We have created a signature in a .Net Core web api, using X509Certificate2.GetECDsaPrivateKey on a .pfx certificate file, and need to verify this signature in our Xamarin Android app, using the public key (.crt). I can run the code on a normal Windows .Net Framework 4.6.1 app and it works. If I change the Framework version to anything lower, my app doesn't compile, as the GetECDsaPublicKey method was only implemented in 4.6.1. In my Xamarin app, I can compile the app and it runs, but as soon as I reach the line that executes the GetECDsaPublicKey method, I get a NotImplemented exception. There is literally no information on this on the internet, apart from the Microsoft documentation, which doesn't give much in any case. Can anyone shed any light onto why this error occurs? Here are the few lines of code to load the certificate and verify the signature (I've taken out some unnecessary error checking code):
string FileName = "public_key.crt";
string certPath = System.IO.Path.Combine(System.Environment.GetFolderPath(System.Environment.SpecialFolder.Personal), FileName);
System.Security.Cryptography.X509Certificates.X509Certificate2 certificate = new System.Security.Cryptography.X509Certificates.X509Certificate2(certPath);
System.Security.Cryptography.ECDsa eCDsa = certificate.GetECDsaPublicKey(); // This line causes the exception
Even just executing this line, gives the same error:
System.Security.Cryptography.ECDsa eCDsa = System.Security.Cryptography.ECDsa.Create();
