使用软件分发RSA公钥的最简单方法是什么？

Question

I'm working on some software that exchanges XML documents with a server. The server signs the XML using XMLDSIG and the client should verify the signature before trusting the XML. I'm using RSACryptoServiceProvider to do this. The XML is signed, but not encrypted.

I'm following the basic procedure explained in:
How to Sign XML Documents with Digital Signatures
How to Verify the Digital Signatures of XML Documents

This requires that the client software has the public key available. I want the distribution of the client software to be as simple as possible and I don't want the client to have to deal with certificates. The pair of documents referenced above conveniently skirt around the subject of distributing the public key, simply stating that the user "needs to have the same key". I don't particularly want the end user to even be aware that they have a public key, so asking them to mess around with certificates is out of the question. Since the public key is public, what I would like to do is somehow embed it within the client software. As I see it, my options are:

• Install the public key during the setup process
• Somehow embed the public key into the software itself, possibly within the App.config file

Is this feasible in practice? What is the simplest way of achieving this that doesn't require any user interaction or awareness?

Answer 1

You don't have to distribute the certificate. One of common approaches is to include the certificate in the signed document, in the KeyInfo/X509Data node.

The validation can use the embedded certificate easily and the only required infrastructure element at the client side is the certificate thumbprint and subject name. In other words, client validates the document using included certificate and then easily checks the certificate agaist the subject name and thumbprint. In case of a match, there is the assumption that a correct certificate has been provided.

Read more about technical details in one of my blog entries (this is a 3 part tutorial so you can also take a look at all other entries). Anyway, no importing certificates and no including certificates with your software, rather you have two string configuration parameters.

The embedded certificate inside the XmlDsigned document has a const size and usually the overhead is neglectable.

http://www.wiktorzychla.com/2012/12/interoperable-xml-digital-signatures-c.html

http://www.wiktorzychla.com/2012/12/interoperable-xml-digital-signatures-c_20.html

Answer 2

Am not sure what problem you're facing without seeing your code but, could this answer from Ji Zhou help?

public static void Main()
 {
     try
     {        //initialze the byte arrays to the public key information.
         byte[] PublicKey = {214,46,220,83,160,73,40,39,201,155,19,202,3,11,191,178,56,
                            74,90,36,248,103,18,144,170,163,145,87,54,61,34,220,222,
                            207,137,149,173,14,92,120,206,222,158,28,40,24,30,16,175,
                            108,128,35,230,118,40,121,113,125,216,130,11,24,90,48,194,
                            240,105,44,76,34,57,249,228,125,80,38,9,136,29,117,207,139,
                            168,181,85,137,126,10,126,242,120,247,121,8,100,12,201,171,
                            38,226,193,180,190,117,177,87,143,242,213,11,44,180,113,93,
                            106,99,179,68,175,211,164,116,64,148,226,254,172,147};

        //Values to store encrypted symmetric keys.
         byte[] EncryptedSymmetricKey;
         byte[] EncryptedSymmetricIV;

        //Create a new instance of RSACryptoServiceProvider.
         RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();

        //Get an instance of RSAParameters from ExportParameters function.
         RSAParameters RSAKeyInfo = RSA.ExportParameters(false);

        //Set RSAKeyInfo to the public key values. 
         RSAKeyInfo.Modulus = PublicKey;
         //Import key parameters into RSA.
         RSA.ImportParameters(RSAKeyInfo);

        //Create a new instance of the RijndaelManaged class.
         RijndaelManaged RM = new RijndaelManaged();

        //Encrypt the symmetric key and IV.
         EncryptedSymmetricKey = RSA.Encrypt(RM.Key, false);
         EncryptedSymmetricIV = RSA.Encrypt(RM.IV, false);

        Console.WriteLine("RijndaelManaged Key and IV have been encrypted with RSACryptoServiceProvider.");
     }
     catch (CryptographicException e)
     {
         Console.WriteLine(e.Message);
     }
 }