Re: [openpgp] [eX-bulk] : Re: Fingerprints

["Christopher LILJENSTOLPE" <[e-mail]>]

Ooops, forgot to reassert the bit....


</proto-hat off>


On 6 May 2015, at 11:33, Christopher LILJENSTOLPE wrote:

> <proto-hat off>
>
>> On 6 May 2015, Werner Koch wrote:
>>> To be future proof we should get away from SHA-1 for fingerprints
>>> and use SHA-256 (or SHA-512) instead.
>>
>> I have no quarrel with changing the hash algo.  If it improves security
>> at no cost of usability or complexity - go for it.
>>
>>> The external representation and even the internal use in OpenPGP is a
>>> different issue and I am all in favor for truncating it to 32 bytes
>>> for internal use and printing only up to 20 bytes.  This avoids extra
>>> work and SHA-256 is anyway required.
>>
>> Sounds good to me.  I'm just afraid that if "something stronger" is
>> available, people are going to use it.  Design decisions and established
>> culture on top of the standard tend to be maximum conservative.  Sort of
>> if you don't use the "full fingerprint" you're not doing "everything you
>> can" and people will use all 32 bytes no matter if it was ever intended
>> that way.  That's not a huge deal, we just need to keep it in mind.
>>
>> I would leave the fingerprint length at 20 bytes in the standard, if an
>> implementation chooses to use more internally that's up to them.
>> Defining the fingerprint to be 32 bytes, then adding "for printing, it
>> SHOULD be truncated to 20 bytes" seems silly.
>
> I think this is a reasonable approach.  The phrasing I would use would be something along the lines of:
>
> Any implementation MUST accept a 20 byte fingerprint for validation, consisting of the first 20 bytes of the calculated fingerprint.
> An implementation MAY output, or accept, a longer fingerprint, if desired.
> An implementation MAY output, or accept, the legacy SHA-1 fingerprint, for interoperability, but it's use SHOULD be discouraged.
>
> The use of RFC 4648 would make things easier, btw, and also signal the new fingerprint model.
>
> The concept will be familiar to anyone who uses git, btw.
>
>
> 	Christopher
>
>>
>> - V
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>
>
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> 李柯睿
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李柯睿
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