> If I have an x-point which follows this representation > https://tools.ietf.org/id/draft-jivsov-ecc-compact-05.html (so it is > composed by 33 byte and first byte is '0x02') and I use > 'EC_POINT_set_compressed_coordinates_GFp' function, it will be > considered as compressed-y-0 or compressed-y-1? Or it is correctly > considered as the x coordinate?
What you are saying and what you are doing are two different things. Your code is at a very low level. Above this there is some encoding of points, depending on any number of standards. OpenSSL implements some of them, but at a higher level. The low level API you're talking about provides maximum flexibility to map that high level encoding in to the API's "x-coord + y-bit" concept. It's up to you to figure out the details. (Including determining if the encoding in OpenSSL matches what's expected in your spec.) You need to play around a bit with the lib -- you can't expect this list to interpret the standard for you. Check the "test" folder for sample code. BBB
