[Cryptography-dev] accessing elliptic curve domain parameters (a/b/p/etc)

Matt Bullock matt.s.b.42 at gmail.com
Sun Mar 20 11:53:40 EDT 2016


I see that the pull request[1] relevant to this was denied last week due to
the API surface.  For my own understanding, what would be required for
these values to be approved to be available through this library
(cryptography)?  Once I have time I'm planning to contribute the point
compression code that I wrote for my project, but the point decompression
algorithm requires these curve parameter values.

thanks
   --Matt

[1] https://github.com/pyca/cryptography/pull/2499

On Wed, Jan 27, 2016 at 11:18 PM Matt Bullock <matt.s.b.42 at gmail.com> wrote:

> Yup, that looks like that would cover exposing the values I need.  I was
> originally thinking pulling them from the backend, but I guess this way
> it's independent of the backend implementation (and it's not like the
> values will change).  I'll keep an eye on those pull requests and plan that
> part of my code to adopt them once they're in a release.
>
> thanks
>    --Matt
>
> On Wed, Jan 27, 2016 at 8:44 PM Matt Bullock <matt.s.b.42 at gmail.com>
> wrote:
>
>> Nice, thanks, I'll take a look at that once GitHub is back up.
>>
>>    --Matt
>>
>> On Wed, Jan 27, 2016 at 8:39 PM Paul Kehrer <paul.l.kehrer at gmail.com>
>> wrote:
>>
>>> Hi Matt,
>>>
>>> There are multiple issue/pull requests for this but unfortunately GitHub
>>> is down at the moment so I can't look them up... Once GitHub is back up and
>>> running take a look at https://github.com/pyca/cryptography/pull/2476 (that
>>> PR might have been split into other PRs that we've been discussing, but
>>> hopefully we've cross linked them)
>>>
>>> Please weigh in on that as knowing all the potential consumers helps us
>>> decide whether the increase in API surface area is worthwhile.
>>>
>>> -Paul Kehrer (reaperhulk)
>>>
>>> On January 27, 2016 at 7:34:28 PM, Matt Bullock (matt.s.b.42 at gmail.com)
>>> wrote:
>>>
>>> For a project I am working on, I have a need to encode/decode elliptic
>>> curve points using point compression[1].  As this is not yet supported
>>> natively by the cryptography library, I have started implementing it myself
>>> but have hit a snag.  Unlike the uncompressed point encoding, in order to
>>> decode a compressed curve point I need to be able to reference the curve
>>> parameters.  I have been searching through the cryptography documentation
>>> and code but cannot find any way of retrieving these values from the
>>> backend.
>>>
>>> Is there a method for this that I am missing, or is this functionality
>>> not yet available?
>>>
>>> thanks
>>>    --Matt
>>>
>>> [1] 2.3.3/2.3.4 http://www.secg.org/sec1-v2.pdf
>>>
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>>
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