iPhone AES encryption issue

I use following code to encrypt using AES.

- (NSData*)AES256EncryptWithKey:(NSString*)key theMsg:(NSData *)myMessage {

    // '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 = [myMessage 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) */,
                                          [myMessage bytes], dataLength, /* input */
                                          buffer, bufferSize, /* output */
                                          &numBytesEncrypted);

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

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

However the following code chunk returns null if I tried to print the encryptmessage variable. Same thing applies to decryption as well. What am I doing wrong here?

 NSData *encrData = [self AES256EncryptWithKey:theKey theMsg:myMessage];
 NSString *encryptmessage = [[NSString alloc] initWithData:encrData encoding:NSUTF8StringEncoding];

Thank you

try using

size_t bufferSize= dataLength + kCCBlockSizeAES256;

instead of

size_t bufferSize = dataLength + kCCBlockSizeAES128;