Demonstrates calculating a strong name token from a public key

StrongNameTokenFromPublicKey.cs

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace ConsoleApp43
{
    static class Program
    {
        static void Main(string[] args)
        {
            byte[] publicKey = File.ReadAllBytes(@"C:\git\Nerdbank.GitVersioning\src\NerdBank.GitVersioning.Tests\Keys\public.snk");
            byte[] token = StrongNameTokenFromPublicKey(publicKey);
            Console.WriteLine($"Public key: {publicKey.AsHex()}");
            Console.WriteLine($"Public key token: {token.AsHex()}");
        }

        private static byte[] StrongNameTokenFromPublicKey(byte[] publicKey)
        {
            // Reverse engineered from the implementation found here:
            // https://github.com/dotnet/coreclr/blob/2efbb9282c059eb9742ba5a59b8a1d52ac4dfa4c/src/strongname/api/strongname.cpp#L387
            const int cbToken = 8;
            var sha1Algorithm = SHA1.Create();
            byte[] hash = sha1Algorithm.ComputeHash(publicKey);
            int cbHashLengthMinusTokenSize = hash.Length - cbToken;
            byte[] token = new byte[cbToken];
            for (int i = 0; i < cbToken; i++)
            {
                token[cbToken - (i + 1)] = hash[i + cbHashLengthMinusTokenSize];
            }

            return token;
        }

        static string AsHex(this byte[] buffer)
        {
            var sb = new StringBuilder(buffer.Length * 2);
            for (int i = 0; i < buffer.Length; i++)
            {
                sb.AppendFormat("{0:x2}", buffer[i]);
            }

            return sb.ToString();
        }
    }
}

Reverse engineered from the implementation found here:
https://github.com/dotnet/coreclr/blob/2efbb9282c059eb9742ba5a59b8a1d52ac4dfa4c/src/strongname/api/strongname.cpp#L387