DTLS: Use ECDSA key

plugins/ice/src/dtls_srtp.vala

@@ -76,7 +76,7 @@ public class Handler {
         int err = 0;
 
         X509.PrivateKey private_key = X509.PrivateKey.create();
-        err = private_key.generate(PKAlgorithm.RSA, 2048);
+        err = private_key.generate(PKAlgorithm.ECDSA, 256);
         throw_if_error(err);
 
         var start_time = new DateTime.now_local().add_days(1);

plugins/ice/vapi/gnutls.vapi

@@ -221,7 +221,8 @@ namespace GnuTLS {
     public enum PKAlgorithm {
         UNKNOWN,
         RSA,
-        DSA;
+        DSA,
+        ECDSA;
     }
 
     [CCode (cname = "gnutls_digest_algorithm_t", cprefix = "GNUTLS_DIG_", has_type_id = false)]