Dear Ken, One way to accomplish this is something along the lines of
EC_POINT *EC_KEY_get0_public_key(const EC_KEY *); where EC_KEY is the key structure, returning the point as an EC_POINT structure, followed by int EC_POINT_get_affine_coordinates_GFp(const EC_GROUP *, const EC_POINT *, BIGNUM *x, BIGNUM *y, BN_CTX *); where EC_GROUP is setup for P-521 (have a look at EC_GROUP_new_by_curve_name), EC_POINT is the public key from the previous call; it dumps the coordinates to x and y, where you can use BN_bn2bin or whatever you like. You'd reverse it with int EC_POINT_set_affine_coordinates_GFp(const EC_GROUP *, EC_POINT *, const BIGNUM *x, const BIGNUM *y, BN_CTX *); followed by int EC_KEY_set_public_key(EC_KEY *, const EC_POINT *); While this is the manual way to do it that you've asked for, there are a few caveats that can affect security so if possible I'd consider standard (ANSI? P1363?) methods like EC_POINT_point2bn and so on. Those also easily allow point compression if that's needed. In general, poke around in include/openssl/ec.h and there is lots of useful functionality, although not as much documentation. Sincerely, Billy On Fri, Jul 15, 2011 at 10:54 AM, Kenneth Goldman <kgold...@us.ibm.com> wrote: > I have to extract a binary (unsigned char *) representation of a public key > from an ECDSA openssl key structure. Later, I want to use that binary to > reconstruct an openssl public key structure that I can use to verify a > signature. The curve is fixed - P521. > > I don't need any certificates, just a public key that I can embed in the > verifier. > > Can someone point me toward sample code? Or, can someone give me some > hints? > > -- > Ken Goldman kg...@watson.ibm.com > 914-784-7646 (863-7646) > ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager majord...@openssl.org
