using System;

//using System.Security.Cryptography;

using Sodium;

​

public static class Program

{

    public static void Main() {

    Console.WriteLine("Libsodium detached signature string");

    // you need the library https://www.nuget.org/packages/Sodium.Core/ version 1.2.3

​

    string dataToSign = "The quick brown fox jumps over the lazy dog";

    Console.WriteLine("plaintext: " + dataToSign);

     // usually we would load the private and public key from a file or keystore

     // here we use hardcoded keys for demonstration - don't do this in real programs       

​

    Console.WriteLine("\n* * * sign the plaintext with the ED25519 private key * * ");

    byte[] privateKey = LoadEd25519PrivateKey();        

    string signatureBase64 = LibsodiumSignDetachedToBase64(privateKey, dataToSign);

    Console.WriteLine("signature (Base64): " + signatureBase64);

​

    Console.WriteLine("* * * verify the signature against the plaintext with the ED25519 public key * * *");

    byte[] publicKey = LoadEd25519PublicKey();

    bool signatureVerified = LibsodiumVerifyDetachedFromBase64(publicKey, dataToSign, signatureBase64);

    Console.WriteLine("signature (Base64): " + signatureBase64);

    Console.WriteLine("signature (Base64) verified: " + signatureVerified); 

}

    static string LibsodiumSignDetachedToBase64(byte[] privateKey, string dataToSign){

        byte[] data = System.Text.Encoding.UTF8.GetBytes(dataToSign);       

        byte[] signature = PublicKeyAuth.SignDetached(data, privateKey);

        return Base64Encoding(signature);

    }

    static bool LibsodiumVerifyDetachedFromBase64(byte[] publicKey, string dataToSign, string signatureBase64){

        byte[] data = System.Text.Encoding.UTF8.GetBytes(dataToSign);       

        byte[] signature = Base64Decoding(signatureBase64);

        return PublicKeyAuth.VerifyDetached(signature, data, publicKey);

    }   

    private static byte[] LoadEd25519PrivateKey() {

        // this is a sample key - don't worry !

        return Base64Decoding("Gjho7dILimbXJY8RvmQZEBczDzCYbZonGt/e5QQ3Vro2sjTp95EMxOrgEaWiprPduR/KJFBRA+RlDDpkvmhVfw==");

    }

    private static byte[] LoadEd25519PublicKey() {

        // this is a sample key - don't worry !

        return Base64Decoding("NrI06feRDMTq4BGloqaz3bkfyiRQUQPkZQw6ZL5oVX8=");

    }

    private static string Base64Encoding(byte[] input) {

        return Convert.ToBase64String(input);

    }

​

    private static byte[] Base64Decoding(String input) {

        return Convert.FromBase64String(input);

    }

}