title: How to get the length of EC key in a EC certificate?
body: <p>I have a EC certficate(the signature algorithm is ECDSA),I want to know the length of EC key using openssl api.
  Now, I can get the EC_KEY structure from the certificate,but I don't know  which elem in EC_KEY is the length of key and how to get it.</p>
  
  <p>The following is the structure of EC_KEY:</p>
  
  <pre><code>struct ec_key_st {
      int version;
      EC_GROUP *group;// used to represent the definition of an elliptic curve
      EC_POINT *pub_key;//used to store the points on the elliptic curve
      BIGNUM   *priv_key;
      unsigned int enc_flag;
      point_conversion_form_t conv_form;
      int     references;
      int flags;
      EC_EXTRA_DATA *method_data;
  } /* EC_KEY */;
  </code></pre>
  
  <p>Please help!</p>