Ok

I need to put a small amount of inforamtion on a public server.
This information should be encoded so as to make it less than easily read
by a human.
I need a program I write to be able to access this info and decrypt it.
This information needs to be checkable as having been created by me and not
messed with by someone else.

I remember learning about Public-Private Key encryption at Uni (Some 8-10
years ago - it all made some kind of sense then.) I remember that once a
private and public key are created, they act more or less like the ying and
yang of each other.

Given an encryption algorithm, if you use 1 key to encrypt then the other
is the key to the decryption.

So I thought I'd encrypt my data using my private key and then have my program
decrypt it with my public key.

I found RSACryptoServiceProvider and set to work creating the following code:
-------------------------------------------------------------
Imports System
Imports System.Security.Cryptography
Imports System.Text
Public Class Cryptography
   Private Shared mPublicKey As String
   Private Shared mPrivateKey As String

   ' This function used only once to generate the Constants above
   Public Shared Sub GenerateKeys()
       Dim RSA As RSACryptoServiceProvider = New RSACryptoServiceProvider()
       mPublicKey = RSA.ToXmlString(False) ' gets the public key
       mPrivateKey = RSA.ToXmlString(True) ' gets the private key
   End Sub

   ' This function should work but throws a runtime error talking about
bad data
   Public Shared Sub TestKeys()
       Call GenerateKeys()
       Dim StartString As String = "Hello EveryBody"
       Debug.Print(String.Format("Start String:'{0}'", StartString))
       Dim EncryptedString As String = EncryptString(StartString, mPrivateKey)
       Dim EndString As String = DecryptString(EncryptedString, mPublicKey)
       Debug.Print(String.Format("End String:'{0}'", EndString))
   End Sub

   ' Utility Funcs
   Private Shared Function EncryptString(ByVal StringToEncode As String,
ByVal KeyInfo As String) As String
       Dim RSAEncoder As New RSACryptoServiceProvider()
       RSAEncoder.FromXmlString(KeyInfo)
       Dim DecodedBytes As Byte() = Encoding.Unicode.GetBytes(StringToEncode)
       Dim EncodedBytes As Byte() = RSAEncoder.Encrypt(DecodedBytes, False)
       Return Convert.ToBase64String(EncodedBytes)
   End Function
   Private Shared Function DecryptString(ByVal EncodedString As String,
ByVal KeyInfo As String) As String
       Dim RSADecoder As New RSACryptoServiceProvider()
       RSADecoder.FromXmlString(KeyInfo)
       Dim EncodedBytes As Byte() = Convert.FromBase64String(EncodedString)
       Dim DecodedBytes As Byte() = RSADecoder.Decrypt(EncodedBytes, False)
       Return Encoding.Unicode.GetString(DecodedBytes)
   End Function
End Class
-------------------------------------------------------------

However I seem to get a "Bad Data" Cryptographic Exception

Can some one tell me where I'm going wrong?

Any help gratefully recieved.

Thanks

--
Ror