I understand for prime curves it is just
bytes(0x02 + flag) + bytes(x)
where flag is the LSB of
y. For the F2m curves I cannot make out how to do it.
IEEE P1363 section 22.214.171.124.2 appears to say flag is '1 if y of point > y of inverse point else 0' which I think just means
if y > x.
These slides (slide 15) by Julio Lopez and Ricardo Dahab appear to suggest my interpretation of the IEEE method is off (I think).
And this PDF - which I think is the standard reference - has yet another notation in section 2.3.3 part 2.2.2 that I do not understand.
Which of the above references represents the "standard" to handle this? And can someone please explain the proper/correct way to handle things; preferably from a programmer's perspective?