Encryption/Decryption of a file

Here Sample code
--------------------

using System;  
using System.Collections.Generic;  
using System.Text;  
using System.Security.Cryptography;  
using System.IO;  
 
namespace BHI.Rats  
{  
    ///

  
    /// RatsEncryptionManager is responsible for encrypting and decrypting the files.  
    ///

  
    public static class  RatsEncryptionManager  
    {  
        private const string passKey = "c0ntr0l1";  
 
        ///

  
        /// Decrypts the input file (strInputFileName) and creates a new decrypted file (strOutputFileName)  
        ///

  
        /// input file name  
        /// output file name  
        public static void DecryptFiletoFile(string strInputFileName, string strOutputFileName)  
        {  
            string strFileData = "";  
            using (FileStream inputStream = new FileStream(strInputFileName, FileMode.Open, FileAccess.Read))  
            {  
                DESCryptoServiceProvider cryptic = new DESCryptoServiceProvider();  
 
                cryptic.Key = ASCIIEncoding.ASCII.GetBytes(passKey);  
                cryptic.IV = ASCIIEncoding.ASCII.GetBytes(passKey);  
 
                CryptoStream crStream = new CryptoStream(inputStream, cryptic.CreateDecryptor(), CryptoStreamMode.Read);  
 
                StreamReader reader = new StreamReader(crStream);  
 
                strFileData = reader.ReadToEnd();  
 
                reader.Close();  
                inputStream.Close();  
            }  
 
            if (File.Exists(strOutputFileName))  
            {  
                File.Delete(strOutputFileName);  
            }  
            using (StreamWriter outputStream = new StreamWriter(strOutputFileName))  
            {  
                outputStream.Write(strFileData, 0, strFileData.Length);  
 
                outputStream.Close();  
            }  
 
        }  
        ///

  
        /// Encrypts the input file(strInputFileName) and creates a new encrypted file(strOutputFileName)  
        ///

  
        /// input file name  
        /// output file name  
        public static void EncryptFiletoFile(string strInputFileName, string strOutputFileName)  
        {  
            byte[] fileBuffer;  
 
            using (FileStream inputStream = new FileStream(strInputFileName, FileMode.Open, FileAccess.Read))  
            {  
                fileBuffer = new byte[inputStream.Length];  
 
                inputStream.Read(fileBuffer, 0, fileBuffer.GetLength(0));  
 
 
                inputStream.Close();  
            }  
            if (File.Exists(strOutputFileName))  
            {  
                File.Delete(strOutputFileName);  
            }  
            using (FileStream outputStream = new FileStream(strOutputFileName, FileMode.OpenOrCreate, FileAccess.ReadWrite))  
            {  
                DESCryptoServiceProvider cryptic = new DESCryptoServiceProvider();  
 
                cryptic.Key = ASCIIEncoding.ASCII.GetBytes(passKey);  
                cryptic.IV = ASCIIEncoding.ASCII.GetBytes(passKey);  
 
                CryptoStream crStream = new CryptoStream(outputStream, cryptic.CreateEncryptor(), CryptoStreamMode.Write);  
 
                crStream.Write(fileBuffer, 0, fileBuffer.Length);  
 
                crStream.Close();  
            }  
        }  
        ///

  
        /// Encrypts the input string and creates a new encrypted file(strOutputFileName)  
        ///

  
        /// input string name  
        /// output file name  
        public static void EncryptStringtoFile(string strInputString, string strOutputFileName)  
        {  
            if (File.Exists(strOutputFileName))  
            {  
                File.Delete(strOutputFileName);  
            }  
            using (FileStream outputStream = new FileStream(strOutputFileName, FileMode.OpenOrCreate, FileAccess.ReadWrite))  
            {  
                DESCryptoServiceProvider cryptic = new DESCryptoServiceProvider();  
 
                cryptic.Key = ASCIIEncoding.ASCII.GetBytes(passKey);  
                cryptic.IV = ASCIIEncoding.ASCII.GetBytes(passKey);  
 
                CryptoStream crStream = new CryptoStream(outputStream, cryptic.CreateEncryptor(), CryptoStreamMode.Write);  
 
                byte[] buffer = ASCIIEncoding.ASCII.GetBytes(strInputString);  
 
                crStream.Write(buffer, 0, buffer.Length);  
 
                crStream.Close();  
            }  
        }  
        ///

  
        /// Decrypts the input file (strInputFileName) and creates a new decrypted file (strOutputFileName)  
        ///

  
        /// input file name  
        public static string DecryptFiletoString(string strInputFileName)  
        {  
            string strFileData = "";  
            using (FileStream inputStream = new FileStream(strInputFileName, FileMode.Open, FileAccess.Read))  
            {  
                DESCryptoServiceProvider cryptic = new DESCryptoServiceProvider();  
 
                cryptic.Key = ASCIIEncoding.ASCII.GetBytes(passKey);  
                cryptic.IV = ASCIIEncoding.ASCII.GetBytes(passKey);  
 
                CryptoStream crStream = new CryptoStream(inputStream, cryptic.CreateDecryptor(), CryptoStreamMode.Read);  
 
                StreamReader reader = new StreamReader(crStream);  
 
                strFileData = reader.ReadToEnd();  
 
                reader.Close();  
                inputStream.Close();  
            }  
 
            return strFileData;  
        }  
    }  
}

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