Re: Hardcoding RijndaelManaged Keys

From: moondaddy (moondaddy_at_nospam.com)
Date: 03/13/04

  • Next message: Bill Coan: "Re: Word 2003: Smart tags and .NET security and trust all installed addins and templates" 
    Date: Sat, 13 Mar 2004 01:44:41 -0600

    Thanks Shawn, I appreciate the advice and will look into your suggestions. 

    -- 
moondaddy@nospam.com
""Shawn Farkas"" <shawnfa@online.microsoft.com> wrote in message
news:dKfxidKCEHA.600@cpmsftngxa06.phx.gbl...
> Hardcoding keys into your application is not a very secure solution at
all.  It's far too easy to crack open the app, and remove the keys.
> However, before addressing that, let me answer your other questions.
>
> > I was wanting to hardcode the private and public keys on both sides
>
> Let me clarify here -- RijndealManaged is an implementation of the AES
encryption algorithm, which is a symmetric algorithm.  There are no public
> / private keys with a symmetric algorithm, just a single key that both
parties must have.  If you're looking for an algorithm that would use public
and
> private keys (asymetric), then I suggest using RSA.
>
> >Does the Key and IV have to be generated each time data is encrypted, or
can I simply generate them once
>
> The key and IV must be the same on both the server and the client,
otherwise there is no possible way for the server to decrypt the client's
data.
>
> > is there another wait to achieve this like using some sort of
certificate signature on both sides?
>
> Signatures and encryption solve two different problems.  Encryption makes
it difficult for untrusted parties to read your data.  Signatures don't do
> this, instead they make it difficult for untrusted parties to modify your
data.  You may need both properties, in which case you'll need to combine
> encryption and digital signatures.
>
> > If I don't do it the way explained above, then it seems that in order to
send some secure data from the client to the server, the client needs to
first
> request a public key from the server, then encrypt the data using this
public key and send the encrypted data to the server which results in 2
round
> trips and also passing a key around.
>
> This is probably a better method of achieving what you want to do than
hardcoding your key into a client application.  If the key is hardcoded, all
a
> hacker needs to do is get a copy of your client binary, and your entire
security model just got removed.
>
> What I might suggest is distributing the key seperately to each of the few
people who need access to it.  Then have a utility application that uses
> DPAPI to store the key in their machines.  This is probably the most
secure method of achieving what you're attempting to do.
>
> Another (albiet less desirable method) would work if your environment is
very controlled (which it sounds like it is).  If that's the case, I might
> suggest placing the key in a known location under very strict ACLs.  This
way its not coded into the binary, and the client and server both can
> access it.
>
>
> Key management is a very difficult area of cryptography, and it is one of
the most critical.  Before you begin implimenting a solution, I suggest you
> do some reading up on the topic.  I'd start with Michael Howard and David
LeBlanc's Writing Secure Code, Second edition.  They have a chapter
> on key management.  I'd also look up some information on DPAPI and see if
you can't use that to solve your problem.
>
> -Shawn
> http://blogs.msdn.com/shawnfa
>
> -- 
>
> This posting is provided "AS IS" with no warranties, and confers no
rights.
> Note:  For the benefit of the community-at-large, all responses to this
message are best directed to the newsgroup/thread from which they
> originated.
> --------------------
> >From: "moondaddy" <moondaddy@nospam.com>
> >Subject: Hardcoding RijndaelManaged Keys
> >Date: Thu, 11 Mar 2004 13:49:31 -0600
> >Lines: 37
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> >
> >I have a vb.net WinForms app using web services which needs to send
secure
> >data back and forth to the server.  This app will not be widely used and
> >only a few people will have access to it.
> >
> >I was wanting to hardcode the private and public keys on both sides so I
> >wouldn't have to be sending any keys across the wire.  I generate the
keys
> >like this:
> >
> >Dim myRijndael As New RijndaelManaged
> >myRijndael.GenerateKey()
> >myRijndael.GenerateIV()
> >'Get the key and IV.
> >key = myRijndael.Key
> >IV = myRijndael.IV
> >
> >Does the Key and IV have to be generated each time data is encrypted, or
can
> >I simply generate them once, write them to an output, and then hardcode
them
> >into variables on both the server and the client app.  If this isn't
> >possible or is really wrong, then is there another wait to achieve this
like
> >using some sort of certificate signature on both sides?
> >
> >Obviously I'm new at this and need some guidance.  If I don't do it the
way
> >explained above, then it seems that in order to send some secure data
from
> >the client to the server, the client needs to first request a public key
> >from the server, then encrypt the data using this public key and send the
> >encrypted data to the server which results in 2 round trips and also
passing
> >a key around.  If the key were intercepted, then a 'hacker' could use
this
> >key to encrypt his own parameters or data and send that to the server
which
> >the server could then decrypt and posibly use such as inserting a new
user
> >and password which they could then use to hack access into the app.
> >
> >Thanks.
> >
> >-- 
> >moondaddy@nospam.com
> >
> >
> >
>
>
  • Next message: Bill Coan: "Re: Word 2003: Smart tags and .NET security and trust all installed addins and templates"

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