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VB.Net Encrypted Key Generation

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I want to generate 8 byte key using CBC MAC by applying encryption to whole message in vb.net.My code is:

//Main form Code
Imports System.Security .Cryptography
Dim plainText As String
Dim cipherText As String

Dim passPhrase As String
Dim saltValue As String
Dim hashAlgorithm As String
Dim passwordIterati ons As Integer
Dim initVector As String
Dim keySize As Integer

plainText = "Hello, World! how are you, 546548732424 jhsda237 ............... ...624 ASCII charaters"
passPhrase = "Pas5pr@se" ' can be any string
saltValue = "s@1tValue" ' can be any string
hashAlgorithm = "SHA1" ' can be "MD5"
passwordIterati ons = 2 ' can be any number
initVector = "@1B2c3D4e5F6g7 H8" ' must be 16 bytes
keySize = 256 ' can be 192 or 128

cipherText = Module1.Encrypt (plainText, passPhrase, saltValue, hashAlgorithm, passwordIterati ons, initVector, keySize)
MsgBox(String.F ormat("Encrypte d : {0}", cipherText))


//Module code
Imports System
Imports System.IO
Imports System.Text
Imports System.Security .Cryptography

Module Module1
Public Function Encrypt(ByVal plainText As String, ByVal passPhrase As String, ByVal saltValue As String, ByVal hashAlgorithm As String, ByVal passwordIterati ons As Integer, ByVal initVector As String, ByVal keySize As Integer) As String

' Convert strings into byte arrays.
' Let us assume that strings only contain ASCII codes.
' If strings include Unicode characters, use Unicode, UTF7, or UTF8
' encoding.
Dim initVectorBytes As Byte()
initVectorBytes = Encoding.ASCII. GetBytes(initVe ctor)

Dim saltValueBytes As Byte()
saltValueBytes = Encoding.ASCII. GetBytes(saltVa lue)

' Convert our plaintext into a byte array.
' Let us assume that plaintext contains UTF8-encoded characters.
Dim plainTextBytes As Byte()
plainTextBytes = Encoding.UTF8.G etBytes(plainTe xt)

' First, we must create a password, from which the key will be derived.
' This password will be generated from the specified passphrase and
' salt value. The password will be created using the specified hash
' algorithm. Password creation can be done in several iterations.
Dim password As PasswordDeriveB ytes
password = New PasswordDeriveB ytes(passPhrase , _
saltValueBytes, _
hashAlgorithm, _
passwordIterati ons)

' Use the password to generate pseudo-random bytes for the encryption
' key. Specify the size of the key in bytes (instead of bits).
Dim keyBytes As Byte()
keyBytes = password.GetByt es(keySize / 32)

' Create uninitialized Rijndael encryption object.
Dim symmetricKey As RijndaelManaged
symmetricKey = New RijndaelManaged

' It is reasonable to set encryption mode to Cipher Block Chaining
' (CBC). Use default options for other symmetric key parameters.
symmetricKey.Mo de = CipherMode.CBC

' Generate encryptor from the existing key bytes and initialization
' vector. Key size will be defined based on the number of the key
' bytes.
Dim encryptor As ICryptoTransfor m
encryptor = symmetricKey.Cr eateEncryptor(k eyBytes, initVectorBytes )

' Define memory stream which will be used to hold encrypted data.
Dim memoryStream As MemoryStream
memoryStream = New MemoryStream

' Define cryptographic stream (always use Write mode for encryption).
Dim cryptoStream As CryptoStream
cryptoStream = New CryptoStream(me moryStream, _
encryptor, _
CryptoStreamMod e.Write)
' Start encrypting.
cryptoStream.Wr ite(plainTextBy tes, 0, plainTextBytes. Length)

' Finish encrypting.
cryptoStream.Fl ushFinalBlock()

' Convert our encrypted data from a memory stream into a byte array.
Dim cipherTextBytes As Byte()
cipherTextBytes = memoryStream.To Array()

' Close both streams.
memoryStream.Cl ose()
cryptoStream.Cl ose()

' Convert encrypted data into a base64-encoded string.
Dim cipherText As String
cipherText = Convert.ToBase6 4String(cipherT extBytes)

' Return encrypted string.
Encrypt = cipherText
End Function
End Module

Problem is i want to generate 8 byte key on applying CBC MAC to the plain text but it gives the encrypted output of same length as that of plain text.any body know this?
May 28 '07 #1
0 1925

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