用C#编写一个ReSharper的Keygen

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ReSharperKeygen
{
    public class KeyGen
    {
        private const string PrivateKey = "348*********080286*********0936*********194468";
        private const string PublicKey = "348*********802*********215865425*********16793";

        public string CompanyName { get; set; }

        public string UserName { get; set; }

        public KeyGen()
        {
            CompanyName = string.Empty;
        }

        public string GetLicense()
        {
            var bigInteger = (new BigInteger(ushort.MaxValue) << 72) + new BigInteger(UserHash()) + (new BigInteger(ushort.MaxValue) << 56);
            var n = new BigInteger(PublicKey, 10);
            var exp = (new BigInteger(StringToBytesConverter.Old(UserName)) | 1).modInverse(new BigInteger(PrivateKey, 10));
            return Convert.ToBase64String(bigInteger.modPow(exp, n).getBytes());
        }

        private int UserHash()
        {
            var num = 0;
            for (var index = 0; index < UserName.Length; ++index)
                num = ((num << 7) + UserName[index]) % 65521;
            for (var index = 0; index < CompanyName.Length; ++index)
                num = ((num << 7) + CompanyName[index]) % 65521;
            return num;
        }
    }
}