Re: [TLS] Remarks on draft-shin-tls-augpake-01

[SeongHan Shin <[e-mail]>]

Hi llari,

Thank you for your clarity and feedbacks.

>- What's the endian of bn2bin(X)? Big endian?
>- How are X and Y encoded on the wire? bn2bin?
The draft does not specify the above points because these depend on
implementations.

>- Maybe expand on consequences of terminating on invalid username
I think the current check on authenticators is fine.

>  (allowing probing of valid usernames)?
An orthodox way is to use DHE for encrypting usernames.
This will be added in "Security Considerations" section.

Best regards,
Shin

On Tue, Feb 4, 2014 at 9:50 PM, Ilari Liusvaara <[e-mail]
> wrote:

> On Tue, Feb 04, 2014 at 06:23:16PM +0900, SeongHan Shin wrote:
> > Hi Watson,
> >
> > Thank you for your comments!
> > A simple way to make AugPAKE to be group agnostic is to convert AugPAKE
> to
> > balanced one.
> > Of course, I need to think about other ways.
>
> I think Watson meant generalizing AugPAKE over arbitrary group with
> appropriate hardness properties. Especially elliptic-curve ones.
>
>
> I see nothing that wouldn't map in straightforward manner into elliptic
> curves and only bn2bin(X) that wouldn't map in straightforward manner
> to completely arbitrary group.
>
>
> As for the -1, 0, 1 check, that can be replaced with check that:
> a) The element is valid (e.g. nonzero or satisfies curve equation) AND
> b) The order of element has prime factor of at least q
>
> Those checks are quite cheap with most actually used elliptic curves.
>
>
> Also, some misc feedback:
> - What's the endian of bn2bin(X)? Big endian?
> - How are X and Y encoded on the wire? bn2bin?
> - Maybe expand on consequences of terminating on invalid username
>   (allowing probing of valid usernames)?
>
>
>
> -Ilari
>



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SeongHan Shin
Research Institute for Secure Systems (RISEC),
National Institute of Advanced Industrial Science and Technology (AIST),
Central 2, 1-1-1, Umezono, Tsukuba City, Ibaraki 305-8568 Japan
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