On 10/18/11 12:11 PM, Andrew Sullivan wrote:
> On Tue, Oct 18, 2011 at 11:53:43AM -0600, Peter Saint-Andre wrote:
>> On the SAAG list, Mike Parker expressed concerns about mandating that
>> passwords MUST be Unicode, because some systems store passwords as octet
>> strings...
> 
> Right.  Precis can hardly dictate what programs not implementing its
> specifications do, any more than precis can go back in time and cause
> applications to do this.  (Compare this with the IDNA2008 MUSTs: every
> non-compliant fake A-label is still a perfectly good DNS label.
> Indeed, the string "can't" is not a legal IDNA2008 label, but it's a
> valid DNS label anyway.)
> 
>> Instead, it's giving protocol designers a common tool for preparing and
>> comparing passwords (and other strings) containing Unicode characters,
>> if they choose to support such things.
> 
> Exactly: if you want to do precis, then it MUST be Unicode.  Behaviour
> for strings that are not Unicode, including binary blobs and any other
> character encoding, is undefined.

Agreed with all that.

>> However, we might want to provide some text in the security
>> considerations about the desirability (or not) of full-Unicode passwords.
> 
> I'm slow, but what's the security consideration?  There are
> interoperability considerations: if two applications want to
> co-operate in authentication, then they're going to need to use
> Unicode or make up their own protocol.  

Right, it's text about interoperability. Where exactly that belongs is
another matter. I'm happy to add a section about interoperability.

Peter

-- 
Peter Saint-Andre
https://stpeter.im/


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