MtsIdNet

dotnet add package MtsIdNet

using MtsIdNet;

var client = new MtsIdClient(httpClient, new MtsIdClientOptions
{
    ClientId = "mts_test_service",
    SigningKey = MtsKeys.RsaFromPem(File.ReadAllText("sp-private.pem")),
    SigningKeyId = "rsa_kid",
    NotificationUri = "https://service-provider.io/notification_uri/",
});

// Publish your JWKS so Mobile ID can verify the signed request:
string jwksJson = client.BuildPublishedJwks().ToJson();

// Start a server-initiated (CIBA) authentication:
var result = await client.SiAuthorizeAsync(new RequestObjectParameters
{
    Scope = $"{MtsIdConstants.Scopes.OpenId} {MtsIdConstants.Scopes.Authn}",
    LoginHint = RequestObjectParameters.ForMsisdn("+7 915 000 00 00"),
    ClientNotificationToken = Guid.NewGuid().ToString(),
});