Re: [http-auth] Mirja Kühlewind's No Objection on draft-ietf-httpauth-mutual-10: (with COMMENT)

大岩寛 <> Wed, 02 November 2016 08:55 UTC

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From: 大岩寛 <>
To: Mirja Kuehlewind <>, The IESG <>
Thread-Topic: Mirja Kühlewind's No Objection on draft-ietf-httpauth-mutual-10: (with COMMENT)
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Subject: Re: [http-auth] Mirja Kühlewind's No Objection on draft-ietf-httpauth-mutual-10: (with COMMENT)
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Dear Mirja, thank you very much for the comments.

> One important question:
> Doesn't this spec need to register a new HTTP Authentication Schemes
> ("Mutual") with IANA?

As Julian suggested, yes.
We'll add one more clause to IANA consideration.

> Further minor comments/questions:

> 1) Somehow I don't understand this:
> "For responses, the parameters "reason", any "ks#" (where # stands
>       for any decimal integer), and "vks" are mutually exclusive; any
>       challenge MUST NOT contain two or more parameters among them.
>       They MUST NOT contain any "kc#" or "vkc" parameters."
> Who is 'they' in the last sentence?
We'll change it to "the responses".

> 2) "Typically, clients can ensure the above property by using a
>    monotonically-increasing integer counter that counts from zero up to
>    the value of nc-max."
> Wouldn't it be better to use a randomized number?

This is by design.
Use of an almost-sequential counter makes efficient detection of
replayed challenges be possible with constant memory space.
Using random numbers, the servers must remember all used nonces
to detect replays, which requires memory space proportional to
the lifetime of the "shared key" (z in the specification).
In this algorithm, shared keys are cryptographically generated
"strong secrets", so use of sequential counters will not decrease
the security strength of the whole protocol significantly.
Replay attacks are more important to be prevented.

> 3) Nit: s/Even if the request-URI does not have a port part, v will include
> the default port number./Even if the request-URI does not have a port part,
> vh will include the default port number./

Thank you.

Yutaka OIWA, Ph.D.       Leader, Cyber Physical Architecture Research Group
                                  Information Technology Research Institute
    National Institute of Advanced Industrial Science and Technology (AIST)
                      Mail addresses: <>, <>
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