Re: [Cfrg] I-D Action: draft-irtf-cfrg-augpake-05.txt

Oops my mistake, no that attack doesn't work. Thanks to Rene Struik for
pointing out my mistake.

Mike

On Fri, Jan 22, 2016 at 1:17 PM, Michael Scott <mike.scott@miracl.com>
wrote:

> Appears to be a small weakness here, assuming that the actual password w
> is used "the binary representation of the processed UTF-8 character
> string"
>
> A false server who wants to eliminate some password guesses from their
> list, responds with
>
> Y=(X^y.g^(w*r*y))^n where they wish to eliminate passwords w,2w,3w,... nw
>
> The user responds with a hash of known quantities, plus Y^{1/(x+wr)} =
> g^{ny}
>
> The false server drops the link, and offline checks for the correct value
> of n. If its not there, then w,2w,3w,.. nw can be eliminated.
>
>
> Mike
>
> On Fri, Jan 22, 2016 at 1:13 AM, <internet-drafts@ietf.org> wrote:
>
>>
>> A New Internet-Draft is available from the on-line Internet-Drafts
>> directories.
>>  This draft is a work item of the Crypto Forum Working Group of the IETF.
>>
>>         Title           : Augmented Password-Authenticated Key Exchange
>> (AugPAKE)
>>         Authors         : SeongHan Shin
>>                           Kazukuni Kobara
>>         Filename        : draft-irtf-cfrg-augpake-05.txt
>>         Pages           : 20
>>         Date            : 2016-01-21
>>
>> Abstract:
>>    This document describes a secure and highly-efficient augmented
>>    password-authenticated key exchange (AugPAKE) protocol where a user
>>    remembers a low-entropy password and its verifier is registered in
>>    the intended server.  In general, the user password is chosen from a
>>    small set of dictionary whose space is within the off-line dictionary
>>    attacks.  The AugPAKE protocol described here is secure against
>>    passive attacks, active attacks and off-line dictionary attacks (on
>>    the obtained messages with passive/active attacks).  Also, this
>>    protocol provides resistance to server compromise in the context that
>>    an attacker, who obtained the password verifier from the server, must
>>    at least perform off-line dictionary attacks to gain any advantage in
>>    impersonating the user.  The AugPAKE protocol is not only provably
>>    secure in the random oracle model but also the most efficient over
>>    the previous augmented PAKE protocols (SRP and AMP).
>>
>>
>> The IETF datatracker status page for this draft is:
>> https://datatracker.ietf.org/doc/draft-irtf-cfrg-augpake/
>>
>> There's also a htmlized version available at:
>> https://tools.ietf.org/html/draft-irtf-cfrg-augpake-05
>>
>> A diff from the previous version is available at:
>> https://www.ietf.org/rfcdiff?url2=draft-irtf-cfrg-augpake-05
>>
>>
>> Please note that it may take a couple of minutes from the time of
>> submission
>> until the htmlized version and diff are available at tools.ietf.org.
>>
>> Internet-Drafts are also available by anonymous FTP at:
>> ftp://ftp.ietf.org/internet-drafts/
>>
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>
>