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System.Security.Cryptography Namespace in VB.NET

Posted by Dinesh Beniwal in Articles | Visual Basic Language on September 13, 2010

Tags: Namespace, NETSystem.Security.Cryptography Namespace in VB.NET, System.Security.Cryptography

In this article I will explain you about System.Security.Cryptography Namespace in VB.NET.

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Reader Level: Beginner

The System.Security.Cryptography namespace contains support for the most common symmetric (DES, 3DES, RC2, Rijndael), asymmetric (RSA, DSA), and hash (MD5, SHA-1, SHA-256, SHA- 384, SHA-512) cryptography algorithms. It also includes a helpful class to encrypt and decrypt streams. You can use this class, called CryptoStream, in combination with other stream classes or you can use several CryptoStream class objects together. With a little effort, you can feed the output of one CryptoStream object into another CryptoStream object.

Table 22.6 lists the classes and interfaces that are part of the System.Security.Cryptography namespace of the VB.NET Framework base class library. These classes and interfaces define the abstract object model for encryption algorithms within the VB.NET Framework. New algorithms may be added to the VB.NET Framework by subclassing and/or implementing a portion of these classes and interfaces.

Table 22.6: Classes and Interfaces in the System.Security.Cryptography Namespace

Listing 22.35 illustrates the use of DES and CryptoStream classes to encipher and decipher a file.

Listing 22.35: Cryptostream1.VB, CryptoStream with DES

Imports System.IO
Imports System.Security
Imports System.Security.Cryptography
Imports System.Text
Class CryptoDESSample
     Shared Sub Main(ByVal args As String())
         Dim fsInput As New FileStream("c:\myfile.txt", FileMode.Open, FileAccess.Read)
         Dim fsCiphered As New FileStream("c:\ciphered.txt", FileMode.Create, FileAccess.Write
         Dim ourDESProvider As New DESCryptoServiceProvider()
         ' our 8 byte DES secret key is 12345678
         ourDESProvider.Key = ASCIIEncoding.ASCII.GetBytes("12345678")
         ourDESProvider.IV = ASCIIEncoding.ASCII.GetBytes("12345678")
         Dim des1 As ICryptoTransform = ourDESProvider.CreateEncryptor()
         Dim des2 As ICryptoTransform = ourDESProvider.CreateDecryptor()
         Dim cryptostream1 As New CryptoStream(fsCiphered, des1, CryptoStreamMode.Write)
         Dim bytearrayinput As Byte() = New Byte(fsInput.Length - 1) {}
         fsInput.Read(bytearrayinput, 0, bytearrayinput.Length)
         cryptostream1.Write(bytearrayinput, 0, bytearrayinput.Length)
         cryptostream1.Close()
         fsInput.Close()
         fsCiphered.Close()
         Dim fsread As New FileStream("c:\ciphered.txt", FileMode.Open, FileAccess.Read)
         Dim cryptostream2 As New CryptoStream(fsread, des2, CryptoStreamMode.Read)
         Dim fsEnciphered As New StreamWriter("c:\enciphered.txt")
         fsEnciphered.Write(New StreamReader(cryptostream2).ReadToEnd())
         fsEnciphered.Flush()
         fsEnciphered.Close()
     End Sub
End Class

The code in Listing 22.36 uses the SHA1 algorithm to compute the hash value of a given string.

Listing 22.36: Hash1.VB, Hashing a String Using SHA-1 Algorithm

Imports System.IO
Imports System.Security
Imports System.Security.Cryptography
Public Class Class1
     Shared Sub Main(ByVal args As String())
         Dim str1 As [String] = "MCBinc"
         Dim char1a As [Char]() = str1.ToCharArray()
         Dim byte1a As [Byte]() = New [Byte](char1a.Length - 1) {}
         For i As Integer = 0 To byte1a.Length - 1
             byte1a(i) = CType(AscW(char1a(i)), [Byte])
         Next
         ' create hash value from str1 using SHA1 instance
         ' returned by CryptoConfig
         Dim hash1 As Byte() = DirectCast(CryptoConfig.CreateFromName("SHA1"), HashAlgorithm
         .ComputeHash(byte1a)
         ' or you can use directly created instance of the SHA1 class
         ' byte[] hash1 = (new SHA1CryptoServiceProvider()).ComputeHash(byte1a );
         Console.WriteLine(str1 & " hashed Value is <" & BitConverter.ToString(hash1) & ">")
         Console.ReadLine()
     End Sub
End Class

Output Window

Conclusion

Hope this article would have helped you in understanding System.Security.Cryptography Namespace in VB.NET.

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System.Security.Cryptography Namespace in VB.NET

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