Question

I am trying to use larger block size for the AES Encryption:

private static void EncryptFile(string inFile, RSACryptoServiceProvider rsaPublicKey)
{
    using (AesCryptoServiceProvider aes = new AesCryptoServiceProvider())
    {
        // Create instance of AesManaged for
        // symetric encryption of the data.
        aes.KeySize = 256;

        // Allocating 64K
        aes.BlockSize = 8 * 1024 * 64; 
    }
}

and hitting the following exception:

System.Security.Cryptography.CryptographicException was unhandled
Message=Specified block size is not valid for this algorithm.
Source=mscorlib StackTrace:
at System.Security.Cryptography.SymmetricAlgorithm.set_BlockSize(Int32
value)
at ConsoleApplication4.Program.EncryptFile(String inFile, RSACryptoServiceProvider rsaPublicKey) in
C:\Projects\ConsoleApplication4\Program.cs:line 117

I sure am missing somehting ovbious, any clue?

Answer 1

It appears that AES only supports block size equal to 128. It appears that you can get around this by processing your data as multiple blocks.

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