On 09/01/15 10:55, Christian Weber wrote: > Am 09.01.2015 um 01:11 schrieb Matt Caswell: On 09/01/15 00:05, > Christian Weber wrote: >>> Thanks Matt, i just assumed the BIGNUMs were the coordinates without >>> any projection - obviously that assumption was wrong - mislead by the >>> funtions name. >>> >> What interests me is to how you accessed the BIGNUMs in the first place! >> The EC_POINT structure is opaque and is defined in an internal header >> file!! Applications shouldn't be reaching into those. >> >> Matt > Actually i imported the internal header so the structure was known. I > marked the import as HACK to access exactly that EC_POINT structure. The > hack was carried out because of the lack of knowledge about how to > access the public key. > > I yust did not understand the intention for hiding the EC_POINT > structure and didn't find information about how to access the coordinate > values which i need to compare with coordinates from other sources (XML > Dsig, Element <ds:KeyValue>) or placing them elsewhere. > > So could you please give a hint or a pointer to where the intended > access can be found? All access is via the EC_POINT_* functions which are described here: https://www.openssl.org/docs/crypto/EC_POINT_new.html and here: https://www.openssl.org/docs/crypto/EC_POINT_add.html > > BTW: How does one find out which type of ECC is being used (binary or > prime)? Use the function EC_METHOD_get_field_type described here: https://www.openssl.org/docs/crypto/EC_GFp_simple_method.html > BTW2: Which compact representation of any public key would you recommend > (for program internal comparisons)? I wouldn't worry about the internal representation at all. If you have the co-ordinates of a point you want to compare against then construct the point using EC_POINT_new, and set its co-ords using one of the various functions for doing so. Then use EC_POINT_cmp. > > Surely i will ban the internal header from my sources as they are not > neccessary. Please do! They are internal for a reason, and may change without notice. Matt
