[openssl-users] ec_point_is_compat

john.hughes at secid.co.uk john.hughes at secid.co.uk
Thu Jan 24 20:26:41 UTC 2019

In a test harness I'm writing I'm adding in a facility to check the validity
of an EC public key according to the 4 tests of X9.62.


The curve and point I supply to EC_POINT_is_at_infinity works fine.


However, when I come to use EC_POINT_is_on_curve it fails. The error return
indicates the error is "incompatible objects". Looking through the openssl
source indicates that the error is a result of failing one of the tests in
the inline function ec_point_is_compat.  In this function there are four
simple tests - most of which pertains to looking at the values of curve_name
in the EC_POINT and EC_GROUP structures.  So I thought, quite simply, look
at what these two structures hold pertaining to the member curve_name - and
then I can figure out what I'm doing wrong.


The openssl interface has the function EC_GROUP_get_curve_name() which I
used to show that curve name was 409 (for NIST P192) and 415 (for NIST
P256). But to my surprise there was no function of


Has any one any suggestions why my code is failing the ec_point_is_compat
tests and how to get hold of the values of meth and curve_name in my
EC_GROUP and EC_POINT structures so I can determine why the checks are









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