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Re: [Trans] Question regarding new gossip protocols [Was: Certificate transparency on blockchains]

paul@nohats.ca Fri, 27 March 2015 22:37 UTC

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Date: Fri, 27 Mar 2015 18:36:56 -0400
From: paul@nohats.ca
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Subject: Re: [Trans] Question regarding new gossip protocols [Was: Certificate transparency on blockchains]
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On Fri, 27 Mar 2015, Tao Effect wrote:

> To illustrate:
> 
> A = server's real certificate
> B = malicious MITM certificate
> 
> T1. Client receives A.
> T2. Client receives B, sends back A.
> T3. MITM pretends to leave, sends A. Client sends B.

T3 cannot happen. The draft states:

    SCTs and corresponding certificates are POSTed to the originating
    HTTPS server at the well-known URL:

    https://<domain>/.well-known/ct/v1/sct-feedback

This means you must have a valid TLS connection to send the data. As
long as the attacker does not have the private key of the attacked
web server, this cannot happen.

> So, my question is: does your document properly take that into account and state that the data sent in 3.1.3 *must* be sent after a
> fully encrypted TLS connection has been established?

Yes, but I'm sure the authors would love to received improved text for
this section of the document.

> P.S. FYI Paul, any time I CC your email I get a bounced "Undelivered Mail" response:
>
>       Final-Recipient: rfc822; cypherpunks@nohats.ca
> Original-Recipient: rfc822;paul@cypherpunks.ca
> Action: failed
> Status: 5.1.1
> Remote-MTA: dns; 193.110.157.102
> Diagnostic-Code: smtp; 550 5.1.1 <cypherpunks@nohats.ca>: Recipient address
>    rejected: User unknown in local recipient table

Sorry about that. I added an alias to fix it. (my home DSL is down so
mail is rerouted temporarily, and I'm far from home)

Paul

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