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Making TripleDES Simple in Visual Basic .NET

, 17 Mar 2006
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This is a simple wrapper class that provides an easy interface for encrypting and decrypting byte arrays and strings.

Introduction

There are many, many examples of how to do encryption and decryption in .NET. So why one more? Well, for one thing, I find that the majority of good code examples of any type are issued in C#. This isn't surprising, since those from a C++ or Java background will have an easier transition to C# than a similarly experienced Visual Basic developer moving to VB.NET. It will take time for the VB.NET community to develop into what the C++ and Java community already has at its disposal. So, I thought that a solid, simple VB.NET example would do well.

Overview

This code example does four things that I think are missing from the examples that I have seen so far:

  • It's written in Visual Basic .NET. Not that it is in any way superior or inferior to C#, but most of the other examples (and all of the good ones) were done in C#.
  • It uses the UTF-8 encoder to ensure that the strings which are encrypted or decrypted are in an 8-bit format. Many examples that I see use the ASCII encoding, which is a 7-bit format. When you combine this with TripleDES (which uses 3, 8-bit blocks for the key), you can get yourself into situations where you cannot decrypt something you encrypted.
  • It uses the Convert object's Base-64 methods to make sure that the encrypted text is output in such a way that it can be easily stored in text files and/or database fields without the risk of your encrypted content being inadvertently modified by implicit conversions.
  • It centralizes the actual encryption and decryption functionality into a single method, thus eliminating what would otherwise be 99% redundant code.

The Code

The complete cTripleDES class in VB.NET:

Imports System.IO
Imports System.Text
Imports System.Security.Cryptography

Friend Class cTripleDES

    ' define the triple des provider
    Private m_des As New TripleDESCryptoServiceProvider

    ' define the string handler
    Private m_utf8 As New UTF8Encoding

    ' define the local property arrays
    Private m_key() As Byte
    Private m_iv() As Byte

    Public Sub New(ByVal key() As Byte, ByVal iv() As Byte)
        Me.m_key = key
        Me.m_iv = iv
    End Sub

    Public Function Encrypt(ByVal input() As Byte) As Byte()
        Return Transform(input, m_des.CreateEncryptor(m_key, m_iv))
    End Function

    Public Function Decrypt(ByVal input() As Byte) As Byte()
        Return Transform(input, m_des.CreateDecryptor(m_key, m_iv))
    End Function

    Public Function Encrypt(ByVal text As String) As String
        Dim input() As Byte = m_utf8.GetBytes(text)
        Dim output() As Byte = Transform(input, _
                        m_des.CreateEncryptor(m_key, m_iv))
        Return Convert.ToBase64String(output)
    End Function

    Public Function Decrypt(ByVal text As String) As String
        Dim input() As Byte = Convert.FromBase64String(text)
        Dim output() As Byte = Transform(input, _
                         m_des.CreateDecryptor(m_key, m_iv))
        Return m_utf8.GetString(output)
    End Function

    Private Function Transform(ByVal input() As Byte, _
        ByVal CryptoTransform As ICryptoTransform) As Byte()
        ' create the necessary streams
        Dim memStream As MemoryStream = New MemoryStream
        Dim cryptStream As CryptoStream = New _
            CryptoStream(memStream, CryptoTransform, _
            CryptoStreamMode.Write)
        ' transform the bytes as requested
        cryptStream.Write(input, 0, input.Length)
        cryptStream.FlushFinalBlock()
        ' Read the memory stream and convert it back into byte array
        memStream.Position = 0
        Dim result(CType(memStream.Length - 1, System.Int32)) As Byte
        memStream.Read(result, 0, CType(result.Length, System.Int32))
        ' close and release the streams
        memStream.Close()
        cryptStream.Close()
        ' hand back the encrypted buffer
        Return result
    End Function

End Class

The complete cTripleDES class in C#:

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

namespace Utilities.Crypto
{
    class cTripleDES
    {
        // define the triple des provider
        private TripleDESCryptoServiceProvider m_des = 
                 new TripleDESCryptoServiceProvider();

        // define the string handler
        private UTF8Encoding m_utf8 = new UTF8Encoding();

