The assumed attack profile is a MITM insertion into a connection stream between server and client whereby the attacker gains complete unencrypted access to all traffic over the connection, not just meta data.
TLS already has a built-in concept of "strong authentication" between server and client to defeat this attack. It requires that the TLS server pre-obtain by some secondary channel the public key of the user. This proposal eliminates that requirement by making the user's public keys public knowledge. Karl From: Jon Callas [mailto:[email protected]] Sent: Thursday, September 12, 2013 06:21 To: Karl Malbrain Cc: Jon Callas; Phillip Hallam-Baker; Theodore Ts'o; [email protected] Subject: Re: [perpass] proposed enhancement to TLS strong authentication protocol On Sep 11, 2013, at 11:56 AM, Karl Malbrain <[email protected]<mailto:[email protected]>> wrote: The goal of the proposal is to enable the use of strong authentication for all TLS connections over the internet. The certificates as things-in-themselves don't really matter, they are actually just a vehicle to post the public key of the user/server in a reliable public place. The security occurs when the challenges to prove private key ownership are cross-issued by each party. MITM would not have the private keys to answer either challenge. Note that this still doesn't solve the problem of MITM obtaining the server's private key. I'm still working on that one. I might be misunderstanding, but it seems to me that your global directory would allow a passive listener to fingerprint the client by sniffing in a variety of places -- near the client, near the server, or near the directory. If you assume an attacker interested in collecting metadata about the clients, this would be suboptimal. I may be missing something, but this sounds like it is just a global, central certificate authority, albeit one that is not actually issuing the certificates, but still assigning them GUIDs, which are by definition globally unique. Am I indeed missing something? Jon
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