Re: [rtcweb] SRTP not mandatory-to-use
Eric Rescorla <ekr@rtfm.com> Thu, 15 December 2011 01:14 UTC
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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 15 Dec 2011 06:43:53 +0530
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To: Xavier Marjou <xavier.marjou@gmail.com>
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Subject: Re: [rtcweb] SRTP not mandatory-to-use
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On Wed, Dec 14, 2011 at 8:11 PM, Xavier Marjou <xavier.marjou@gmail.com> wrote: > On Wed, Dec 14, 2011 at 11:32 AM, Eric Rescorla <ekr@rtfm.com> wrote: >> >> On Wed, Dec 14, 2011 at 3:18 PM, Xavier Marjou <xavier.marjou@gmail.com> wrote: >> > Hi, >> > >> > >> > During the last IETF meeting, there seemed to be many people willing to have >> > SRTP mandatory-to-use in the browser. However, I would like again to >> > underline that in some contexts, it is rather desirable to deactivate, via >> > the WebRTC API, the use of SRTP in order not to encrypt/decrypt at multiple >> > layers. >> > >> > >> > This may be the case in the following example: a company wants to use WebRTC >> > for communications between its co-workers only; the web server and the >> > script using WebRTC API are located on the VPN. In such a case, there is no >> > need to use SRTP. The VPN already provides encryption when needed. If >> > co-workers want to remotely access the VPN, an IPsec tool can already >> > provide the encryption. Furthermore, if they want to remotely access the VPN >> > via a 3G network, there will be encryption at layer 2 using AKA, then IPsec >> > at layer 3, and again at SRTP level if mandatory-to-use. >> >> I don't understand why this makes SRTP undesirable. What scarce >> resource are you conserving >> here by not using SRTP? As has been noted a number of times, the cost >> of the crypto on >> the endpoints is generally not significant. > > Is there any scientific reference comparing the performances (cpu) of > a SRTP communication vs an RTP communication on a smartphone device, > or on an interworking network server? The feedback I have is that SRTP > overhead is significant, at least on interworking network servers > handling several calls in parallel. One example is > http://trac.pjsip.org/repos/wiki/PJMEDIA-MIPS which gives figures, > perhaps non-optimized, but figures anyway: > > > 00:59:38.531 os_core_unix.c pjlib 0.9.0-trunk for POSIX initialized > MIPS test, with CPU=180Mhz, 198.0 MIPS > Clock Item Time CPU MIPS > Rate (usec) (%) > 8KHz codec encode/decode - L16/8000/1 1704 0.170 0.34 > 8KHz stream TX/RX - G.711 6786 0.679 1.34 > 8KHz stream TX/RX - G.711 SRTP 32bit 21688 2.169 4.29 > 8KHz stream TX/RX - G.711 SRTP 32bit +auth 33501 3.350 6.63 > 8KHz stream TX/RX - G.711 SRTP 80bit 21725 2.172 4.30 > 8KHz stream TX/RX - G.711 SRTP 80bit +auth 33551 3.355 6.64 I'm not sure why you chose this particular platform. It doesn't seem to really be representative of what we are targeting. Regardless, on desktop class machines or modern smartphones (e.g. iPhone) the crypto shouldn't represent a particularly large fraction of the load. For instance, a macbook air can do something like 128 MB/s on a single core. >> Moreover, it's not obvious that even in this setting SRTP doesn't add security >> benefit. Why are you assuming that I want everyone on the same LAN >> as me to be able to listen to my calls, even if they are my co-workers? >> > > Adding more security like SRTP certainly adds more confidence and > probabilities that the call is more secure. However, as most of you > know, there is no guarantee that nobody can listen to your calls even > with SRTP. The web server is in the path of the webrtc media IP and > port advertised by the browser of the users; It thus has the > possibility to modify these parameters and direct a user's browser to > communicate towards an SRTP-to-SRTP gateway instead of the remote > called user. The communication between the two users is made of 2 SRTP > links, with an unencrypted access possible at the SRTP gateway. (1) I would encourage you to read draft-ietf-rtcweb-security-01, which considers this and other related issues in detail. (2) I don't really see the relevance of this point to your example, which was about people in allegedly secure network environments. My point is that just because you are behind a firewall doesn't mean that you want everyone behind the firewall to have access to your communications. This seems orthogonal to the question of whether you trust the media server. -Ekr
