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Home » VB.NET » Encryption/Decryption using RSA, DES, 3DES and Rijindael in VS.Net 2005

Encryption/Decryption using RSA, DES, 3DES and Rijindael in VS.Net 2005


This article will give the detailed picture of Encryption/Decryption in .NET. Cryptography is a way to encrypt and decrypt data. By encrypting data you are protecting your data from other curious users who would like to know the data that is present.

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The System.Security.Cryptographic namespace within the Microsoft .NET Framework provides a variety of tools to aid in encryption and decryption. The CryptoStream class is used in sample to demonstrate the encryption and decryption with System.Security.Cryptographic.SymmetricAlgorithm, such as DESCryptoServiceProvider, RC2CryptoServiceProvider, and RijndaelManaged classes.

A conventional encryption scheme has five major parts:

  • Ciphertext - This is the encrypted or scrambled message produced by applying the algorithm to the plaintext message using the secret key.

  • Plaintext - This is the text message to which an algorithm is applied.

  • Secret Key - This is the input for the algorithm as the key dictates the encrypted outcome.

  • Encryption Algorithm - It performs mathematical operations to conduct substitutions and transformations to the plaintext.

  • Decryption Algorithm - This is the encryption algorithm in reverse. It uses the ciphertext, and the secret key to derive the plaintext message.

Types of Cryptography.

 

The following are the different types of cryptographic primitives that are used in .Net to encrypt and decrypt data.

  • Private-key encryption or Symmetric Cryptography
  • Public-key encryption or Asymmetric Cryptography.
  • Cryptographic Signing.
  • Cryptographic hashes.

Private key Encryption.

 

Private Key encryption, also referred to as conventional or symmetric or single-key encryption was the only available option prior to the advent of Public Key encryption. This key requires all communicating parties, to share a common key. With private-key encryption, you encrypt a secret message using a key that only you know. To decrypt the message, you need to use the same key. Private-key cryptography is effective only if the key can be kept secret. Despite the potential weakness of private-key encryption, it is very easy to implement and computationally doesn't consume excessive resources.

 

Public-key Encryption.

 

Public key encryption algorithms are based on the premise that each sender and recipient has a private key, known only to him/her and a public key, which can be known by anyone. Each encryption/decryption process requires at least one public key and one private key. Each is related to the other mathematically, such that messages encrypted with the public key can only be decrypted with the corresponding private key.

 

'This function creates an object of TDES Class and uses the ENCRYPT method to actually encrypt your

'string in a required format.

'parameter to be send to this method is the string which is to be encrypted and the Encrypt Type

Private Function encryptText(ByVal text As String, ByVal encType As String)

Try

Dim utf8encoder As UTF8Encoding = New UTF8Encoding

TDES = New TripleDES

txtEnc = TDES.Encrypt(txtEncrypt.Text, encType)

txtData.Text = "Encrypted text: "

For i As Integer = 0 To txtEnc.Length - 1

txtData.AppendText(Chr(txtEnc(i)))

Next

txtData.AppendText(vbNewLine & vbNewLine)

txtData.AppendText("Decrypted Text after encryption: ")

txtData.AppendText(TDES.Decrypt(txtEnc, encType))

txtData.AppendText(vbNewLine & vbNewLine)

txtData.AppendText("Encrypted text length (in bits): " & txtEnc.LongLength.ToString())

Catch ex As Exception

MessageBox.Show(ex.Message)

End Try

End Function

 

Private Sub btnEncrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEncrypt.Click

If (txtEncrypt.Text.Length > 0) Then

txtData.Text = String.Empty

Select Case cmbEncType.Text

Case "RSA"

If (txtPublic.Text.Trim() <> String.Empty And txtPrivate.Text.Trim() <> String.Empty) Then

EncryptRSA(txtEncrypt.Text)

Else

MessageBox.Show("Keys not generated!", "Invalid Keys", MessageBoxButtons.OK, MessageBoxIcon.Error)

End If

Case "DES"

encryptText(txtEncrypt.Text, cmbEncType.Text)

Case "3DES"

encryptText(txtEncrypt.Text, cmbEncType.Text)

Case Else

EncryptRijnDael(txtEncrypt.Text, cmbEncType.Text)

End Select

End If

End Sub

 

Private Sub btnDecrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)

If (txtData.Text.Trim().Length > 0) Then

txtData.Text = String.Empty

decryptText(txtData.Text.Trim())

End If

End Sub

 

'This function creates an object of TDES Class and uses the ENCRYPTRSA method to actually encrypt your string in a RSA format.

