Re: [openpgp] Sec. Considerations MUST about S2K [was: Re: I-D Action: draft-ietf-openpgp-crypto-refresh-02.txt]

Ángel <angel@16bits.net> Sun, 28 February 2021 22:09 UTC

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Date: Sun, 28 Feb 2021 23:09:03 +0100
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Subject: Re: [openpgp] Sec. Considerations MUST about S2K [was: Re: I-D Action: draft-ietf-openpgp-crypto-refresh-02.txt]
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On 2021-02-28 at 03:46 +0000, Peter Gutmann wrote:
> Daniel Kahn Gillmor <dkg@fifthhorseman.net> writes:
> 
> > I'm not sure about this at all.  For example, consider a system
> > that knows
> > that the string is high-entropy ("good key equivalent") -- should
> > they be
> > prohibited from using Simple or Salted S2K?  Is this MUST really an
> > interoperability concern as §6 of RFC 2119 suggests?
> 
> Agreed, but it's a pretty simple fix:
> 
>   Where it's likely that a low-entropy secret is being employed, a
> compliant
>   application SHOULD use [...]
> 
> Peter.


I would suggest a didactic approach, something like
> Simple S2K and Salted S2K specifiers are not particularly secure 
> when used with a low-entropy secret, such as those typically provided
> by users, and implementations SHOULD avoid using these methods on
> encryption of both keys and messages.


Best regards