        // define the local property arrays
        private byte[] m_key;
        private byte[] m_iv;

        public cTripleDES(byte[] key, byte[] iv)
        {
            this.m_key = key;
            this.m_iv = iv;
        }

        public byte[] Encrypt(byte[] input)
        {
            return Transform(input, 
                   m_des.CreateEncryptor(m_key, m_iv));
        }

        public byte[] Decrypt(byte[] input)
        {
            return Transform(input, 
                   m_des.CreateDecryptor(m_key, m_iv));
        }

        public string Encrypt(string text)
        {
            byte[] input = m_utf8.GetBytes(text);
            byte[] output = Transform(input, 
                            m_des.CreateEncryptor(m_key, m_iv));
            return Convert.ToBase64String(output);
        }

        public string Decrypt(string text)
        {
            byte[] input = Convert.FromBase64String(text);
            byte[] output = Transform(input, 
                            m_des.CreateDecryptor(m_key, m_iv));
            return m_utf8.GetString(output);
        }

        private byte[] Transform(byte[] input, 
                       ICryptoTransform CryptoTransform)
        {
            // create the necessary streams
            MemoryStream memStream = new MemoryStream();
            CryptoStream cryptStream = new CryptoStream(memStream, 
                         CryptoTransform, CryptoStreamMode.Write);
            // transform the bytes as requested
            cryptStream.Write(input, 0, input.Length);
            cryptStream.FlushFinalBlock();
            // Read the memory stream and
            // convert it back into byte array
            memStream.Position = 0;
            byte[] result = memStream.ToArray();
            // close and release the streams
            memStream.Close();
            cryptStream.Close();
            // hand back the encrypted buffer
            return result;
        }
    }
} 

Using the cTripleDES class in VB.NET:

' define the local key and vector byte arrays
Private ReadOnly key() As Byte = _
  {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, _
  15, 16, 17, 18, 19, 20, 21, 22, 23, 24}
Private ReadOnly iv() As Byte = {8, 7, 6, 5, 4, 3, 2, 1}

' instantiate the class with the arrays
Private des As New cTripleDES(key, iv)

' for the example, define a variable with the encrypted value
Private ReadOnly encryptedData As String = "++XIiGymvbg="

' now, decrypt the data
Private decryptedData As String = des.Decrypt(encryptedData)

' the value of decryptedData should be "test",
' but for our example purposes, let's re-encrypt it
Private newEncryptedData As String = des.Encrypt(decryptedData)

Using the cTripleDES class in C#:

// define the local key and vector byte arrays
byte[] key = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 
              13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24};
byte[] iv = {8, 7, 6, 5, 4, 3, 2, 1};

// instantiate the class with the arrays
cTripleDES des = new cTripleDES(key, iv);

// for the example, define a variable with the encrypted value
string encryptedData = "++XIiGymvbg=";

// now, decrypt the data
string decryptedData = des.Decrypt(encryptedData);

// the value of decryptedData should be "test",
// but for our example purposes, let's re-encrypt it
string newEncryptedData = des.Encrypt(decryptedData);

Conclusion

Hopefully, this simple, straight-forward example shows how to effectively and efficiently wrap the TripleDES (or any other encryption) functionality in Visual Basic .NET syntax. Of course, the same principles can just as easily be applied to a C#, J#, or managed C++ implementation.

Update (March 17, 2005)

It's been nearly two years since I first published this article and it's gotten a fair number of views, votes, and thanks. I'd like to thank you all for your kindness and, in return, I have updated the article with the much asked-for C# version of the class. Happy coding!

License

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About the Author

Tony Selke
Architect Wyvern Software
United States United States
Tony Selke is an independant consultant who has spent the last 20 years working with Microsoft technologies (VB, VC++, ASP, J++, C#, VB.NET, SQL Server, etc.) to develop solutions used in all kinds of market verticals (industrial, pharmaceutical, financial, marketing, multimedia, educational, telecommunications, etc.). He obtained his first MCSD certification in 1998 and his second in 2004, with an MCDBA in 2005. In addition, he has taught courses for MCSD certification students as well as programming classes at Penn State University.

