Using cryptographic streams with XML

24 Sep 2006 1:30 PM

theinsanecoder

Hi, i'm using the xmlserializer to load and unload data from my files
but i want to crypt them using a not so secure cryptographic encoder.
My code to encrypt "seems" to work fine, the file is outputted but when
i import the file again using the same concept (but in reversed form) i
get XMLDocument is invalid (1, 1) exception thrown back at me. Here is
the code :

SAVING PORTION

                'Save the game
                Dim oXS As XmlSerializer = New
XmlSerializer(GetType(Game.Game))
                Dim oStmW As StreamWriter
                Dim oXmlW As XmlTextWriter

                'Setup the stream writer
                oStmW = New StreamWriter(pFilename)

                'Setup cryptographic stream cypher
                Dim CryptoAlgo As New DESCryptoServiceProvider()
                Dim Cryptographer As
System.Security.Cryptography.CryptoStream
                CryptoAlgo.BlockSize = 64
                CryptoAlgo.KeySize = 64
                Cryptographer = New
System.Security.Cryptography.CryptoStream(oStmW.BaseStream,
CryptoAlgo.CreateEncryptor(KEY_8, IV_8), CryptoStreamMode.Write)

                'Setup the text writer with cryptostream instead of
original stream (Crypto will link them)
                oXmlW = New XmlTextWriter(Cryptographer, New
System.Text.UTF8Encoding())

                'Execute the write
                oXS.Serialize(oXmlW, Game)
                oXmlW.Close()

LOADING PORTION

                'Load the new game
                Dim oXS As XmlSerializer = New
XmlSerializer(GetType(Game.Game))
                Dim oStmR As StreamReader
                Dim oXmlR As XmlTextReader

                'Setup the stream reader
                oStmR = New StreamReader(pFilename)

                'Setup cryptographic stream cypher
                Dim CryptoAlgo As New DESCryptoServiceProvider()
                Dim Cryptographer As
System.Security.Cryptography.CryptoStream
                CryptoAlgo.BlockSize = 64
                CryptoAlgo.KeySize = 64
                Cryptographer = New
System.Security.Cryptography.CryptoStream(oStmR.BaseStream,
CryptoAlgo.CreateEncryptor(KEY_8, IV_8), CryptoStreamMode.Read)

                'Setup the text reader with cryptostream instead of
original stream (Crypto will link them)
                oXmlR = New XmlTextReader(Cryptographer)

                'Execute the read
                oXmlR.WhitespaceHandling =
WhitespaceHandling.Significant
                Game = oXS.Deserialize(oXmlR)
                oXmlR.Close()

Like said earlier, SAVING seems to work fine and outputs a file that is
encrypted when i open it from notepad, but i may be wrong, maybe it's
just outputting rubish. The Load definitely doesn't work throwing back
an InvalidOperationException with the following content, "There is an
error in the XML document (1, 1)"

Can anyone help please?

24 Sep 2006 4:44 PM

tomb

Try not using the xmlwriter for the encrypted output. Just use the
xmlreader for the unencrypted input. Mind you, I'm no expert on xml nor
cryptography, but purely from a logical perspective, the . It's worth a
shot.

Tom

theinsaneco***@gmail.com wrote:

Show quoteHide quote

>Hi, i'm using the xmlserializer to load and unload data from my files
>but i want to crypt them using a not so secure cryptographic encoder.
>My code to encrypt "seems" to work fine, the file is outputted but when
>i import the file again using the same concept (but in reversed form) i
>get XMLDocument is invalid (1, 1) exception thrown back at me. Here is
>the code :
>
>SAVING PORTION
>
>                'Save the game
>                Dim oXS As XmlSerializer = New
>XmlSerializer(GetType(Game.Game))
>                Dim oStmW As StreamWriter
>                Dim oXmlW As XmlTextWriter
>
>                'Setup the stream writer
>                oStmW = New StreamWriter(pFilename)
>
>                'Setup cryptographic stream cypher
>                Dim CryptoAlgo As New DESCryptoServiceProvider()
>                Dim Cryptographer As
>System.Security.Cryptography.CryptoStream
>                CryptoAlgo.BlockSize = 64
>                CryptoAlgo.KeySize = 64
>                Cryptographer = New
>System.Security.Cryptography.CryptoStream(oStmW.BaseStream,
>CryptoAlgo.CreateEncryptor(KEY_8, IV_8), CryptoStreamMode.Write)
>
>                'Setup the text writer with cryptostream instead of
>original stream (Crypto will link them)
>                oXmlW = New XmlTextWriter(Cryptographer, New
>System.Text.UTF8Encoding())
>
>                'Execute the write
>                oXS.Serialize(oXmlW, Game)
>                oXmlW.Close()
>
>
>
>LOADING PORTION
>
>                'Load the new game
>                Dim oXS As XmlSerializer = New
>XmlSerializer(GetType(Game.Game))
>                Dim oStmR As StreamReader
>                Dim oXmlR As XmlTextReader
>
>                'Setup the stream reader
>                oStmR = New StreamReader(pFilename)
>
>                'Setup cryptographic stream cypher
>                Dim CryptoAlgo As New DESCryptoServiceProvider()
>                Dim Cryptographer As
>System.Security.Cryptography.CryptoStream
>                CryptoAlgo.BlockSize = 64
>                CryptoAlgo.KeySize = 64
>                Cryptographer = New
>System.Security.Cryptography.CryptoStream(oStmR.BaseStream,
>CryptoAlgo.CreateEncryptor(KEY_8, IV_8), CryptoStreamMode.Read)
>
>                'Setup the text reader with cryptostream instead of
>original stream (Crypto will link them)
>                oXmlR = New XmlTextReader(Cryptographer)
>
>                'Execute the read
>                oXmlR.WhitespaceHandling =
>WhitespaceHandling.Significant
>                Game = oXS.Deserialize(oXmlR)
>                oXmlR.Close()
>
>Like said earlier, SAVING seems to work fine and outputs a file that is
>encrypted when i open it from notepad, but i may be wrong, maybe it's
>just outputting rubish. The Load definitely doesn't work throwing back
>an InvalidOperationException with the following content, "There is an
>error in the XML document (1, 1)"
>
>Can anyone help please?
>
>
>

24 Sep 2006 6:36 PM

crazyone

Problem is if i don't use an XML reader or XML Writer i can't keep the
line feeds in my descriptive texts. I'd have to provide some complex
HTML content which would output <BR>s insteads of vbCrLfs... Unless you
klnow of a solution to bypass the line feeding problem i have to keep
the text reader/writer...