PEM_read_PrivateKey
pktmp = PEM_read_PrivateKey(fp, NULL, cb, u);
pktmp = PEM_read_PrivateKey(fp, NULL, cb, u);
pktmp = PEM_read_PrivateKey(fp, NULL, cb, u);
key = PEM_read_PrivateKey(fp, NULL, tls_password_cb, password);
key = PEM_read_PrivateKey(keyfp, NULL, NULL, NULL);