RSA.ImportCspBlob: Bad Provider

Question

Hi all, i am porting a code from C++ to C# that uses OpenSSL and RSA. Basically i have the private key (1024 bits) and i want to decrypt a chunk of data. The key and the chunk are the same i use in rsa_decrypt(), but i'm gettig Bad Provider from ImportCspBlob(); Here is the code:


public static byte[] DecryptRSA(byte[] data, byte[] key)
        {
            byte[] decrypted = null;

            try
            {
                RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
                rsa.ImportCspBlob(key);
                decrypted = rsa.Decrypt(data, false);
            }
            catch
            {
            }

            return decrypted;
        }

Am i doing something wrong?

Answer 1

Hello, Caian
You are doing nothing wrong in your current code, if there is nothing wrong with your key. I doubt there is something wrong with your key, Is your key is exported through the ExportCspBlob(bool) method?
Could you post your Encrypt Code here? I am not able to find any clue according such a little code.
Thanks
Chao

Answer 2

The key and the data chunk were provided for testing the final application and i don't have access to source for the encoder, but since the work involves porting the decoder from native C++ code i guess that the key was created using OpenSSL because the decorder uses OSSL libs and the key (and data) works like a charm with rsa_decrypt().

I am trying to use RSA.ImportCspBlob because it was the only method i found in C# that actually accepts a already-buit key without all that "register stuff". I assumed that a RAW key was compatible with this function.

Answer 3

Hello, Caian
If there is something wrong with your key, your provider would be wrong. So make your key right, does your converting from string to byte[] using System.Text.Encoding.ASCII.GetString method? If not please try to use this method.
Thanks
Chao

Answer 4

I tested in the C++ application myself and it works, the key is not a string, i received it as a byte array and considering the contents it's not a hex string nor a understandable string.

Another possibility is the key is not in a Blob format, if so, is there any other way to set a custom key to the RSA Service?

Thanks,
Caian