2.How can I generate the key and how can it be validated by

You can generate a Unique Key with the following code.

        public static string GenerateUniqueId()
        {
            long i = 1;
            foreach (byte b in Guid.NewGuid().ToByteArray())
            {
                i *= ((int)b + 1);
            }
            return string.Format("{0:x}", i - DateTime.Now.Ticks);