On 3 September 2013 15:16, Jonas Andersson <jonasanderssonm...@gmail.com> wrote: > Hi all, > > Is there a way to verify a signature with ECDSA_do_verify having only the > x-coordinate (in public key) available?
Are you sure you *only* have the x-coord and not a point in compressed format? The difference being that with compressed format you get an octet at the front specifying which of the two possible y values to use (the y bit) followed by the full octets for the x coordinate. If you have it in compressed format as an octet string there are functions to load it. You need to make sure that the point conversion form for the curve is POINT_CONVERSION_COMPRESSED. You can set this using EC_GROUP_set_point_conversion_form (not sure off the top of my head what the default is for this). You can then load your compressed point using EC_POINT_oct2point. Alternatively you can use EC_POINT_set_compressed_coordinates_GFp or EC_POINT_set_compressed_coordinates_GF2m (for prime curves or binary curves as appropriate). Hope that helps, Matt ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager majord...@openssl.org
