jwt_test.cs

using System;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using Microsoft.IdentityModel.Tokens;

namespace JWTTest
{
    public static class Program
    {
        public static void Main()
        {
            bool x509 = true;

            SigningCredentials signingCredentials;
            EncryptingCredentials encryptingCredentials;
            if (x509)
            {
                var chosenCert = FindAnyUsableCert();

                var key = new X509SecurityKey(chosenCert);
                signingCredentials = new SigningCredentials(key, SecurityAlgorithms.RsaSha256Signature);
                encryptingCredentials = new EncryptingCredentials(key, SecurityAlgorithms.RsaOAEP,
                    SecurityAlgorithms.Aes256CbcHmacSha512);
            }
            else
            {
                var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(new string('s', 12345))); // the "s" is for "secure"
                signingCredentials = new SigningCredentials(key, SecurityAlgorithms.HmacSha256Signature);
                encryptingCredentials = new EncryptingCredentials(key, "dir", SecurityAlgorithms.Aes256CbcHmacSha512);
            }

            var securityTokenDescriptor = new SecurityTokenDescriptor
            {
                IssuedAt = DateTime.MinValue,
                NotBefore = DateTime.MinValue,
                Expires = DateTime.MaxValue,
                SigningCredentials = signingCredentials,
                EncryptingCredentials = encryptingCredentials,
            };

            var handler = new JwtSecurityTokenHandler();
            var token = handler.CreateToken(securityTokenDescriptor);
            Console.WriteLine(handler.WriteToken(token));
        }

        private static X509Certificate2 FindAnyUsableCert()
        {
            using (var certStore = new X509Store(StoreName.My, StoreLocation.CurrentUser))
            {
                certStore.Open(OpenFlags.ReadOnly);

                foreach (var cert in certStore.Certificates)
                {
                    if (cert.HasPrivateKey)
                    {
                        try
                        {
                            var privKey = cert.GetRSAPrivateKey();
                            if (privKey.KeySize >= 2048)
                            {
                                return cert;
                            }
                        }
                        catch
                        {
                            // not exportable
                        }
                    }
                }
            }

            throw new Exception("Couldn't find a usable certificate :(");
        }
    }
}