Re: Asymmetric encryption questions

From: Chad Myers (cmyers@N0.S.P4.M.austin.rr.com)
Date: 06/20/02 

From: "Chad Myers" <cmyers@N0.S.P4.M.austin.rr.com>
Date: Thu, 20 Jun 2002 09:22:38 -0500

"FullMetalAnorak" <ollie.riches@hotmail.com> wrote in message
news:eKOkYLEGCHA.2544@tkmsftngp08...
> Hi,
>
> I want to use public, private key encryption so after looking at the help
I
> am going to use RSACryptoProvider, I see that if I want to serialize out
the
> public, private keys I use the method 'ExportParameters' that returns the
> RSAParameters object which can be serialized as XML.
>
> Does this contain all the information required to recreate an
> RSACryptoProvider?

Yes.

>
> Does this contain both the public and private keys?

It always contains the public, but the "exportPrivateData" flag
on the ExportParameters() method determines whether it exports
the private key.

>
> Do I need to extract out the public key for my client or just provide all
> the information from the serialized object?
>
> Can you persist the keys generated in the RSACryptoProvider?

Yes. You can write the bytes or xml to a file, however, storing private
key data is a bad practice unless you do so according to key storage
standards.

.NET has no managed support for secure key storage. You must use
the unmanaged Win32 CryptoAPI methods for storing keys securely.

What I think you're looking to do is do key exchange. If you want
to create an encrypted session, you should generate a keypair
on the server, then use something like RSAOAEPKeyExchangeFormatter
and Deformatter to properly send the server's public key to the
client. Then, using that new RSA encrypted channel, you can send
the session key for your TripleDES (or other symmetric alg)
encryption session.

It's not a good idea to use RSA to do full encryption as its
slower than symmetric algorithms such as TripleDES or Rijndael.

-c

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