Would it be possible for somebody to give me a better reference pointer to
the document that is begin reference?

 

From: jose [mailto:[email protected]] On Behalf Of Richard Barnes
Sent: Wednesday, February 12, 2014 4:28 PM
To: Brian Campbell
Cc: [email protected]
Subject: Re: [jose] question about the size of coordinate parameters in EC
JWKs

 

That would make sense only for binary curves, but most of the curves people
use today are integer curves, in which case truncation is totally sensible.


 

I've been told that some Microsoft crypto libraries use fixed-length buffers
for these things, but there should be a problem copying a shorter value into
that buffer.

 

Net of that, I would be in favor of saying that the coordinates MUST be
full-length for binary curves, and MAY be zero-padded to full length for
integer curves.

 

--Richard

 

On Wed, Feb 12, 2014 at 6:58 PM, Brian Campbell <[email protected]>
wrote:

Could anyone in this fine WG explain (probably again, I missed it the first
time) the rational behind the text 'The length of this octet string MUST be
the full size of a coordinate for the curve specified in the "crv"
parameter.', which is in the definitions of the X and Y Coordinate
parameters for EC keys in JWA [1]?

This message last month on the list
http://www.ietf.org/mail-archive/web/jose/current/msg03901.html and an off
list message indicate that both the jose4j and Nimbus JOSE+JWT
implementations aren't following spec on the length of the octet string
being the full size of a coordinate for the curve. Which suggests that there
maybe potential interoperability problems with certain EC JWKs.  

I'm just trying to wrap my head around the issue so any help in that would
be appreciated. 


[1]
http://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-20#section-6.
2


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