Re: [keyassure] Bare keys again

[Paul Wouters <[e-mail]>]

On Mon, 21 Mar 2011, Martin Rex wrote:

> See http://tools.ietf.org/html/rfc5246#section-7.4.2
>
>   When this message will be sent:
>
>      The server MUST send a Certificate message whenever the agreed-
>      upon key exchange method uses certificates for authentication
>      (this includes all key exchange methods defined in this document
>      except DH_anon).  This message will always immediately follow the
>      ServerHello message.
>
> which part of the "MUST send" is unclear to you?
>
> What might be slighly misleading in that section is that it
> defines a handshake message that is used in two situations
> (Server Certificate and Client Certificate) and the semantics of an
> empty Certificate handshake message is only defined for the
> "Client Certificate" handshake message, but _NOT_ for the Server Certificate
> handshake message.

Section 7 of 5246 shows me:

     Client                                               Server

       ClientHello                  -------->
                                                       ServerHello
                                                      Certificate*
                                                ServerKeyExchange*
                                               CertificateRequest*
                                    <--------      ServerHelloDone
       Certificate*
       ClientKeyExchange
       CertificateVerify*
       [ChangeCipherSpec]
       Finished                     -------->
                                                [ChangeCipherSpec]
                                    <--------             Finished
       Application Data             <------->     Application Data

* Indicates optional or situation-dependent messages that are not
    always sent.

To me this seems to say that "Certificate*" on the server side could
be omitted in situation-dependent messages.

Paul