[Cryptography-dev] Using EC Point arithemtic in cryptography

[John Pacific]

Hey, Alex!

Thanks for the response! I've been using the ECDH API for the scalar
multiplication, but my last remaining need is for `BN_mod_inverse` and I
can't seem to find anything on that quite yet. No pointers here, I guess?


Thanks!

-John

On Fri, Dec 1, 2017 at 3:24 PM, Alex Gaynor <alex.gaynor at gmail.com> wrote:

> Hi John,
>
> We don't have an API for doing raw EC point arithmetic. https://github.
> com/pyca/cryptography/pull/2919 is an issue proposing (and implementing)
> it, but I've been very hesitant to expand the API like this.
>
> Point multiplication can be accomplished with the ECDH API.
>
> Alex
>
> On Fri, Dec 1, 2017 at 2:47 PM, John Pacific <me at johnpacific.com> wrote:
>
>> Hey, folks!
>>
>> I'm working on prototyping this cryptosystem using cryptography. I'm
>> porting it from Charm-crypto in Python to this.
>>
>> Charm crypto overrides some operators to perform scalar multiplication
>> and modular inverses -- ie: `*` and `~`. When these operators are used with
>> an EC element, it performs the overriden operation.
>>
>> I am now in the need to perform some similar operations within the
>> context of cryptography.io and I can't seem to find a great way to do
>> this.
>>
>> I can access some OpenSSL functions like `EC_POINT_mul` and
>> `BN_mod_inverse` via `default_backend()._lib.EC_POINT_mul`, etc but I
>> can't find any documentation of how this is used within the context of
>> cryptography.io.
>>
>> Do any of you wonderful folks have any pointers on this or maybe how to
>> perform some point arithmetic with the cryptography objects?
>>
>>
>> Thanks,
>>
>> tux
>>
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>
>
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