使用AesCryptoServiceProvider解密而不使用IV

Question

I have written a BlackBerry app that uses AES encryption. I am trying to decrypt this using the AesCryptoServiceProvider in C#.

The BlackBerry code doesn't seem to use an IV which means I have nothing to pass to the AesCryptoServiceProvider.

Is it possible for me to decrypt AES without an IV, if so, how?

Answer 1

Reading the blackberry java crypto documentation, it appears you are not supposed to directly use AESEncryptionEngine. If you use it straight, you end up with ( I assume) ECB mode which results in the following encryption of an image of a penguin. don't do it.

Rather it appears that to use some secure mode of operation, you need to actually use a wrapper around the basic AESEncrypt / Decrypt Engine. You want to use the CBCEncryptionEngine to do this. Here is some sample code from here . Note that the IV is randomized on creation, so you don't need to set it or worry about reuse. Just replace DES with AES here.

// sampleDESCBCEncryption
private static int sampleDESCBCEncryption( 
    byte[] secretKey, byte[] initVector, byte[] plainText, byte[] cipherText, int
    dataLength ) 
    throws CryptoException, IOException
{
    // Create a new DES key based on the 8 bytes in the secretKey array
    DESKey key = new DESKey( secretKey );

    // Create a new initialization vector using the 8 bytes in initVector
    InitializationVector iv = new InitializationVector( initVector );

    // Create a new byte array output stream for use in encryption
    NoCopyByteArrayOutputStream out = new NoCopyByteArrayOutputStream();

    // Create a new instance of a BlockEncryptor passing in an instance of a CBC encryptor engine
    // (containing an instance of a DES encryptor engine), the initialization vector, and the
    // output stream
    BlockEncryptor cryptoStream = new BlockEncryptor( 
        new CBCEncryptorEngine( new DESEncryptorEngine( key ), iv ), out );

    // Write dataLength bytes from plainText to the CFB encryptor stream
    cryptoStream.write( plainText, 0, dataLength );
    cryptoStream.close();

    // Now copy the encrypted bytes from out into cipherText and return the length
    int finalLength = out.size();
    System.arraycopy( out.getByteArray(), 0, cipherText, 0, finalLength );
    return finalLength;
}