/* 
  Copyright 2001-2007 Markus Hahn 
  All rights reserved. See documentation for license details.  
*/

using System;
using System.Text;

namespace DG.Tool
{

    /// <summary>An easy-to-use-string encryption solution using Blowfish/CBC.</summary>
    /// <remarks>As a simple solution for developers, who want nothing more than protect
    /// single strings with a password, this class provides the necessary functionality.
    /// The password (aka as key) is hashed using the SHA-1 implementation of the .NET
    /// framework. The random number generator for the CBC initialization vector (IV)
    /// and BASE64 are used from the framework's security services.</remarks>
    public class BlowfishSimple
    {
        BlowfishCBC bfc;

        private byte[] iv;

        private byte[] IV
        {
            get
            {
                if (iv == null || iv.Length < 8)
                {
                    return Encoding.UTF8.GetBytes("Blowfish");
                }
                return iv;
            }
            set { iv = value; }
        }

        static byte[] TransformKey(String key)
        {
            UTF8Encoding ue = new UTF8Encoding();
            return ue.GetBytes(key);
        }

        /// <summary>Empty constructor. Before using the instance you MUST call Initialize(),
        /// otherwise any result or behavior is unpredictable!</summary>
        public BlowfishSimple()
        {
        }

        /// <summary>Default constructor.</summary>
        /// <param name="keyStr">The string which is used as the key material (aka as
        /// password or passphrase). Internally the UTF-8 representation of this string
        /// is used, hashed with SHA-1. The result is then a 160bit binary key. Notice
        /// that this transformation will not make weak (meaning short or easily guessable)
        /// keys any safer!</param>
        public BlowfishSimple(String keyStr)
        {
            Initialize(keyStr, null);
        }

        public BlowfishSimple(String keyStr, Byte[] iv)
        {
            Initialize(keyStr, iv);
        }

        /// <summary>Initializes the instance with a (new) key string.</summary>
        /// <param name="keyStr">The key material.</param>
        /// <see cref="BlowfishSimple(String)"/>
        public void Initialize(String keyStr, Byte[] iv)
        {
            IV = iv;
            byte[] key = TransformKey(keyStr);

            this.bfc = new BlowfishCBC(key, 0, key.Length);
            Array.Clear(key, 0, key.Length);
        }



        /// <summary>Encrypts a string.</summary>
        /// <remarks>For efficiency the given string will be UTF-8 encoded and padded to
        /// the next 8byte block border. The CBC IV plus the encrypted data will then be
        /// BASE64 encoded and  returned as the final encryption result.</remarks>
        /// <param name="plainText">The string to encrypt.</param> 
        /// <returns>The encrypted string.</returns> 
        public String Encrypt(String plainText)
        {
            return Encrypt(plainText, this.IV);
        }

        public String Encrypt(String plainText, byte[] iv)
        {
            if (string.IsNullOrEmpty(plainText)) return string.Empty;
            int txtLen = plainText.Length;
            if (txtLen % 8 != 0)
                plainText = plainText.PadRight(txtLen - txtLen % 8 + 8, ' ');
            byte[] ueData = Encoding.UTF8.GetBytes(plainText);

            int origLen = ueData.Length;

            byte[] inBuf = new byte[origLen];

            Array.Copy(ueData, 0, inBuf, 0, origLen);

            byte[] outBuf = new byte[inBuf.Length];

            this.bfc.IV = iv;

            this.bfc.Encrypt(
                inBuf,
                0,
                outBuf,
                0,
                inBuf.Length);

            String sResult = Convert.ToBase64String(outBuf);

            Array.Clear(inBuf, 0, inBuf.Length);

            return sResult;
        }

        /// <summary>Decrypts a string which was formely generated by the Encrypt()
        /// method and a particular key.</summary>        
        /// <remarks>The string has to be decrypted with the same key, otherwise the
        /// result will be simply garbage. If you want to check if the key is the right
        /// one use the VerifyKey() method.</remarks>
        /// <param name="cipherText">The string to decrypt.</param> 
        /// <returns>The decrypted string, or null on error (usually caused by a wrong
        /// key passed in).</returns> 

        public String Decrypt(String cipherText)
        {
            return Decrypt(cipherText, this.IV);
        }

        public String Decrypt(String cipherText, byte[] iv)
        {
            byte[] cdata;

            try
            {
                cdata = Convert.FromBase64String(cipherText);
            }
            catch (FormatException)
            {
                return null;
            }

            this.bfc.SetIV(iv, 0);

            byte[] outBuf = new byte[cdata.Length];

            int dataAbs = outBuf.Length;

            this.bfc.Decrypt(
                cdata,
                0,
                outBuf,
                0,
                dataAbs);

            return Encoding.UTF8.GetString(outBuf);
        }
    }
}