Private Function EncryptRSA(ByVal text As String)

Try

Dim key As String

Dim arrlis As ArrayList

TDES = New TripleDES

arrlis = TDES.EncryptRSA(text, txtPublic.Text)

'txtEnc = TDES.EncryptRSA(text)

txtData.Text = "Encrypted text: "

For j As Integer = 0 To arrlis.Count - 1

txtEnc = CType(arrlis(j), Byte())

For i As Integer = 0 To txtEnc.Length - 1

txtData.AppendText(Chr(txtEnc(i)))

Next

Next

txtData.AppendText(vbNewLine & vbNewLine)

txtData.AppendText("Encrypted text length (in bits): " & txtEnc.LongLength.ToString())

txtData.AppendText(vbNewLine & vbNewLine)

txtData.AppendText("Decrypted Text after encryption: ")

For j As Integer = 0 To arrlis.Count - 1

txtEnc = CType(arrlis(j), Byte())

txtEnc = TDES.DecryptRSA(txtEnc, txtPrivate.Text)

For ctr As Integer = 0 To (txtEnc.Length - 1)

txtData.AppendText(Chr(txtEnc(ctr)))

Next ctr

Next 

Catch ex As Exception

MessageBox.Show(ex.Message)

End Try

End Function

 

'This function creates an object of TDES Class and uses the ENCRYPT method to actually encrypt your string in a Rijindael format.

Private Function EncryptRijnDael(ByVal text As String, ByVal encType As String)

Try

TDES = New TripleDES

txtData.Text = "Encrypted string: "

Dim passPhrase As String = ConfigurationSettings.AppSettings("PassPhrase")

Dim saltValue As String = ConfigurationSettings.AppSettings("SaltValue")

Dim iterations As String = ConfigurationSettings.AppSettings("PasswordIterations")

Dim IV As String = ConfigurationSettings.AppSettings("InitVector")

Dim keySize As String = ConfigurationSettings.AppSettings("KeySize")

encType = ConfigurationSettings.AppSettings("EncType")

Dim encString As String = TDES.Encrypt(text, passPhrase, saltValue, encType, iterations, IV, Integer.Parse(keySize))

txtData.AppendText(encString & vbNewLine & vbNewLine)

txtData.AppendText("Decrypted string after encryption: ")

txtData.AppendText(TDES.Decrypt(encString, passPhrase, saltValue, encType, iterations, IV,

Integer.Parse(keySize)))

Catch ex As Exception

MessageBox.Show(ex.Message)

End Try

End Function

 

Private Sub btnEncRSA_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEncRSA.Click

txtData.Text = String.Empty

EncryptRSA(txtEncrypt.Text)

End Sub

 

Private Sub btnClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClose.Click

Close()

End Sub

 

Private Sub cmbEncType_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbEncType.SelectedIndexChanged

Select Case cmbEncType.Text

Case "RSA"

btnGetKey.Visible = True

lblPublic.Visible = True

lblPrivate.Visible = True

txtPublic.Visible = True

txtPrivate.Visible = True

txtPublic.Clear()

txtPrivate.Clear()

Case Else

btnGetKey.Visible = False

lblPublic.Visible = False

lblPrivate.Visible = False

txtPublic.Visible = False

txtPrivate.Visible = False

End Select

End Sub

 

'This function creates your Public Keys and Private Keys using GetKeysForRSA method From TripleDES Class

Private Sub GetKeys()

Try

pubKey = String.Empty

priKey = String.Empty

TDES = New TripleDES

TDES.GetKeysForRSA(pubKey, priKey)

txtData.Clear()

txtData.AppendText("Public Key: " & pubKey & vbNewLine & vbNewLine)

txtData.AppendText("Private Key: " & priKey & vbNewLine & vbNewLine)

txtPublic.Text = pubKey

txtPrivate.Text = priKey

Catch ex As Exception

MessageBox.Show(ex.Message)

End Try

End Sub

 

Private Sub btnGetKey_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGetKey.Click

GetKeys()

End Sub 

Output;-

 

If you run the Sample Application (XMLReader), the output will be as follows:-

 

 

 

 

 

 

 

 

 

 

Conclusion:-

 

After reading this article you will get the good idea of Cryptography, What this terminology means? You can also download a running sample which explains about all (DES, RSA, Rijindael and 3DES) kind of Cryptography mechanism.


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 About the author
 
Sonu Chauhan
Sonu holds B. Sc. (Mathmatics, Physics & Statistics) and MCA (Master's of Computer Applications) degrees. Currently he is working with Merrill Lynch. India and has extensive experience in web technologies using .NET and SQL Reporting services. Sonu also has good hands on experience in Micorosoft Content Management Server.
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 Comments
Encryting and decrypting Query String Variables in asp.net using C# by Mahesh On July 16, 2007
Hi, I need to encrypt the URL having Query string variables when i submit the page. When i click on the URL the encrpted Query string variables should be decrypted. Can u pls help me in this regard.
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Encryting and decrypting Query String Variables in asp.net using C# by Mahesh On July 16, 2007
Hi, I need to encrypt the URL having Query string variables when i submit the page. When i click on the URL the encrpted Query string variables should be decrypted. Can u pls help me in this regard.
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What is up with the Click and see the magic button? by David On December 2, 2008
Why would someone post an application with a comment like this in his program? I found it rather amusing that clicking the button causes the application to crash.
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thank,s by hadri On February 6, 2010
than,ks fery macth
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Thanks . . by Shawn On June 2, 2010
Very informative . .
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