How Create text file with encryption text. Samples and examples

This resource gives us knowledge of how to create text file with particular path which is static in this resource but we can make it dynamic. And write string in that text file with

encrypted formate. And when we need at that time we will decrypt it and then read it. here is the code of Encryption and Decryption using Rijndael Algorithm.

First of all we have to add Namespace like


using System.Security;
using System.Security.Cryptography;
using System.Runtime.InteropServices;
using System.Text.RegularExpressions;
using System.IO;
using System.Configuration;
using System.Net;

Now we will see how to create text with encrypted string file in specific folder.


           string localComputerName = Dns.GetHostName();
            IPHostEntry ip = Dns.GetHostEntry(localComputerName);
            string localIPAddress = ip.AddressList[1].ToString();

            string filepath = Application.StartupPath + "\\BinUsers.dll";
            FileStream fs = null;
            if (!File.Exists(filepath))
            {
                string extension = Path.GetExtension(filepath);
                filepath.Replace(extension, ".txt");
                filepath = Application.StartupPath + "\\BinUsers.txt";
                using (fs = File.Create(filepath))
                {

                }
                using (StreamWriter sw = new StreamWriter(filepath))
                {

                    string finalstr = EncryptString(localIPAddress, "password");
                    sw.Write(finalstr);
                }
            FileInfo f1 = new FileInfo(filepath);
            f1.MoveTo(Path.ChangeExtension(filepath, ".dll"));
            }

here i am writing ip address of the localcomputer so in Above Code first line means Localcomputername gets the Computer name and through IPHostEntry we can get the IP address of the local computer. And the variable filepath stores the path of the file created or will be create. Here file's extension is .dll so we have to change it into .txt.
and then through FileStream we will create text file and then Through StreamWriter we will write IP address in that file but before writing anything we will encrypt the OP Address and then write the file. For Getting IPAddress below code is used


            string localComputerName = Dns.GetHostName();
            IPHostEntry ip = Dns.GetHostEntry(localComputerName);
            string localIPAddress = ip.AddressList[1].ToString();

And this code used to create text file


            string filepath = Application.StartupPath + "\\BinUsers.dll";
            FileStream fs = null;
            if (!File.Exists(filepath))
            {
                string extension = Path.GetExtension(filepath);
                filepath.Replace(extension, ".txt");
                filepath = Application.StartupPath + "\\BinUsers.txt";
                using (fs = File.Create(filepath))
                {

                }

And this code used to write the string in text file with encryption


using (StreamWriter sw = new StreamWriter(filepath))
                {

                    string finalstr = EncryptString(localIPAddress, "password");
                    sw.Write(finalstr);
                }

Decrypt string

To decrept the string of the text file below code is used


fileLoc = Application.StartupPath + "\\BinUsers.txt";
 using (TextReader tr = new StreamReader(fileLoc))
                {
                    TextOfFile = DecryptString(tr.ReadLine(),"password")+",";
                }

Private Functions


public string EncryptString(string Text, string Password)
        {
            byte[] Bytes = System.Text.Encoding.Unicode.GetBytes(Text);
            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,
            new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
            byte[] encryptedbyte = Encrypt(Bytes, pdb.GetBytes(32), pdb.GetBytes(16));
            return Convert.ToBase64String(encryptedbyte);
        }

In Above code we pass two string
1) Text : This text means which we want to encrypt.
2) Password : this means password to decrypt.



 public static byte[] Encrypt(byte[] Data, byte[] Keybyte, byte[] IVByte)
        {
            MemoryStream mstrm = new MemoryStream();
            Rijndael algo = Rijndael.Create();
            algo.Key = Keybyte;
            algo.IV = IVByte;
            CryptoStream cs = new CryptoStream(mstrm, algo.CreateEncryptor(), CryptoStreamMode.Write);
            cs.Write(Data, 0, Data.Length);
            cs.Close();
            byte[] encryptedByte = mstrm.ToArray();
            return encryptedByte;
        }

In Above function we use Rijndael Algorithm for encryption. And this function returns EncryptedBytes.

Through Above two function we can Encrypt the string which is passed. Now will see How to Decrypt that Encrypted data.


public string DecryptString(string EncText, string Password)
        {
            byte[] EncBytes = Convert.FromBase64String(EncText);
            PasswordDeriveBytes pdb = new PasswordDeriveBytes(Password,
            new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
            byte[] decryptedbutes = Decrypt(EncBytes, pdb.GetBytes(32), pdb.GetBytes(16));
            return System.Text.Encoding.Unicode.GetString(decryptedbutes);
        }

In Above Code we can see that we passed the encryption string and password which is we had given while Encryption.


public static byte[] Decrypt(byte[] cipherByte, byte[] Keybyte, byte[] IVbyte)
        {
            MemoryStream mstrm = new MemoryStream();
            Rijndael algo = Rijndael.Create();
            algo.Key = Keybyte;
            algo.IV = IVbyte;
            CryptoStream cstrm = new CryptoStream(mstrm, algo.CreateDecryptor(), CryptoStreamMode.Write);
            cstrm.Write(cipherByte, 0, cipherByte.Length);
            cstrm.Close();
            byte[] decryptedbytes = mstrm.ToArray();
            return decryptedbytes;
        }

Above Two functions gives the out put of Decrepted string. When Decreption is over we can use that string in anywhere in our project.

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How Create text file with encryption text.

Decrypt string

Private Functions

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