Compute EC_KEY starting from X or Y coordinate only

Luca Di Mauro luca.dimauro at
Fri Oct 25 06:28:39 UTC 2019

I think it is correct because I extracted the hexadecimal string from  
a packet contained in a pcap.

This compressed point is created following the ETSI TS 103 097 v1.3.1  
standard for secured communications in the vehicular communication  

I notice that the point 'pubPoint' that I created is empty when I try  
to call 'EC_POINT_set_compressed_coordinates_GFp' function. How can I  
put a BIGNUM into an EC_POINT?


Billy Brumley <bbrumley at> ha scritto:

>>         EC_GROUP* group         = EC_GROUP_new_by_curve_name  
>> (NID_secp256k1);
>> "c16b4ce0532f5dc9d09114fe121d3956ae84f9eb677a0d4bdac1d3af7a91950c";
> I don't believe there's a point on secp256k1 with that x-coordinate.
> If you check the failure reason for
> EC_POINT_set_compressed_coordinates_GFp in the debugger, that is
> probably what it is telling you.
> Where did this curve / x-coord pair come from?

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