Comments and Discussions

 
Question2 different key can decrypt data [modified] Pinmemberturkert24-Jan-13 22:41 
GeneralMy vote of 5 PinmemberRichard Osafo2-Jun-12 9:07 
QuestionNo good dead goes unpunished??? PinmemberTom Hawkins20-Sep-11 10:55 
AnswerRe: No good dead goes unpunished??? PinmemberTony Selke21-Sep-11 2:41 
GeneralRe: No good dead goes unpunished??? PinmemberTom Hawkins22-Sep-11 9:34 
GeneralSimplified Transform() Function Pinmemberpeterhar122-May-11 5:57 
AnswerRe: Simplified Transform() Function PinmemberTony Selke22-May-11 6:49 
GeneralMy vote of 5 PinmemberMichael Rawi30-Mar-11 19:03 
QuestionDo you need to setup IDisposable (Dispose Pattern) in your class? and how? Pinmemberdanvmn4-Feb-11 7:35 
AnswerRe: Do you need to setup IDisposable (Dispose Pattern) in your class? and how? PinmemberTony Selke4-Feb-11 7:55 
GeneralRe: Do you need to setup IDisposable (Dispose Pattern) in your class? and how? Pinmemberdanvmn4-Feb-11 8:27 
GeneralBad encrypt decrypt Pinmemberonkie breed25-Dec-10 13:15 
AnswerRe: Bad encrypt decrypt [modified] PinmemberTony Selke4-Feb-11 8:13 
GeneralRe: Bad encrypt decrypt Pinmemberdanvmn4-Feb-11 8:35 
AnswerRe: Bad encrypt decrypt PinmemberTony Selke4-Feb-11 8:39 
GeneralRe: Bad encrypt decrypt Pinmemberdanvmn7-Feb-11 8:29 
QuestionOne step more PinmemberLadyReader1-Dec-10 6:11 
AnswerRe: One step more PinmemberTony Selke1-Dec-10 6:30 
GeneralRe: One step more PinmemberLadyReader1-Dec-10 8:31 
GeneralTripleDESCryptoServiceProvider PinmemberJim317-Aug-10 8:41 
GeneralRe: TripleDESCryptoServiceProvider PinmemberTony Selke7-Aug-10 8:44 
GeneralEncryption on windows mobile device using the compact framework.... [modified] Pinmemberdmetzgar19-Nov-09 7:26 
AnswerRe: Encryption on windows mobile device using the compact framework.... PinmemberTony Selke19-Nov-09 7:46 
GeneralRe: Encryption on windows mobile device using the compact framework.... Pinmemberdmetzgar19-Nov-09 7:48 
JokeRe: Encryption on windows mobile device using the compact framework.... PinmemberTony Selke19-Nov-09 7:53 
GeneralRe: Encryption on windows mobile device using the compact framework.... Pinmemberdmetzgar20-Nov-09 10:27 
GeneralMy vote of 1 PinmemberMircea Sirghi29-Jul-09 4:11 
RantRe: [Your] vote of 1 PinmemberTony Selke20-Aug-09 7:20 
GeneralThank you Pinmembercherishnews2-Dec-08 22:42 
GeneralRe: Thank you Pinmembermoonshaddow15-Jul-09 16:34 
GeneralEncrypted result is not same in java and this .NET class Pinmemberqurban ali25-Nov-08 4:54 
QuestionAlready have key...now what? PinmemberMCSD-Gandalf30-Jul-08 6:37 
AnswerRe: Already have key...now what? PinmemberTony Selke31-Jul-08 3:44 
QuestionThe encryption key arrays Pinmemberscottpurcell16-Jun-08 6:27 
AnswerRe: The encryption key arrays PinmemberTony Selke16-Jun-08 6:43 
GeneralRe: The encryption key arrays Pinmemberscottpurcell16-Jun-08 8:59 
AnswerRe: The encryption key arrays PinmemberTony Selke16-Jun-08 9:03 
QuestionHow to use PL/SQL to decrypt the value PinmemberMattinTally29-May-08 6:12 
GeneralCheck this example out, triple des appears to be broken in .NET 1.0: PinmemberJacmac7-May-08 11:53 
RantRe: Check this example out, triple des appears to be broken in .NET 1.0: PinmemberTony Selke7-May-08 12:56 
QuestionWorks with a good key, but what about a bad key? PinmemberJacmac1-May-08 13:01 
AnswerRe: Works with a good key, but what about a bad key? PinmemberJacmac1-May-08 13:39 
AnswerRe: Works with a good key, but what about a bad key? PinmemberTony Selke1-May-08 15:02 
GeneralRe: Works with a good key, but what about a bad key? PinmemberJacmac5-May-08 13:32 
GeneralGetting this code to work on Compact.NET Pinmembervbshaman16-Feb-08 14:44 
GeneralSubject goes here [modified] PinmemberAliasGoesHere24-Oct-07 11:17 
AnswerRe: Subject goes here PinmemberTony Selke25-Oct-07 4:12 
QuestionRunning order Pinmemberbarneyswedge17-Oct-07 6:02 
AnswerRe: Running order PinmemberTony Selke17-Oct-07 6:08 
GeneralOne other related encryption article in CodeProject ... PinmemberNathan Blomquist27-Sep-07 16:31 

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