ossl_x25519_public_from_private
ossl_x25519_public_from_private(key->pubkey, key->privkey);
void ossl_x25519_public_from_private(uint8_t out_public_value[32],
ossl_x25519_public_from_private(key->pubkey, privkey);
ossl_x25519_public_from_private(pub, ecx->privkey);