How to implement apple token based push notifications (using p8 file) in C#?

Question

For an app with some kind of chat based features I want to add push notification support for receiving new messages. What I want to do is use the new token based authenticat

Answer 1

private string GetToken()
    {
        var dsa = GetECDsa();
        return CreateJwt(dsa, "keyId", "teamId");
    }
    
    private ECDsa GetECDsa()
    {
        using (TextReader reader = System.IO.File.OpenText("AuthKey_xxxxxxx.p8"))
        {
        var ecPrivateKeyParameters =
            (ECPrivateKeyParameters)new Org.BouncyCastle.OpenSsl.PemReader(reader).ReadObject();

        var q = ecPrivateKeyParameters.Parameters.G.Multiply(ecPrivateKeyParameters.D).Normalize();
        var qx = q.AffineXCoord.GetEncoded();
        var qy = q.AffineYCoord.GetEncoded();
        var d = ecPrivateKeyParameters.D.ToByteArrayUnsigned();

        // Convert the BouncyCastle key to a Native Key.
        var msEcp = new ECParameters {Curve = ECCurve.NamedCurves.nistP256, Q = {X = qx, Y = qy}, D = d};
        return ECDsa.Create(msEcp);
        }
    }
    
    private string CreateJwt(ECDsa key, string keyId, string teamId)
    {
        var securityKey = new ECDsaSecurityKey(key) { KeyId = keyId };
        var credentials = new SigningCredentials(securityKey, SecurityAlgorithms.EcdsaSha256);

        var descriptor = new SecurityTokenDescriptor
        {
            IssuedAt = DateTime.Now,
            Issuer = teamId,
            SigningCredentials = credentials,
            
        };

        var handler = new JwtSecurityTokenHandler();
        var encodedToken = handler.CreateEncodedJwt(descriptor);
        return encodedToken;
    }