使用Java对使用Objective-C进行AES加密的数据进行解密 [英] Decrypting data that was AES encrypted with Objective-C with Java

问题描述

我尝试解密最初用Java中的Objective-C加密的数据。

I try to decrypt data that was originally encrypted with Objective-C in Java.

还有其他问题，但他们真的很混乱，许多都没有解决，因此我会发布自己的。

There are other questions mentioning this but they are really cluttered and many of them aren't solved yet therefore I will post my own.

这是加密数据的代码：

  - (int) encryptWithKey: (NSString *) key
    {
    // 'key' should be 32 bytes for AES256, will be null-padded otherwise
    char * keyPtr[kCCKeySizeAES128+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];

    // encrypts in-place, since this is a mutable data object
    size_t numBytesEncrypted = 0;
    CCCryptorStatus result = CCCrypt( kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding, 
                                     keyPtr, kCCKeySizeAES128,
                                     NULL /* initialization vector (optional) */, 
                                     [self mutableBytes], [self length], /* input */
                                     [self mutableBytes], [self length]+32, /* output */
                                     &numBytesEncrypted );
    return numBytesEncrypted;
}

我执行此函数并将结果数据写入光盘，

I execute this function and write the resulting data to the disc with this code:

NSString* strTest = @"Hallo Welt!";
NSLog(@"strTest = %@", strTest);

NSMutableData *protectedData = [NSMutableData dataWithData:[strTest dataUsingEncoding:NSUTF8StringEncoding]];

int laenge = [protectedData encryptWithKey:@"keykeykeykeykeykeykeykey"];

NSData* dataOutput = [[NSData alloc] initWithBytes:[protectedData bytes] length:laenge];


[dataOutput writeToFile:@"/encryptedFileObjC" atomically:YES];

在Java中，我使用此代码尝试实现相同的行为：

In Java I use this code to try to achieve the same behavior:

Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
String keyString = "keykeykeykeykeykeykeykey";
byte[] keyBytes = keyString.getBytes("UTF-8");

cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(keyBytes, "AES"),
        new IvParameterSpec(new byte[16]));
byte[] resultBytes = cipher.doFinal("Hallo Welt!".getBytes("UTF8"));

FileOutputStream out =
        new FileOutputStream(new File("encryptedFileJava"));
out.write(resultBytes);
out.close();

如果我现在尝试解密通过Objective-C加密的文件，我得到一个坏的填充异常。如果我打开这两个文件与加密的内容，他们是不同的：

If I now try decrypting the file that was encrypted via Objective-C I get a bad padding Exception. If I open the two files with the encrypted content they are different:

Hallo Welt！用Java加密： 96 C5 CB 51 39 B5 27 FB B3 93 BF 92 18 BB 16 9B

Hallo Welt！用ObjC加密： A3 61 32 8E A5 E6 66 E0 41 64 89 25 62 D3 21 16

Hallo Welt! encrypted with Java: 96 C5 CB 51 39 B5 27 FB B3 93 BF 92 18 BB 16 9B
Hallo Welt! encrypted with ObjC: A3 61 32 8E A5 E6 66 E0 41 64 89 25 62 D3 21 16

t文件内容是否相同？我想我没有得到所有的算法的参数在两种语言相同。

Shouldn't the file content be the same? I think I don't got all the parameters for the algorithm the same in the two languages.

我需要改变Java代码以获得与Objective-C代码相同的结果，以便能够解密用Objective-C加密的一些数据。 p>

I need to alter the Java Code to get the same result as the Objective-C Code to be able to decrypt some data that was encrypted with Objective-C.

推荐答案

1. 我不会假设CCCrypt支持对输入和输出使用相同的数组。尝试使用两个不同的数组。


2. 您必须自己调整输出数组的大小（调用后numBytesEncrypted应等于16）。


3. 正如我可以看到，一个空IV信号使用ECB加密而不是CBC。

只要您的输入小于15个字节，它就不会产生任何差异， EDIT：另一个问题：

Another issue:

1. 您使用的是24字节的密钥。 AES-128需要128位= 16字节的密钥，AES-192需要192位= 24字节的密钥，AES-256需要256位= 32字节的密钥。您显式指示AES-128到CCCrypt，这意味着它忽略密钥的最后8个字节。您只是将AES指示为Java，这意味着它会查看键大小以决定要使用哪个AES变量。由于您提供了一个24字节的密钥，它使用AES-192。修复它，所以两端使用相同的算法，你应该是好的。

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