Question

我试图解密服务器发送到我的应用程序的一些AES加密数据。

为了提炼问题，我编写了一个小型java程序来模拟服务器正在做什么。它使用AES加密一些测试数据，然后将其编码为Base64：

AesCipherService cipherService  = new AesCipherService();
cipherService.setKeySize(128);

String stringKey = "2EE1F10212ADD4BE";
byte[] keyAsBytes =  stringKey.getBytes();

String text = "text to encrypt";
byte[] encryptedBytes    = cipherService.encrypt(text.getBytes(), keyAsBytes).getBytes();
String base64String      = Base64.encodeToString(encryptedBytes);
System.out.println(base64String);

// Reverse the process to check can retrieve "text to encrypt":
byte[] bytesToDecode = Base64.decode(base64String);
byte[] decryptedBytes = cipherService.decrypt(bytesToDecode, keyAsBytes).getBytes();         
String decryptedString = new String(decryptedBytes);   
System.out.println(decryptedString);

运行时，这是输出：

R5UBpP30YjX9Ae2HoPb2Rrfi5rQJY2d0ac1 + zaIX5A4 =

要加密的文字

所以我可以成功加密数据，打印出来。然后，如果我没有加密它，原始文本就会显示出来，所以这里的一切都运转正常。

现在这是我的Obj-C代码，我尝试解密从Java代码加密的数据。我已经从NetBeans IDE输出窗口复制/粘贴了加密数据作为要解密的obj-c内容的源数据：

- (void) decryptData
{
    NSData* dataToDecrypt       = [[NSData alloc] initWithBase64EncodedString: @"R5UBpP30YjX9Ae2HoPb2Rrfi5rQJY2d0ac1+zaIX5A4="  options: 0];
    NSString* key               = @"2EE1F10212ADD4BE";

    char keyPtr[kCCKeySizeAES128];
    bzero(keyPtr, sizeof(keyPtr));
    [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

    NSUInteger dataLength = [dataToDecrypt length];
    size_t bufferSize = dataLength + kCCBlockSizeAES128;
    void *buffer = malloc(bufferSize);

    size_t numBytesDecrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmAES,
                                          kCCOptionPKCS7Padding,
                                          keyPtr,
                                          kCCBlockSizeAES128,
                                          keyPtr,
                                          [dataToDecrypt bytes],
                                          dataLength,
                                          buffer,
                                          bufferSize,
                                          &numBytesDecrypted);
    if (cryptStatus == kCCSuccess) {
        NSLog(@"Success");
        NSData* unencryptedData = [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];
        Byte *unencryptedAsBytes = (Byte*)malloc(unencryptedData.length);
        memcpy(unencryptedAsBytes, [unencryptedData  bytes], unencryptedData.length);
        NSString *decryptedString = [NSString stringWithUTF8String:[unencryptedData bytes]];
        NSLog(@"%@", decryptedString);
    }
}

运行时，状态为kCCSuccess，numBytesDecrypted为32（与dataLength相同），但解密后的字符串不是“要加密的文本”，decryptedString为nil，如果我在Xcode的控制台中未加密AsBytes，则会显示：

“\一条Y | \ 376 \ 347cD * \ 320NC \ X14 \ x91C \ X88 \ 301 \ 341z \ XACA \ X11 \ 371

知道这里有什么问题吗？

Answer 1

Java加密代码生成随机IV并使用它加密前缀。为了解密，IV从加密中分离出来。

以十六进制：

key:       32454531463130323132414444344245  
iv:        479501A4FDF46235FD01ED87A0F6F646 (first 16 binary bytes of the full encryption)  
encrypted: B7E2E6B40963677469CD7ECDA217E40E (rest of binary bytes of the full encryption)  
decrypted: 7465787420746F20656E6372797074

代码：

NSData* fullEncrypted       = [[NSData alloc] initWithBase64EncodedString: @"R5UBpP30YjX9Ae2HoPb2Rrfi5rQJY2d0ac1+zaIX5A4="  options: 0];
NSData *ivData = [fullEncrypted subdataWithRange:NSMakeRange(0, kCCBlockSizeAES128)];
NSData *encryptedData = [fullEncrypted subdataWithRange:NSMakeRange(kCCBlockSizeAES128, fullEncrypted.length-kCCBlockSizeAES128)];
NSLog(@"ivData:          %@", ivData);
NSLog(@"encryptedData:   %@", encryptedData);

NSData *keyData = [@"2EE1F10212ADD4BE" dataUsingEncoding:NSUTF8StringEncoding];
NSLog(@"keyData:         %@", keyData);

NSMutableData *unencryptedData = [NSMutableData dataWithLength:encryptedData.length];
size_t numBytesDecrypted = 0;
CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                      kCCAlgorithmAES,
                                      kCCOptionPKCS7Padding,
                                      keyData.bytes, keyData.length,
                                      ivData.bytes,
                                      encryptedData.bytes, encryptedData.length,
                                      unencryptedData.mutableBytes, unencryptedData.length,
                                      &numBytesDecrypted);
if (cryptStatus == kCCSuccess) {
    NSLog(@"Success");

    unencryptedData.length = numBytesDecrypted;
    NSLog(@"unencryptedData: %@", unencryptedData);

    NSString *decryptedString = [[NSString alloc] initWithData:unencryptedData encoding:NSUTF8StringEncoding];
    NSLog(@"decryptedString: %@", decryptedString);
}

输出：

ivData:          479501a4 fdf46235 fd01ed87 a0f6f646  
encryptedData:   b7e2e6b4 09636774 69cd7ecd a217e40e  
keyData:         32454531 46313032 31324144 44344245  
Success  
unencryptedData: 74657874 20746f20 656e6372 79707400  
decryptedString: text to encrypt

无法使用使用Java

1 个答案: