Generate Key using Cipher Block Chaining MAC

[danishce]

I have studied that DES CBC algorithm generate 64 bits (8 byte Hex) encrypted output but when i implement the algorithm in vb.net it gives the same length output as my plain text.i need help on how i obtain 8 byte encrypted output.

Private key() As Byte = {1, 2, 3, 4, 5, 6, 7, 8}
Private iv() As Byte = {65, 110, 68, 26, 69, 178, 200, 219}

Dim plainText As String
plainText = "HelloWorldhjsl kajldalkdjlaksj dlakdja"
Dim DES As New System.Security .Cryptography.D ESCryptoService Provider
' Set the cipher mode.
DES.Mode = System.Security .Cryptography.C ipherMode.CBC
' Create the encryptor.
Dim DESEncrypt As System.Security .Cryptography.I CryptoTransform = DES.CreateEncry ptor(Me.key, Me.iv)
' Get a byte array of the string.
Dim Buffer As Byte() = System.Text.ASC IIEncoding.ASCI I.GetBytes(plai nText)
' Transform and return the string.
Dim keyout As String
keyout = Convert.ToBase6 4String(DESEncr ypt.TransformFi nalBlock(Buffer , 0, Buffer.Length))

[RedSon]

I have studied that DES CBC algorithm generate 64 bits (8 byte Hex) encrypted output but when i implement the algorithm in vb.net it gives the same length output as my plain text.i need help on how i obtain 8 byte encrypted output.

Private key() As Byte = {1, 2, 3, 4, 5, 6, 7, 8}
Private iv() As Byte = {65, 110, 68, 26, 69, 178, 200, 219}

Dim plainText As String
plainText = "HelloWorldhjsl kajldalkdjlaksj dlakdja"
Dim DES As New System.Security .Cryptography.D ESCryptoService Provider
' Set the cipher mode.
DES.Mode = System.Security .Cryptography.C ipherMode.CBC
' Create the encryptor.
Dim DESEncrypt As System.Security .Cryptography.I CryptoTransform = DES.CreateEncry ptor(Me.key, Me.iv)
' Get a byte array of the string.
Dim Buffer As Byte() = System.Text.ASC IIEncoding.ASCI I.GetBytes(plai nText)
' Transform and return the string.
Dim keyout As String
keyout = Convert.ToBase6 4String(DESEncr ypt.TransformFi nalBlock(Buffer , 0, Buffer.Length))

I might be missing something but I do not see a call to ComputeHash().

[danishce]

ComputeHash function is available in MD5CryptoServic eProvider Class but in DESCryptoServic eProvider Class ComputeHash is not available instead it will provide ICryptoTransfor m function which uses CreateEncryptor method.

I studied that DES provide 8 byte output key but unable to generate the output key in 8 byte.waiting for any help?

[pbmods]

I have studied that DES CBC algorithm generate 64 bits (8 byte Hex) encrypted output but when i implement the algorithm in vb.net it gives the same length output as my plain text.i need help on how i obtain 8 byte encrypted output.

Private key() As Byte = {1, 2, 3, 4, 5, 6, 7, 8}
Private iv() As Byte = {65, 110, 68, 26, 69, 178, 200, 219}

Dim plainText As String
plainText = "HelloWorldhjsl kajldalkdjlaksj dlakdja"
Dim DES As New System.Security .Cryptography.D ESCryptoService Provider
' Set the cipher mode.
DES.Mode = System.Security .Cryptography.C ipherMode.CBC
' Create the encryptor.
Dim DESEncrypt As System.Security .Cryptography.I CryptoTransform = DES.CreateEncry ptor(Me.key, Me.iv)
' Get a byte array of the string.
Dim Buffer As Byte() = System.Text.ASC IIEncoding.ASCI I.GetBytes(plai nText)
' Transform and return the string.
Dim keyout As String
keyout = Convert.ToBase6 4String(DESEncr ypt.TransformFi nalBlock(Buffer , 0, Buffer.Length))

What does this output? Give us an example.
What were you expecting? Give us an example.

[Banfa]

You might also consider telling us why you want to do this. You keep telling us what you want to do, the why often helps understand the problem too.

[danishce]

Basically i am developing a message interface document and send/receive data to server from my application using winsock TCP/IP. There is a MAC field in the document which apply CBC MAC encryption to plain text that i send to server and return 8 byte key in output.Then i send this 8 byte key with my plain text and the server check my message with their interface. At the server end their is a third party involved which developed server interface so they check my message and gives reply to me either transaction is OK/CANCEL.
When i am using TripleDES it generate 8 byte MAC Key but i want to generate CBC MAC key using DES.The code for TripleDES key is:
dim plaintext as string
plainText = "46546544798752 123449879843132 187984132146546 4"
Dim data As Byte() = ASCIIEncoding.A SCII.GetBytes(p lainText)
Dim mac3des As New MACTripleDES
Dim result As Byte() = mac3des.Compute Hash(data)
output=(result= 52637299) 8 byte

Code for DES key is:
'Dim DES As New DESCryptoServic eProvider
'' Set the cipher mode.
'DES.Mode = CipherMode.CBC
'Dim data As Byte() = ASCIIEncoding.A SCII.GetBytes(p lainText)
'If key Is Nothing Then
' DES.GenerateKey ()
' DES.GenerateIV( )
' key = DES.Key
' iv = DES.IV
'Else
' DES.Key = key
' DES.IV = iv
'End If

'Dim DESEncrypt As ICryptoTransfor m = DES.CreateEncry ptor()
'Dim ms As New MemoryStream
'Dim cs As CryptoStream = New CryptoStream(ms , DESEncrypt, CryptoStreamMod e.Write)
'cs.Write(data, 0, data.Length)
'cs.FlushFinalB lock()
'ms.Position = 0
'Dim result(ms.Lengt h - 1) As Byte
'ms.Read(result , 0, ms.Length)
'cs.Close()
'Dim keyout As Byte()
'keyout = result
output=same length as plain text,i want keyout should be 8 byte.
I hope you understand this.