Re: [babel] Shepherd's review of draft-ietf-babel-hmac-02
Juliusz Chroboczek <jch@irif.fr> Wed, 26 December 2018 19:03 UTC
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Date: Wed, 26 Dec 2018 20:03:12 +0100
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From: Juliusz Chroboczek <jch@irif.fr>
To: Donald Eastlake <d3e3e3@gmail.com>
Cc: Babel at IETF <babel@ietf.org>, babel-chairs <babel-chairs@ietf.org>, draft-ietf-babel-hmac@ietf.org
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Archived-At: <https://mailarchive.ietf.org/arch/msg/babel/h0-c_yi0IdQQECBCioIWkThfDu4>
Subject: Re: [babel] Shepherd's review of draft-ietf-babel-hmac-02
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Thanks for your review, Donald. > "robust random number generator" -> "robust random number [RFC4086] > generator". Could also add the RFC 4086 reference at other occurrences > of "random" but reference should be included at least once. Done, thanks. > Section 1.2, Top of page 4, third bullet item. > This is a little confusing to read. I assume that the point about the > packet being accepted by node A is that it's a valid packet (has a > good HMAC TLV). But I think the average reading will be wondering > "What is this node A and why isn't it mentioned again later?" Not sure > if there is a reasonable wording change that improves this... I too am unhappy with this property. We've spent a lot of time thinking about how to reformulate it in a more comprehensible manner, but we've failed. If anyone has any idea, I'm listening. > Section 5.2: > The diagram is odd. I would recommend sliding the Index field and > preceding vertical bar character to the left so it starts aligned > with the Type. I've tried, but I didn't like the result. I'll leave it as it is, if that's okay with you. > Also, the PC is fixed length, which is not shown in the figure - I think > you really have to at least mention the length of the PC in this > section. Done. > While it is reasonable, for implementation convenience, that there is > a maximum size for Index, perhaps for cryptographic strength, there > should be a minimum length, maybe 12 bytes? I disagree. The only property that the index needs to satisfy is that it is never reused for a different PC sequence for a given (key, sender) pair. In particular, if a node never loses state (e.g. it has reliable persistent storage), then it never needs to change indices -- and in that case, a 0-octet index is suitable. > Thinking some more about PC, seems like you either (1) need to say > that circular arithmetic is used [rfc1982] (bad idea in my opinion), > or (2) say what happens when PC hits all 1's (presumably adopt a new > Index, probably a better idea). It might be useful to also state that > PC is an "unsigned integer" or the like. In Section 4.2, we say: if the PC overflows, a new index is generated; In Section 5.2, we say: A new index MUST be generated whenever the PC overflows. Please let me know if you think that's not explicit enough. > Should say IANA is "requested" rather than "instructed". Done. > Heading should end with "-hmac-01", not "-hman-00". Done. Thanks again, -- Juliusz
- [babel] Shepherd's review of draft-ietf-babel-hma… Donald Eastlake
- Re: [babel] Shepherd's review of draft-ietf-babel… Juliusz Chroboczek
- Re: [babel] Shepherd's review of draft-ietf-babel… Dave Taht
- Re: [babel] Shepherd's review of draft-ietf-babel… Juliusz Chroboczek
- Re: [babel] Shepherd's review of draft-ietf-babel… Donald Eastlake
- Re: [babel] Shepherd's review of draft-ietf-babel… Gabriel Kerneis