key,value);         
        std::string encodeStr = base64::encode(value);  
        value = encodeStr.c_str();  
        //CCLOG("key=%s encode=%s",value);  
    #endif  
       
    int ok = sqlite3_bind_text(_stmt_update,1,-1,sqlITE_TRANSIENT);  
    ok |= sqlite3_bind_text(_stmt_update,2,value,sqlITE_TRANSIENT);  
   
    ok |= sqlite3_step(_stmt_update);  
       
    ok |= sqlite3_reset(_stmt_update);  
       
    if( ok != sqlITE_OK && ok != sqlITE_DONE)  
        printf("Error in localStorage.setItem()\n");  
}

4.修改localStorageGetItem方法，获取数据时解密数据

const char* localStorageGetItem( const char *key )  
{  
    assert( _initialized );  
   
    int ok = sqlite3_reset(_stmt_select);  
   
    ok |= sqlite3_bind_text(_stmt_select,sqlITE_TRANSIENT);  
    ok |= sqlite3_step(_stmt_select);  
    const unsigned char *ret = sqlite3_column_text(_stmt_select,0);  
       
   
    if( ok != sqlITE_OK && ok != sqlITE_DONE && ok != sqlITE_ROW)  
        printf("Error in localStorage.getItem()\n");  
   
    // 加密数据  
    #if (CC_TARGET_PLATFORM != CC_PLATFORM_WIN32)  
        //CCLOG("decode src=%s",ret);    
        if (ret)  
        {  
            std::string decodeStr = base64::decode((const char*)ret);                         
               
            char* c = new char;               
            strcpy_s(c,decodeStr.size() + 1,decodeStr.c_str());    
            //CCLOG("key=%s decode=%s",c);              
            return c;  
        }         
    #endif  
   
    return (const char*)ret;  
}

注意：c_str()方法返回的是string对象中保留的字符串指针，该指针的生命周期是跟随string对象的。也就是如果直接返回decodeStr.c_str()，返回的将是垃圾数据，因为decodeStr在函数结束后，已经被销毁了，指针所指向的是垃圾数据。

这种数据库加密方案存在以下几个问题：

1.如果别人知道我所使用的加密算法，然后通过程序计算出加密串，还是可以修改成功的。

2.数据库还是可以用相关工具打开，并查看数据表。

3.每次读写数据时，增加了加密解密的步骤，降低效率。

对于Cocos2d-x中数据库的加密有更好的解决办法，就是使用wxsqlite3，点击查看【集成wxSqlite3到Cocos2d-x】，这种数据库加密的实现是在初始化数据库的时候加密，运行时加载数据库时候调用相关api解密，加载完成后数据的读写效率和未加密时一样，相对比较高效。

Android平台的加密

从LocalStorage.cpp中使用的宏可以看出，这个实现在安卓平台下是无法使用的。

安卓平台下的实现在：cocos2d-x-2.1.5\extensions\LocalStorage目录下的LocalStorageAndroid.cpp中。

从localStrorageInit的实现可以看出，它是通过jni调用了java层中org/cocos2dx/lib/Cocos2dxLocalStorage的静态方法init。

在打包安卓版Cocos2d-x游戏时需要用到引擎的一个java库，在cocos2d-x-2.1.5\cocos2dx\platform\android\java目录下，Cocos2dxLocalStorage类就在这个库中。

修改这个类的setItem方法，在保存数据的时候加密

public static void setItem(String key,String value) {  
    try {  
        // 加密数据  
        value = Base64.encodeToString(value.getBytes(),Base64.DEFAULT);  
   
        String sql = "replace into " + TABLE_NAME  
                + "(key,value)values(?,?)";  
        mDatabase.execsql(sql,new Object[] { key,value });  
    } catch (Exception e) {  
        e.printStackTrace();  
    }  
}

修改这个类的getItem方法，在获取数据的时候解密

public static String getItem(String key) {  
    String ret = null;  
    try {  
        String sql = "select value from " + TABLE_NAME + " where key=?";  
        Cursor c = mDatabase.rawQuery(sql,new String[] { key });  
        while (c.moveToNext()) {  
            // only return the first value  
            if (ret != null) {  
                Log.e(TAG,"The key contains more than one value.");  
                break;  
            }  
            ret = c.getString(c.getColumnIndex("value"));  
        }  
        c.close();  
    } catch (Exception e) {  
        e.printStackTrace();  
    }  
       
    // 解密数据  
    if (ret != null) {  
        ret = new String(Base64.decode(ret,Base64.DEFAULT));  
    }  
       
    return ret == null ? "" : ret;  
}

来源网址：http://www.jb51.cc/article/p-ygjicaym-bea.html

Cocos2d-x数据加密解密详解

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