sharp-chat/SharpChat/Extensions.cs

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

namespace SharpChat {
    public static class Extensions {
        public static string GetSignedHash(this string str, string key = null) {
            return Encoding.UTF8.GetBytes(str).GetSignedHash(key);
        }

        public static string GetSignedHash(this byte[] bytes, string key = null) {
            key ??= File.Exists("login_key.txt") ? File.ReadAllText("login_key.txt") : "woomy";

            StringBuilder sb = new();

            using(HMACSHA256 algo = new(Encoding.UTF8.GetBytes(key))) {
                byte[] hash = algo.ComputeHash(bytes);

                foreach(byte b in hash)
                    sb.AppendFormat("{0:x2}", b);
            }

            return sb.ToString();
        }

        public static string GetIdString(this byte[] buffer) {
            const string id_chars = "abcdefghijklmnopqrstuvwxyz0123456789-_ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            StringBuilder sb = new();
            foreach(byte b in buffer)
                sb.Append(id_chars[b % id_chars.Length]);
            return sb.ToString();
        }
    }
}