RSACryptoServiceProvider & Bad Key Exception

Hi,

I'm hoping somebody can help me with this one. I encrypt a simple string with the RSACryptoServiceProvider, export the RSAParameters and then Serialize the exported RSAParameters, together with the encrypted string, to a file using a BinaryFormatter.

Later I deserialize the whole lot, import the RSAParameters into a newly created RSACryptoServiceProvider, and try to decryp the string, but I keep on getting a 'Bad Key' exception.

What am I doing wrong here

I start with this piece of code:

Private Sub mnuToolsSecSettings_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles mnuToolsSecSettings.Click

Dim sec As SecuritySettings

Dim pw As String

Dim epw As String

'Create a Cipher package

Dim cp As CipherPackage

'Check if the file, to which the package had previously been serialized, exists

If IO.File.Exists(QualifyPath(Application.UserAppDataPath) & DataFileName & ".bin") Then

'If it does, deserialize it

cp = CipherStorage.LoadCipherPackage()

If Not (cp Is Nothing) Then

'If the password had previously been encrypted, the exception happens here
pw = CipherEngine.DecryptString(cp)

'Create a new password window, displaying the old password

sec = New SecuritySettings(pw)

Else

'Create a new password window, displaying NO old password

sec = New SecuritySettings

End If

Else

'Create a new password window, displaying NO old password

sec = New SecuritySettings

End If

'Show the password dialog box

If sec.ShowDialog(Me) = DialogResult.OK Then

'Get the new password

pw = sec.txtNewPassword1.Text

'Encrypt the password

cp = CipherEngine.EncryptString(pw)

'Serialize the password and RSAParameters to file

CipherStorage.SaveCipherPackage(cp)

End If

sec.Dispose()

sec = Nothing

cp = Nothing

End Sub

and this is the rest of the code:

Imports System.Runtime.Serialization.Formatters

Imports System.Security.Cryptography

Imports System.IO

Imports System.Text

<Serializable()> _

Class CipherPackage

Public cipherBytes() As Byte ' RC2 encrypted message text

Public params As RSAParameters

End Class 'CipherPackage

Class CipherEngine

Public Shared Function EncryptString(ByVal str As String) As CipherPackage

' Convert string to a byte array

Dim package As New CipherPackage

Dim plainBytes As Byte() = Encoding.ASCII.GetBytes(str)

' Encrypt the Text Message using RSA

Dim rsa As New RSACryptoServiceProvider

package.params = rsa.ExportParameters(True)

package.cipherBytes = rsa.Encrypt(plainBytes, False)

rsa.Clear()

rsa = Nothing

Return package

End Function 'EncryptMessage

Public Shared Function DecryptString(ByVal package As CipherPackage) As String

Dim result As String = String.Empty

If Not (package Is Nothing) Then

Dim rsa As New RSACryptoServiceProvider

rsa.ImportParameters(package.params)

Dim decrypt_result() As Byte = rsa.Decrypt(package.cipherBytes, False)

result = Encoding.ASCII.GetString(decrypt_result)

rsa.Clear()

rsa = Nothing

End If

Return result

End Function 'DecryptMessage

End Class 'Person

Class CipherStorage

Public Shared Sub SaveCipherPackage(ByVal package As CipherPackage)

Try

Dim fs As New IO.FileStream(QualifyPath(Application.UserAppDataPath) & DataFileName & ".bin", IO.FileMode.Create)

Dim formatter As New Binary.BinaryFormatter

formatter.Serialize(fs, package)

formatter = Nothing

fs.Close()

fs = Nothing

Catch e As Exception

Console.WriteLine(e.Message)

End Try

End Sub

Public Shared Function LoadCipherPackage() As CipherPackage

Dim result As CipherPackage

Try

Dim fs As New IO.FileStream(QualifyPath(Application.UserAppDataPath) & DataFileName & ".bin", IO.FileMode.Open)

Dim formatter As New Binary.BinaryFormatter

result = CType(formatter.Deserialize(fs), CipherPackage)

formatter = Nothing

fs.Close()

fs = Nothing

Catch e As Exception

Console.WriteLine(e.Message)

End Try

Return result

End Function

Any help would be appreciated!

Charl

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