Rijndael managed: plaintext length detction
- by sheepsimulator
I am spending some time learning how to use the RijndaelManaged library in .NET, and developed the following function to test encrypting text with slight modifications from the MSDN library:
Function encryptBytesToBytes_AES(ByVal plainText As Byte(), ByVal Key() As Byte, ByVal IV() As Byte) As Byte()
' Check arguments.
If plainText Is Nothing OrElse plainText.Length <= 0 Then
Throw New ArgumentNullException("plainText")
End If
If Key Is Nothing OrElse Key.Length <= 0 Then
Throw New ArgumentNullException("Key")
End If
If IV Is Nothing OrElse IV.Length <= 0 Then
Throw New ArgumentNullException("IV")
End If
' Declare the RijndaelManaged object
' used to encrypt the data.
Dim aesAlg As RijndaelManaged = Nothing
' Declare the stream used to encrypt to an in memory
' array of bytes.
Dim msEncrypt As MemoryStream = Nothing
Try
' Create a RijndaelManaged object
' with the specified key and IV.
aesAlg = New RijndaelManaged()
aesAlg.BlockSize = 128
aesAlg.KeySize = 128
aesAlg.Mode = CipherMode.ECB
aesAlg.Padding = PaddingMode.None
aesAlg.Key = Key
aesAlg.IV = IV
' Create a decrytor to perform the stream transform.
Dim encryptor As ICryptoTransform = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV)
' Create the streams used for encryption.
msEncrypt = New MemoryStream()
Using csEncrypt As New CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write)
Using swEncrypt As New StreamWriter(csEncrypt)
'Write all data to the stream.
swEncrypt.Write(plainText)
End Using
End Using
Finally
' Clear the RijndaelManaged object.
If Not (aesAlg Is Nothing) Then
aesAlg.Clear()
End If
End Try
' Return the encrypted bytes from the memory stream.
Return msEncrypt.ToArray()
End Function
Here's the actual code I am calling encryptBytesToBytes_AES() with:
Private Sub btnEncrypt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEncrypt.Click
Dim bZeroKey As Byte() = {&H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0, &H0}
PrintBytesToRTF(encryptBytesToBytes_AES(bZeroKey, bZeroKey, bZeroKey))
End Sub
However, I get an exception thrown on swEncrypt.Write(plainText) stating that the 'Length of the data to encrypt is invalid.'
However, I know that the size of my key, iv, and plaintext are 16 bytes == 128 bits == aesAlg.BlockSize. Why is it throwing this exception? Is it because the StreamWriter is trying to make a String (ostensibly with some encoding) and it doesn't like &H0 as a value?
