Re: [TLS] New draft: draft-ietf-tls-tls13-14.txt

["Dang, Quynh (Fed)" <[e-mail]>]

Hi Eric and all,

In my opinion, we should give better information about data limit for AES_GCM in TLS 1.3 instead of what is current in the draft 14.

In this paper: http://www.isg.rhul.ac.uk/~kp/TLS-AEbounds.pdf,  what is called confidentiality attack is the known plaintext differentiality attack where the attacker has/chooses two plaintexts, send them to the AES-encryption oracle.  The oracle encrypts one of them, then sends the ciphertext to the attacker.  After seeing the ciphertext, the attacker has some success probability of telling which plaintext was encrypted and this success probability is in the column called "Attack Success Probability" in Table 1.  This attack does not break confidentiality.

If the attack above breaks one of security goal(s) of your individual system, then making success probability of that attack at 2^(-32) max is enough. In that case, the Max number of records is around 2^38.


Regards,
Quynh.



Date: Monday, July 11, 2016 at 3:08 PM
To: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: [TLS] New draft: draft-ietf-tls-tls13-14.txt

Folks,

I've just submitted draft-ietf-tls-tls13-14.txt and it should
show up on the draft repository shortly. In the meantime you
can find the editor's copy in the usual location at:

  http://tlswg.github.io/tls13-spec/

The major changes in this document are:

* A big restructure to make it read better. I moved the Overview
  to the beginning and then put the document in a more logical
  order starting with the handshake and then the record and
  alerts.

* Totally rewrote the section which used to be called "Security
  Analysis" and is now called "Overview of Security Properties".
  This section is still kind of a hard hat area, so PRs welcome.
  In particular, I know I need to beef up the citations for the
  record layer section.

* Removed the 0-RTT EncryptedExtensions and moved ticket_age
  into the ClientHello. This quasi-reverts a change in -13 that
  made implementation of 0-RTT kind of a pain.

As usual, comments welcome.
-Ekr



* Allow cookies to be longer (*)

* Remove the "context" from EarlyDataIndication as it was undefined
  and nobody used it (*)

* Remove 0-RTT EncryptedExtensions and replace the ticket_age extension
  with an obfuscated version. Also necessitates a change to
  NewSessionTicket (*).

* Move the downgrade sentinel to the end of ServerHello.Random
  to accomodate tlsdate (*).

* Define ecdsa_sha1 (*).

* Allow resumption even after fatal alerts. This matches current
  practice.

* Remove non-closure warning alerts. Require treating unknown alerts as
  fatal.

* Make the rules for accepting 0-RTT less restrictive.

* Clarify 0-RTT backward-compatibility rules.

* Clarify how 0-RTT and PSK identities interact.

* Add a section describing the data limits for each cipher.

* Major editorial restructuring.

* Replace the Security Analysis section with a WIP draft.

(*) indicates changes to the wire protocol which may require implementations
    to update.