Load RSA public key from RSAParams

Question

I have a requirement to generate RSA key pair in C# and then store public key in the database to be used in JWK format later on.

But I am unable to get the string from the RSAParams.Modulus.

I have tried UTF8,UTF32 and general encoding but still it is not showing.

Here is the code below from MSDN site.

try
        {
            // Create a new RSACryptoServiceProvider object.
            using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
            {

                //Export the key information to an RSAParameters object.
                //Pass false to export the public key information or pass
                //true to export public and private key information.
                RSAParameters RSAParams = RSA.ExportParameters(true);

                byte[] modulus = RSAParams.Modulus;
                var str = System.Text.Encoding.UTF8.GetString(RSAParams.Modulus);
                Console.WriteLine(str);
                Console.ReadKey();

            }
        }
        catch (CryptographicException e)
        {
            //Catch this exception in case the encryption did
            // not succeed.
            Console.WriteLine(e.Message);
        }

Thank you.

The public key is a combination of `Exponent` and `Modulus`, so you'll have to serialize both. What format do you expect your output to be in? — a-ctor, Jun 18 '20 at 10:42
Also take a look at [this](https://stackoverflow.com/a/5845191) answer since you are currently storing the generated key on the file system. — a-ctor, Jun 18 '20 at 10:46
Thank you I ended up using XML to read the value .. not sure it is proper way to do or not. string publicKeyXML = RSA.ToXmlString(false); XDocument doc = XDocument.Parse(publicKeyXML); foreach (XElement element in doc.XPathSelectElement("//RSAKeyValue").Descendants()) { string value = element.Value; } — snowflakes74, Jun 18 '20 at 10:55

score 1 · Answer 1 · answered Jun 18 '20 at 11:07

I assume that you want your output to be base64. Then you can use Convert.ToBase64String to convert the Exponent and the Modulus parts of the RSA key:

var exponent = Convert.ToBase64String(rsaParams.Modulus);
var modulus = Convert.ToBase64String(rsaParams.Exponent);

That is the same thing that your solution in the comments does (see source code of .ToXmlString) but it does require the detour over XML.

Load RSA public key from RSAParams

1 Answers1