Cavalera Claudio Luigi
2008-Feb-05 15:22 UTC
[asterisk-users] is encrypted iax safe and secure?
Hello, I'm doing some research concerning iax encryption, I haven't find any clients (softphones or hardphones) which implement so I have not tested it yet. There was also this message on asterisk-security mailing list http://archives.free.net.ph/message/20070507.101933.222987b2.en.html which got no answers and this makes me think that this iax encryption is not much interesting for the community. Anyway, in iax specification there is this statement: "Only the data portion of the messages are encoded." Which are the consequences of this, is it true as stated on http://www.voip-info.org/wiki/view/IAX+encryption that "The calling/called numbers are still passed in the clear over encrypted IAX, so you are still vulnerable to traffic analysis." ? If it's true how to deal with this? Would you consider media payload encryption enough? Maybe it's better to just forget about iax encryption and consider some more general approach like using openvpn http://www.voip-info.org/wiki/view/IAX_OpenVPN ? This half-encrypted iax encryption doesn't make much sense to me, therefore I think there's probably something I'm missing/misunderstanding. Best Regards, Claudio Internet Email Confidentiality Footer ----------------------------------------------------------------------------------------------------- La presente comunicazione, con le informazioni in essa contenute e ogni documento o file allegato, e' rivolta unicamente alla/e persona/e cui e' indirizzata ed alle altre da questa autorizzata/e a riceverla. Se non siete i destinatari/autorizzati siete avvisati che qualsiasi azione, copia, comunicazione, divulgazione o simili basate sul contenuto di tali informazioni e' vietata e potrebbe essere contro la legge (art. 616 C.P., D.Lgs n. 196/2003 Codice in materia di protezione dei dati personali). Se avete ricevuto questa comunicazione per errore, vi preghiamo di darne immediata notizia al mittente e di distruggere il messaggio originale e ogni file allegato senza farne copia alcuna o riprodurne in alcun modo il contenuto. This e-mail and its attachments are intended for the addressee(s) only and are confidential and/or may contain legally privileged information. If you have received this message by mistake or are not one of the addressees above, you may take no action based on it, and you may not copy or show it to anyone; please reply to this e-mail and point out the error which has occurred. -----------------------------------------------------------------------------------------------------
On Tuesday 05 February 2008 09:22:29 Cavalera Claudio Luigi wrote:> Hello, > I'm doing some research concerning iax encryption, I haven't find any > clients (softphones or hardphones) which implement so I have not tested > it yet. > > There was also this message on asterisk-security mailing list > http://archives.free.net.ph/message/20070507.101933.222987b2.en.html > which got no answers and this makes me think that this iax encryption is > not much interesting for the community. > > Anyway, in iax specification there is this statement: > "Only the data portion of the messages are encoded." > > Which are the consequences of this, is it true as stated on > http://www.voip-info.org/wiki/view/IAX+encryption > that > "The calling/called numbers are still passed in the clear over encrypted > IAX, so you are still vulnerable to traffic analysis." > ? > > If it's true how to deal with this? > Would you consider media payload encryption enough? > Maybe it's better to just forget about iax encryption and consider some > more general approach like using openvpn > http://www.voip-info.org/wiki/view/IAX_OpenVPN ? > > This half-encrypted iax encryption doesn't make much sense to me, > therefore I think there's probably something I'm > missing/misunderstanding.Is it important for you to conceal that a call was made from abc to xyz on thus-and-such a date? Or do you merely need to conceal the content of a call? You can already do traffic analysis and figure out that a call occurred, just not what the endpoints are (even if you encrypted the entire link). The only way to get around that is to continuously send random garbage through the pipe at the same rate and consistency as would occur with a real IAX2 call. And the endpoints are only as specific as the systems on either end choose to make them. If you used some system of src/dst obfuscation, you could conceal even that information, though repeated calls to various destinations could still be paired and correlated. IAX2 encryption is designed to obscure the same information as is obscured when you encrypt a call over the PSTN -- the content is protected, but the existence of such a call is not. Remember that a potential attacker will always choose the weakest link, and will probably attack the audio stream at a different location, if she cannot listen to the IP stream directly (such as a true wiretap on an analog endpoint or breaking into one of the two machines involved in the encryption). The idea is to make the IAX2 link unattractive as a potential target of wiretapping (whereas before it would have been the most obvious choice), thus forcing the attacker to choose a different attack scenario. -- Tilghman