Use elliptic curve cryptography based DTLS Key Establishment Protocol

app/src/main/assets/config

@@ -52,3 +52,5 @@ opus_sprop_stereo no
 ice_turn no
 ice_nomination regular
 zrtp_hash yes
+dtls_srtp_use_ec prime256v1
+

app/src/main/kotlin/com/tutpro/baresip/Config.kt

@@ -106,6 +106,9 @@ object Config {
             BaresipService.contactsMode = "baresip"
         }
 
+        if (!config.contains("dtls_srtp_use_ec"))
+            config = "${config}dtls_srtp_use_ec prime256v1\n"
+
         Utils.putFileContents(configPath, config.toByteArray())
         BaresipService.isConfigInitialized = true
         Log.i(TAG, "Initialized config to '$config'")