Hi guys! I am a newbie in VB.NET and am trying to create a cipher. In my program, before you can decrypt a string, you are prompted to enter a key. After you enter the correct c key,the string is decrypted. The problem is that the plaintext appears at the same time with the key form.The key should be entered first and verified then the plaintext to appear later. I have the following objects on my form;
Set the Visible to false for the plain text. Then, when the entered key is OK. set the property to true.
Hope this helps
Heres another example
If i remember the encrypt and decrypt function were pretty much a cut and paste from the MSDN Library
Imports System.Security.Cryptography
Imports System.Text
Imports System.IO
Public Class Form1
Private Sub btnEncrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEncrypt.Click
Dim key As String = InputBox("Key:", "Encryption Key")
If String.IsNullOrEmpty(key) Then
MsgBox("Key is not optional", MsgBoxStyle.OkOnly, "Encryption Key")
Exit Sub
End If
txtEncrypt.Text = Encrypt(txtPlain.Text, key)
txtPlain.Text = String.Empty
End Sub
Private Sub btnDecrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDecrypt.Click
Dim key As String = InputBox("Key:", "Decryption Key")
If String.IsNullOrEmpty(key) Then
MsgBox("Key is not optional", MsgBoxStyle.OkOnly, "Decryption Key")
Exit Sub
End If
txtPlain.Text = Decrypt(txtEncrypt.Text, key)
txtEncrypt.Text = String.Empty
End Sub
Private Function GetKeys(ByVal KeyString As String, ByVal length As Integer) As Byte()
'Returns a hash value of the secret key
Dim HashValue() As Byte
Dim UE As New UnicodeEncoding()
'Convert the string into an array of bytes.
Dim MessageBytes As Byte() = UE.GetBytes(KeyString)
'Create the hash value from the array of bytes.
Dim SHhash As New SHA1Managed()
HashValue = SHhash.ComputeHash(MessageBytes)
'Optional feature to adjust the length of the hash
ReDim Preserve HashValue(length - 1)
UE = Nothing
SHhash = Nothing
Return HashValue
End Function
Private Function Encrypt(ByVal ClearText As String, ByVal SecretKey As String) As String
Dim EncryptedText As String = String.Empty
Dim mstream As New MemoryStream()
Dim CryptStream As CryptoStream = Nothing
Try
'Get the bytes
Dim plaintextBytes() As Byte = System.Text.Encoding.Unicode.GetBytes(ClearText)
'Create a new instance of the RijndaelManaged class
Dim RMCrypto As New RijndaelManaged()
'get the key and iv
Dim Key As Byte() = GetKeys(SecretKey, 16)
Dim IV As Byte() = GetKeys(SecretKey, 16)
CryptStream = New CryptoStream(mstream, RMCrypto.CreateEncryptor(Key, IV), CryptoStreamMode.Write)
'Encrypt the text
CryptStream.Write(plaintextBytes, 0, plaintextBytes.Length)
CryptStream.FlushFinalBlock()
'Convert the encrypted bytes to a 64 base string
EncryptedText = System.Convert.ToBase64String(mstream.ToArray)
Catch ex As Exception
Finally
CryptStream.Dispose()
mstream.Close()
End Try
Return EncryptedText
End Function
Private Function Decrypt(ByVal EncryptedText As String, ByVal SecretKey As String) As String
Dim PlainText As String = String.Empty
'convert the 64 base string back to bytes
Dim EncryptedBytes() As Byte = System.Convert.FromBase64String(EncryptedText)
Dim mStream As New MemoryStream
Try
Dim RMCrypto As New RijndaelManaged()
'get the key and iv
Dim Key As Byte() = GetKeys(SecretKey, 16)
Dim IV As Byte() = GetKeys(SecretKey, 16)
Dim CryptStream As New CryptoStream(mStream, RMCrypto.CreateDecryptor(Key, IV), CryptoStreamMode.Write)
'Decrypt the message
CryptStream.Write(EncryptedBytes, 0, EncryptedBytes.Length)
CryptStream.FlushFinalBlock()
'Convert the bytes to the plain text
PlainText = System.Text.Encoding.Unicode.GetString(mStream.ToArray)
CryptStream.Close()
mStream.Close()
Catch ex As Exception
MsgBox("The key may be incorrect", MsgBoxStyle.OkOnly, "Decryptoin Error")
Finally
mStream.Dispose()
End Try
Return PlainText
End Function
End ClassGood example on cypheing.
If I understood well your example, you first enter the plain text, then ask for the key in the btnEncrypt_Click event handler, but IMO the question from Denni_Mwebia is how to force the user to enter the key before entering the txtEncrypt.Text. I am wrong?
I not sure what the question is.
The plain text is showing at the same time as the key form? The key should be entered first and verified before decrypting?
If the plain text is showing before the key is entered then it wasn't encrypted in the first place.
I provided an example where you can type in some clear text, hit a button that asks you for a key, encrypts it with the key, removes the clear text and displays the encrypted text. To decrypt it: a button has to be pressed, the original key entered, text is decrypted, and the clear text is displayed.
Thanks to clarify
Thanks guys for your help. I've changed the program to accomodate an easier way of key entry. This is what i've done: below each button i.e Encryption and decryption, i've inserted a textbox, each requiring a key entry. Without the key entry, you cannot proceed any further! Appealing?
So I think the problem is solved.
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