[CRYPTO]Use RSA keyset generated by .NET sn.exe tool

[CRYPTO]Use RSA keyset generated by .NET sn.exe tool


I’ve found some public articles about how to manually extract RSA keyset from the snk file generated by .NET sdk tool “sn.exe”.


#Strong Name Tool (Sn.exe) 



And some community guys have also encountered some problems manually use the sn.exe generated snk file to get RSA keyinfo and perform encryption/signing. By doing some research on this, I found that it is really not good idea to use SN.EXE generated key file for our RSA crypto task. Here are some reasons:


l  Sn.exe generated key file is of an undocumented format. Microsoft doesn’t expect the developers to directly load RSA keyset from this file.


l  Sn.exe generated keyset is “signature” keyset, therefore, it is used for data signing and verifying


l  The reasonable usage of SN.exe generated keyset is for digital signing against .NET assembly(strong-name signing).



However, if you do want to use the RSA keyset generated by sn.exe(-k), you can consider the following means:


1.generate snk file via “sn.exe -k” command:


sn.exe -k MyTestRSA_SNKContainer


2.install the keyset into a KeyContainer via “sn.exe -i” command:


sn.exe -i MyTestRSA.snk MyTestRSA_SNKContainer


3.Read keyset from KeyContainer(instead of snk file):




static void Use_SNKContainer()


            RSACryptoServiceProvider RSA = null;


            string container = “MyTestRSA_SNKContainer”;

            CspParameters cp1 = new CspParameters();


            cp1.Flags = CspProviderFlags.UseMachineKeyStore | CspProviderFlags.UseExistingKey;

            cp1.KeyNumber = (int)KeyNumber.Signature;

            cp1.KeyContainerName = container;

            RSA = new RSACryptoServiceProvider(cp1);


            //perform signing or verification




Also, if you want to generate RSA keyset programmatically in .NET code, here are some samples:


#How to generate key pairs, encrypt and decrypt data with .NET (C#)



#Generating Keys for Encryption and Decryption 






Comments (3)

  1. Norm says:


    I’ve got a "Key not valid for use in specified state." error on ToXmlString. But this only happens when "bPrivate" = true – i.e. export private key as well.

    cspParams = new CspParameters();

    cspParams.Flags = CspProviderFlags.UseMachineKeyStore | CspProviderFlags.UseExistingKey;

    cspParams.KeyNumber = (int)KeyNumber.Signature;

    cspParams.KeyContainerName = strContainerName;

    rsaProvider = new RSACryptoServiceProvider(cspParams);

    // Export key

    strKey = rsaProvider.ToXmlString(bPrivate);

    Any idea? Thanks!

  2. Norm says:

    Do I need to make my certificate "Exportable" somehow?


    I added "Certificates" add-in to my MMC, I can’t find the container that I supposedly imported using:

      sn.exe -i MyTestRSA.snk MyTestRSA_SNKContainer

    And even if I found it how can I make it "Exportable"? I’m already an Administrator when I got "Key not valid for use in specified state."