[Cfrg] small editorial error in and question on draft-irtf-cfrg-dragonfly-01 (was: Re: CFRG meeting at IETF 87)

Hi Dan:

I just quickly revisited the "password to point" mapping for elliptic 
curves in draft-irtf-cfrg-dragonfly-01 (Section 3.2.1) and noticed a 
small error: the seed is recursively defined. Fortunately, this is easy 
to fix, as follows:

was:

    base = H(max(Alice,Bob) | min(Alice,Bob) | password | counter)
    seed = KDF-n(seed, "Dragonfly Hunting And Pecking")

suggested change:

    base = H(max(Alice,Bob) | min(Alice,Bob) | password | counter)
    seed = KDF-n(base, "Dragonfly Hunting And Pecking")

On a more general note, with the draft rev1 version, the found point Q 
is a function of the password itself and the presumed key sharing 
parties Alice and Bob. In other words, the password-derived generator of 
the curve "PE Element" is fixed throughout the lifetime of the pair 
(password, key sharing parties). With draft-harkins-tls-pwd-03, a 
similar procedure is proposed, but there a "salt" is mixed in as well. 
Just curious: why the difference? 
<http://tools.ietf.org/pdf/draft-harkins-tls-pwd-03.pdf>

Best regards, Rene

On 7/26/2013 5:50 PM, David McGrew wrote:
> Hi,
>
> here is the agenda for our upcoming meeting; we are looking forward to
> seeing you there.
>
> David and Kevin
>
> ---
>
> Crypto Forum Research Group at IETF 87
> Monday, July 29, 2013
> 1510-1610  Afternoon Session II
> Room: Tiergarten 1/2
>
> Agenda Bashing
>
> Randomized Hashing (as described in NIST SP-800-106/107) - Quynh Dang
>
> Updates on active drafts
>
>   - OCB Mode of Operation, draft-irtf-cfrg-ocb-03
>
>   - Dragonfly Key Exchange, draft-irtf-cfrg-dragonfly-01
>
>   - Hash-Based Signatures, draft-mcgrew-hash-sigs-00
>
> "Selection of Future Cryptographic Standards", Sheffer, Grieco, McGrew.
> draft-mcgrew-standby-cipher-00
>
> Discussion on other crypto work
>    Salsa20
>    DTLS In Constrained Environments (DICE)
>    CAESER
>
>
> _______________________________________________
> Cfrg mailing list
> Cfrg@irtf.org
> http://www.irtf.org/mailman/listinfo/cfrg

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