?
Solved

Encrypt a file using AES encryption in C#

Posted on 2011-03-24
2
Medium Priority
?
2,935 Views
Last Modified: 2012-05-11
There are several resources in the internet which give sample code for encrypting/ decrypting a PLAINTEXT using C#, which uses RijndaelManaged or AES encryption.

I am searching for some sample code which will help me encrypt/ decrypt a file and give me another file as output. The contents of the file to be encrypted can be a PLAINTEXT, BINARY DATA or ZIPPED DATA.

Can someone help please.
0
Comment
Question by:tknayak123
2 Comments
 
LVL 86

Accepted Solution

by:
Mike Tomlinson earned 2000 total points
ID: 35209291
Here's an example where the key to encrypt/decrypt is entered by the user into textBox1:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

using System.Security.Cryptography;
using System.IO;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        // Make a random string to base your Initialization Vector from:  *This is NOT the password or key!!!
        private const string _IV = "stick some string in here"; // thus must be the same to decrypt your encrypted file!

        private void btnEncrypt_Click(object sender, EventArgs e)
        {
            if (textBox1.Text.Trim().Length > 0)
            {
                using (OpenFileDialog ofd = new OpenFileDialog())
                {
                    ofd.Title = "Select Source File to Encrypt";
                    if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                    {
                        using (SaveFileDialog sfd = new SaveFileDialog())
                        {
                            sfd.Title = "Save Encrypted File To";
                            if (sfd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                            {
                                if (ofd.FileName != sfd.FileName)
                                {
                                    try
                                    {
                                        EncryptFile(ofd.FileName, sfd.FileName, textBox1.Text);
                                        MessageBox.Show("Done Encrypting File!");
                                    }
                                    catch (Exception ex)
                                    {
                                        MessageBox.Show(ex.ToString(), "Error Encrypting File", MessageBoxButtons.OK, MessageBoxIcon.Error);
                                    }
                                }
                                else
                                {
                                    MessageBox.Show("Source and Target File cannot be the same!");
                                }
                            }
                        }
                    }
                }
            }
            else
            {
                MessageBox.Show("Please enter a Key!");
            }
        }

        private void btnDecrypt_Click(object sender, EventArgs e)
        {
            if (textBox1.Text.Trim().Length > 0)
            {
                using (OpenFileDialog ofd = new OpenFileDialog())
                {
                    ofd.Title = "Select Source File to Decrypt";
                    if (ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                    {
                        using (SaveFileDialog sfd = new SaveFileDialog())
                        {
                            sfd.Title = "Save Decrypted File To";
                            if (sfd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                            {
                                if (ofd.FileName != sfd.FileName)
                                {
                                    try
                                    {
                                        DecryptFile(ofd.FileName, sfd.FileName, textBox1.Text);
                                        MessageBox.Show("Done Decrypting File!");
                                    }
                                    catch (System.Security.Cryptography.CryptographicException cryptoEx)
                                    {
                                        MessageBox.Show(cryptoEx.ToString(), "Invalid Key");
                                    }
                                    catch (Exception ex)
                                    {
                                        MessageBox.Show(ex.ToString(), "Error Reading or Writing File", MessageBoxButtons.OK, MessageBoxIcon.Error);
                                    }
                                }
                                else
                                {
                                    MessageBox.Show("Source and Target File cannot be the same!");
                                }
                            }
                        }
                    }
                }
            }
            else
            {
                MessageBox.Show("Please enter a Key!");
            }
        }

        private void EncryptFile(string sourceFile, string targetFile, string key)
        {
            AesManaged AES = new AesManaged();
            using (MD5CryptoServiceProvider MD5 = new MD5CryptoServiceProvider())
            {
                AES.KeySize = MD5.HashSize; // they are 128 bit compatible
                AES.BlockSize = MD5.HashSize; // they are 128 bit compatible
                AES.IV = MD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(_IV));
                AES.Key = MD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(key));
            }
            using (FileStream reader = new FileStream(sourceFile, FileMode.Open, FileAccess.Read))
            {
                using (FileStream writer = new FileStream(targetFile, FileMode.OpenOrCreate, FileAccess.Write))
                {
                    using (CryptoStream cs = new CryptoStream(writer, AES.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        int bufferSize = 4096;
                        byte[] buffer = new byte[bufferSize];
                        int bytesRead;
                        do
                        {
                            bytesRead = reader.Read(buffer, 0, bufferSize);
                            if (bytesRead != 0)
                            {
                                cs.Write(buffer, 0, bytesRead);
                            }
                        } 
                        while (bytesRead != 0);
                        cs.FlushFinalBlock(); 
                    }
                }
            }
        }

        private void DecryptFile(string sourceFile, string targetFile, string key)
        {
            AesManaged AES = new AesManaged();
            using (MD5CryptoServiceProvider MD5 = new MD5CryptoServiceProvider())
            {
                AES.KeySize = MD5.HashSize; // they are 128 bit compatible
                AES.BlockSize = MD5.HashSize; // they are 128 bit compatible
                AES.IV = MD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(_IV));
                AES.Key = MD5.ComputeHash(ASCIIEncoding.ASCII.GetBytes(key));
            }
            using (FileStream reader = new FileStream(sourceFile, FileMode.Open, FileAccess.Read))
            {
                using (FileStream writer = new FileStream(targetFile, FileMode.OpenOrCreate, FileAccess.Write))
                {
                    using (CryptoStream cs = new CryptoStream(reader, AES.CreateDecryptor(), CryptoStreamMode.Read))
                    {
                        int bufferSize = 4096;
                        byte[] buffer = new byte[bufferSize];
                        int bytesRead;
                        do
                        {
                            bytesRead = cs.Read(buffer, 0, bufferSize);
                            if (bytesRead != 0)
                            {
                                writer.Write(buffer, 0, bytesRead);
                            }
                        }
                        while (bytesRead != 0);
                    }
                }
            }
        }

    }

}

Open in new window

0
 

Author Closing Comment

by:tknayak123
ID: 35210462
This is the exact code I was looking for.

Thanks
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Ransomware is a growing menace to anyone using a computer or mobile device. Here are answers to some common questions about this vicious new form of malware.
The conference as a whole was very interesting, although if one has to make a choice between this one and some others, you may want to check out the others.  This conference is aimed mainly at government agencies.  So it addresses the various compli…
With Secure Portal Encryption, the recipient is sent a link to their email address directing them to the email laundry delivery page. From there, the recipient will be required to enter a user name and password to enter the page. Once the recipient …
The Email Laundry PDF encryption service allows companies to send confidential encrypted  emails to anybody. The PDF document can also contain attachments that are embedded in the encrypted PDF. The password is randomly generated by The Email Laundr…
Suggested Courses
Course of the Month8 days, 11 hours left to enroll

621 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question