#region License Information

// Copyright (c) 2005 - 2009, Allan Spartacus Mangune (allan@owlpal.com)

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without modification, 

// are permitted provided that the following conditions are met:

//

// * Redistributions of source code must retain the above copyright notice, this list 

//   of conditions and the following disclaimer.

//

// * Redistributions in binary form must reproduce the above copyright notice, this list of 

//   conditions and the following disclaimer in the documentation and/or other materials provided 

//   with the distribution.

//

// * Neither the name of Owlpal nor the names of its contributors may be used to endorse or 

//   promote products derived from this software without specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS 

// OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 

// FITNESS FOR AllowHtmlInComment PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS 

// BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 

// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 

// OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 

// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE 

// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 

#endregion

using System;

using System.Security.Cryptography;



namespace Owlpal.Security

{

	public sealed class SaltedHash 

	{

		#region Members

		private readonly string salt;

		private readonly string hash;

		private const int saltLength = 20;

		#endregion



		#region Properties

        /// <summary>

        /// 

        /// </summary>

        public string Hash

        {

            get { return this.hash; }

        }

        

        /// <summary>

        /// 

        /// </summary>

        public string Salt 

		{ 

			get { return this.salt; } 

		}

        #endregion



		#region Public Members

		/// <summary>

		/// 

		/// </summary>

		/// <param name="password"></param>

		/// <returns></returns>

        public SaltedHash Create(string password) 

		{

			string salt = CreateSalt();

			string hash = ComputeHash(salt, password);

			return new SaltedHash(salt, hash);

		}



        /// <summary>

        /// 

        /// </summary>

        /// <param name="salt"></param>

        /// <param name="hash"></param>

        /// <returns></returns>

		public SaltedHash Create(string salt, string hash) 

		{

			return new SaltedHash(salt, hash);

		}



        /// <summary>

        /// 

        /// </summary>

        /// <param name="password"></param>

        /// <param name="salt"></param>

        /// <returns></returns>

		public bool IsValid(string password, string salt) 

		{

            return this.hash.Equals(ComputeHash(salt, password));

		}



        /// <summary>

        /// 

        /// </summary>

        /// <param name="password"></param>

        /// <returns></returns>

        public bool IsValid(string password)

        { 

            return this.hash.Equals(ComputeHash(this.salt, password));

        }

		#endregion



		#region Private Members

		/// <summary>

        /// 

        /// </summary>

        /// <returns></returns>

		private string CreateSalt() 

		{

			return Convert.ToBase64String(CreateRandomBytes(saltLength));

		}



        /// <summary>

        /// 

        /// </summary>

        /// <param name="len"></param>

        /// <returns></returns>

		private byte[] CreateRandomBytes(int len) 

		{

			byte[] randomBytes = new byte[len];

			new  RNGCryptoServiceProvider().GetBytes(randomBytes);

			return randomBytes;

		}



        /// <summary>

        /// 

        /// </summary>

        /// <param name="salt"></param>

        /// <param name="password"></param>

        /// <returns></returns>

		private string ComputeHash(string salt, string password) 

		{

			return Convert.ToBase64String(new SHA256CryptoServiceProvider()

                .ComputeHash(System.Text.Encoding.UTF8.GetBytes(salt + password)));

		}

		#endregion



        #region Contructors

        /// <summary>

        /// 

        /// </summary>

        public SaltedHash()

        {



        }



        /// <summary>

        /// 

        /// </summary>

        /// <param name="salt"></param>

        /// <param name="hash"></param>

        public SaltedHash(string salt, string hash)

        {

            this.salt = salt;

            this.hash = hash;

        }

        #endregion

    }

}