> On Mar 17, 2016, at 6:32 PM, Blumenthal, Uri - 0553 - MITLL <u...@ll.mit.edu> 
> wrote:
> 
> Oh, and I'd much prefer to stay at the EVP level, rather than invoke BIO 
> primitives for this task.

Well you can work with 
http://openssl.org/docs/manmaster/crypto/EC_KEY_key2buf.html
to extract EC public key octets.  If you want an ASN.1 encoded "SPKI" object 
(i.e. an
X509_PUBKEY in OpenSSL) then you can use

        X509_PUBKEY *pk = NULL;
        unsigned char *buf = NULL;
        EVP_PKEY *key;

        key = ... ; /* Get a keypair */

        if (X509_PUBKEY_set(&pk, key) <= 0) {
                /* error */
        }

        len = i2d_X509_PUBKEY(pk, &buf);
        if (len < 0 || buf == NULL) {
                /* error */
        }
        
        /* buf contains ASN.1-encoded SPKI, use it */

        OPENSSL_free(buf);
        X509_PUBKEY_free(pk);
        EVP_PKEY_free(key); /* If no longer needed */

A shorter version of the above is possible via i2d_PUBKEY() which
handles the creation, encoding and destruction of the intermediate
X509_PUBKEY:

  int i2d_PUBKEY(EVP_PKEY *a, unsigned char **pp)
  {
    X509_PUBKEY *xpk = NULL;
    int ret;
    if (!a)
        return 0;
    if (!X509_PUBKEY_set(&xpk, a))
        return 0;
    ret = i2d_X509_PUBKEY(xpk, pp);
    X509_PUBKEY_free(xpk);
    return ret;
  }


Looks like we need documentation for X509_PUBKEY_set() and friends...
Any volunteers?

X509_PUBKEY_free();
X509_PUBKEY_get();
X509_PUBKEY_get0();
X509_PUBKEY_get0_param();
X509_PUBKEY_new();
X509_PUBKEY_set();
X509_PUBKEY_set0_param();
d2i_DSA_PUBKEY_bio();
d2i_DSA_PUBKEY_fp();
d2i_EC_PUBKEY_bio();
d2i_EC_PUBKEY_fp();
d2i_PUBKEY_bio();
d2i_PUBKEY_fp();
d2i_RSA_PUBKEY_bio();
d2i_RSA_PUBKEY_fp();
i2d_DSA_PUBKEY_bio();
i2d_DSA_PUBKEY_fp();
i2d_EC_PUBKEY_bio();
i2d_EC_PUBKEY_fp();
i2d_PUBKEY_bio();
i2d_PUBKEY_fp();
i2d_RSA_PUBKEY_bio();
i2d_RSA_PUBKEY_fp();

-- 
        Viktor.
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