Re: [Cfrg] Review of draft-irtf-cfrg-argon2-02

Russ Housley <housley@vigilsec.com> Fri, 23 June 2017 21:28 UTC

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From: Russ Housley <housley@vigilsec.com>
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Date: Fri, 23 Jun 2017 17:28:21 -0400
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Subject: Re: [Cfrg] Review of draft-irtf-cfrg-argon2-02
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I meant to say:

Once the comments below are resolved, I think that the IRSG should
publish the document.

Russ



> On Jun 23, 2017, at 5:19 PM, Russ Housley <housley@vigilsec.com> wrote:
> 
> Document: draft-irtf-cfrg-argon2-02
> Reviewer: Russ Housley
> Review Date: 2017-06-23
> 
> Summary: Almost Ready
> 
> Once the comments below are resolved, I think that the ISE should
> publish the document.
> 
> 
> Major Concerns:
> 
> Section 3.3: The pseudo-code includes this line:
> 
>               V_{r+1} = H_{T-32*r}(V_{r})
> 
> Up to this point, I thought that the Argon2 construction could work with
> many different hash functions, but at this point I realized that Argon2
> depends the ability of Blake2b to produce an output between 1 and 64
> bytes.  Please add a sentence or two to the introduction so that others
> can avoid this misunderstanding.
> 
> Section 3.5: This section defines the compression function G.  It makes
> use of the BLAKE2b round function P, which is explained in Section 3.6.
> Section 3.6 defines another function G, which is different than the 
> compression function.  I realize that both G functions are discussed in
> other documents ([I-D.saarinen-blake2] and [ARGON2]), but there ought to
> be a way to avoid this name collision.
> 
> Section 5: I tried to compile the code, and it does not work with gcc.
> Is there a missing include file?
> 
> 
> Minor Concerns:
> 
> 
> Section 2 defines "E_f" as a variable E with subscript index f; however,
> in Section 3.3, defines "H_x" as a hash function with x-byte output.
> Please use a different notation for variables and functions.
> 
> Section 5: A main function would make it easier to use this reference
> code.  Can you include something simple?  Perhaps something that prints
> the tags associated with the test vectors in Section 6.
> 
> 
> Nits:
> 
> Section 1: s/implementer oriented/implementer-oriented/
> 
> Section 1: s/data-depending memory access/data-dependent memory access/
> 
> Section 2: Please add a descriptions for the floor and ceil functions.
> 
> Section 2: Please add a description for length(P), which always returns
> 32 bits.
> 
> Section 2 defines "a ^ b", but Sections 3.2 and 3.5 use "a XOR b".
> Pick one.
> 
> Most of the document uses "=" for assignment, but Section 3.6 uses "<-".
> Please use "=" throughout.
> 
> Several places, the document tells us that "integers are padded to 4
> bytes and encoded in little endian".  Maybe a "uint32" function should
> be specified to avoid repeating this phrase.
> 
> Section 3.2: s/described in later section./described in later sections./
> 
> Section 6.3: Please correct the formatting.
> 
> Section 9.1: s/calls to Blake2b is needed/calls to Blake2b are needed/
> 
> Section 9.2: s/number t of passes/the number of passes, t,/
> 
> Section 9.3: s/for Argon2i 3 passes/for Argon2i, 3 passes/
> 
> Section 9.3: s/for Argon2d and Argon2id 1 pass/for Argon2d and Argon2id, 1 pass/
> 
> 
> Personal preference:
> 
> Section 3.5: s/applied rowwise, and then columnwise/
>              /applied to each row, and then to each column/
> 
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