Yeah, of course, sorry for the typo. I’ve already found a solution that seems to be working by using EVP_PKEY_get_raw_public_key() for these types of curves. I was confused why it’s not working with EC_KEY interfaces though it’s type of elliptic curve. Then I found somewhere that it’s implemented outside the context of EC. It’s not clear to me why but I believe there’s a good reason for it. Anyway, thanks for your answer!
Regards Matt On 18. 11. 2022, at 17:13, Kyle Hamilton <aerow...@gmail.com> wrote: X25519? On Mon, Nov 14, 2022, 05:23 ORNEST Matej - Contractor via openssl-users <openssl-users@openssl.org<mailto:openssl-users@openssl.org>> wrote: Hi all, I need to implement support for X52219/X448 for DH key exchange (and Ed52219/Ed448 for DSA) elliptic curves in our project. I need to export public key for DH exchange in form of DER encoded chunk in form tag+X-coordinate+Y-coordinate. Thus I need to get EC_POINT from EVP_PKEY and encode it as needed. I understand that those key types differs from EC types in way that I need just X coordinate and a flag bit to reconstruct the key, but still, how do I get the X coordinate? My solution works for all other EC types such as SecpX and Brainpool families, but not for X52219/X448 keys and I do not completely understand why. Specifically when I decode public key previously encoded with i2d_PUBKEY() to EVP_PEKY and try to get EC_KEY by calling EVP_PKEY_get0_EC_KEY(), it returns NULL and issues an error that it’s not an EC key… I’m using following code: EVP_PKEY *key = … // Decode from DER encoded public key if(key != nil) { EC_KEY *ecKey = EVP_PKEY_get0_EC_KEY(key); /// When X52219 or X448 key is passed, ecKey is NULL if(ecKey != NULL) { const EC_POINT *point = EC_KEY_get0_public_key(ecKey); const EC_GROUP *group = EC_KEY_get0_group(ecKey); if(point != NULL && group != NULL) { BIGNUM *bnX = BN_new(); BIGNUM *bnY = BN_new(); if(EC_POINT_get_affine_coordinates(group, point, bnX, bnY, NULL)) { char *hexX = BN_bn2hex(bnX); char *hexY = BN_bn2hex(bnY); // Convert to custom data structures … } BN_free(bnX); BN_free(bnY); } } } Is there any way how to export those key types in desired format? I’m using OpenSSL version 1.1.1q. Thank you very much for any hint Matt
