Question

我的cocos2d游戏使用CCCrypt（）加密保存数据。我使用mac地址作为加密密钥。在IOS5中加密的保存文件无法使用IOS6中的相同mac地址进行解密。这意味着更新游戏的用户将丢失所有数据！

有没有办法解密旧文件？

这是代码：

@implementation NSData (AESAdditions)
- (NSData*)AES256EncryptWithKey:(NSString*)key {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256 + 1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)

    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [self length];

    //See the doc: For block ciphers, the output size will always be less than or
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize           = dataLength + kCCBlockSizeAES128;
    void* buffer                = malloc(bufferSize);

    size_t numBytesEncrypted    = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesEncrypted);

    if (cryptStatus == kCCSuccess)
    {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
    }

    free(buffer); //free the buffer;
    return nil;
}
- (NSData *)AES256DecryptWithKey:(NSString *)key {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char keyPtr[kCCKeySizeAES256+1]; // room for terminator (unused)
    bzero(keyPtr, sizeof(keyPtr)); // fill with zeroes (for padding)

    // fetch key data
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [self length];

    //See the doc: For block ciphers, the output size will always be less than or
    //equal to the input size plus the size of one block.
    //That's why we need to add the size of one block here
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);

    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
                                          keyPtr, kCCKeySizeAES256,
                                          NULL /* initialization vector (optional) */,
                                          [self bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesDecrypted);

    if (cryptStatus == kCCSuccess) {
        //the returned NSData takes ownership of the buffer and will free it on deallocation
        return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
    }

    free(buffer); //free the buffer;
    return nil;
}
@end

Answer 1

您需要详细说明如何实施加密，尤其是您使用的选项。

根据我的经验，iOS 6解密失败的最常见原因是他们更改/修复的CTR错误。在iOS 5中，选项kCCModeOptionCTR_LE是谎言。它实际上是用kCCModeOptionCTR_BE加密的。在iOS 6中，他们修复此问题，如果您尝试使用kCCModeOptionCTR_LE，则会收到“未实现”错误。但是CCCrypt（）通常不使用CTR模式，所以我不知道这是否适用。

Answer 2

好的，我找到了解决方案。

这里的关键点：

我向NSData添加了两个方法，用基于代码的IOS5 lib加密和解密。

@implementation NSData (AESAdditions)
-(NSData*)AES256EncryptWithKey:(NSString*)key;
-(NSData *)AES256DecryptWithKey:(NSString *)key

现在在IOS6 lib中，NSData可能会被更改，因此两种方法的工作方式不同，它无法解密IOS5中的文件加密。

在我的基于IOS6的代码中，我在课堂上编写了方法。像这样：

- (NSData*)AES256EncryptWithKey:(NSString*)key data:(NSData *)data;
- (NSData *)AES256DecryptWithKey:(NSString *)key data:(NSData *)data;

代码与IOS5中的代码完全相同。

使用ios5加密的CCCrypt无法使用ios6进行解密

2 个答案: