Private methods

License.cs

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

namespace License
{
    public class LicenseServiceImpl
    {
        public String GenerateLicense(String secret)
        {
            var hashBytes = this.ComputeSecretHash(secret);

            return Convert.ToBase64String(hashBytes);
        }

        public Boolean ValidateLicense(String license, String secret)
        {
            var hashBytes = this.ComputeSecretHash(secret);

            var hashBase64Str = Convert.ToBase64String(hashBytes);

            return license == hashBase64Str;
        }

        private byte[] ComputeSecretHash(String secret)
        {
            SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();

            var secretBytes = Encoding.UTF8.GetBytes(secret);

            var hashBytes = sha1.ComputeHash(secretBytes);

            return hashBytes;
        }
    }
}