Generate "Sign in with Apple" client_secret using .NET Core (C#)

Program.cs

using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Security.Cryptography;

using Microsoft.IdentityModel.Tokens;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            const string aud = "https://appleid.apple.com";

            const string kid = "0000000000"; // Key ID
            const string iss = "0000000000"; // Team ID
            const string sub = "ServiceId"; // Client ID (Service ID)
            const string privateKey = ""; // Private Key (Base64 Encode)

            var ecdsa = ECDsa.Create();

            ecdsa.ImportPkcs8PrivateKey(Convert.FromBase64String(privateKey), out _);

            var securityKey = new ECDsaSecurityKey(ecdsa)
            {
                KeyId = kid
            };

            var descriptor = new SecurityTokenDescriptor
            {
                Issuer = iss,
                Audience = aud,
                Subject = new ClaimsIdentity(new[] { new Claim("sub", sub) }),
                NotBefore = DateTime.UtcNow,
                Expires = DateTime.UtcNow.AddDays(180),
                SigningCredentials = new SigningCredentials(securityKey, SecurityAlgorithms.EcdsaSha256)
            };

            var handler = new JwtSecurityTokenHandler();

            var token = handler.CreateJwtSecurityToken(descriptor);

            Console.WriteLine(handler.WriteToken(token));
        }
    }
}

This solution only for windows platform because of the "Windows CNG". I'm looking for cross platform way.

@mehmetutkuk I have same requirement. Did you find any cross platform code? If yes can you please share? Appreciate your help!! Thanks in advance!!!

@venujdv Updated. Try it.

Thank you @shibayan . It works if we create from local. If we publish into Azure Function App, it is throwing error like "400-Bad Request" "The system cannot find the file specified." Any idea? Thanks!

@venujdv did you figured out what is the problem? I have the same one and not sure what i can do

@OleksandrOsipchuk I have added "WEBSITE_LOAD_CERTIFICATES" in Azure function app configuration with dummy value. It worked. Please see below link and update here if it works. So that may it will help others in feature. Thanks!

https://stackoverflow.com/questions/46114264/x509certificate2-on-azure-app-services-azure-websites-since-mid-2017