- Re: [rtcweb] SRTP not mandatory-to-use Xavier Marjou
- [rtcweb] SRTP not mandatory-to-use Xavier Marjou
- Re: [rtcweb] SRTP not mandatory-to-use Eric Rescorla
- Re: [rtcweb] SRTP not mandatory-to-use Iñaki Baz Castillo
- Re: [rtcweb] SRTP not mandatory-to-use Markus.Isomaki
- Re: [rtcweb] SRTP not mandatory-to-use Xavier Marjou
- Re: [rtcweb] SRTP not mandatory-to-use Igor Faynberg
- Re: [rtcweb] SRTP not mandatory-to-use Roy, Radhika R USA CIV (US)
- Re: [rtcweb] SRTP not mandatory-to-use Eric Rescorla
- Re: [rtcweb] SRTP not mandatory-to-use Harald Alvestrand
- Re: [rtcweb] SRTP not mandatory-to-use Randell Jesup
- Re: [rtcweb] SRTP not mandatory-to-use Markus.Isomaki
- Re: [rtcweb] SRTP not mandatory-to-use Randell Jesup
- Re: [rtcweb] SRTP not mandatory-to-use Justin Uberti
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Ted Hardie
- Re: [rtcweb] SRTP not mandatory-to-use Eric Rescorla
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Eric Rescorla
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Randell Jesup
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Alan Johnston
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Ted Hardie
- Re: [rtcweb] SRTP not mandatory-to-use Ted Hardie
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Justin Uberti
- Re: [rtcweb] SRTP not mandatory-to-use Olle E. Johansson
- Re: [rtcweb] SRTP not mandatory-to-use Randell Jesup
- Re: [rtcweb] SRTP not mandatory-to-use Stefan Hakansson LK
- Re: [rtcweb] SRTP not mandatory-to-use Ravindran, Parthasarathi
- Re: [rtcweb] SRTP not mandatory-to-use Harald Alvestrand
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Cullen Jennings
- Re: [rtcweb] SRTP not mandatory-to-use Kevin P. Fleming
- Re: [rtcweb] SRTP not mandatory-to-use Alan Johnston
- Re: [rtcweb] SRTP not mandatory-to-use Ted Hardie
- Re: [rtcweb] SRTP not mandatory-to-use Randell Jesup
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Ravindran, Parthasarathi
- Re: [rtcweb] SRTP not mandatory-to-use Spencer Dawkins
- Re: [rtcweb] SRTP not mandatory-to-use Ravindran, Parthasarathi
- Re: [rtcweb] SRTP not mandatory-to-use Muthu Arul Mozhi Perumal (mperumal)
- Re: [rtcweb] SRTP not mandatory-to-use Eric Rescorla
- Re: [rtcweb] SRTP not mandatory-to-use Ravindran, Parthasarathi
- Re: [rtcweb] SRTP not mandatory-to-use Iñaki Baz Castillo
- Re: [rtcweb] SRTP not mandatory-to-use Ravindran, Parthasarathi
- Re: [rtcweb] SRTP not mandatory-to-use Iñaki Baz Castillo
- Re: [rtcweb] SRTP not mandatory-to-use Ravindran, Parthasarathi
- Re: [rtcweb] SRTP not mandatory-to-use Justin Uberti
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Randell Jesup
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Eric Rescorla
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Randell Jesup
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Bernard Aboba
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Justin Uberti
- Re: [rtcweb] SRTP not mandatory-to-use Justin Uberti
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Eric Rescorla
- Re: [rtcweb] SRTP not mandatory-to-use Ravindran, Parthasarathi
- [rtcweb] JSEP draft query [was RE: SRTP not manda… Ravindran, Parthasarathi
- Re: [rtcweb] SRTP not mandatory-to-use Cullen Jennings
- [rtcweb] state of libsrtp maintenance? (Re: SRTP … Harald Alvestrand
- Re: [rtcweb] JSEP draft query [was RE: SRTP not m… Harald Alvestrand
- Re: [rtcweb] SRTP DTLS - SIPit Olle E. Johansson
- Re: [rtcweb] JSEP draft query [was RE: SRTP not m… Ravindran, Parthasarathi
- Re: [rtcweb] SRTP not mandatory-to-use Ravindran, Parthasarathi
- Re: [rtcweb] state of libsrtp maintenance? (Re: S… Roman Shpount
- Re: [rtcweb] state of libsrtp maintenance? (Re: S… Eric Rescorla
- Re: [rtcweb] SRTP DTLS - SIPit Eric Rescorla
- Re: [rtcweb] SRTP DTLS - SIPit Hannes Tschofenig
- Re: [rtcweb] state of libsrtp maintenance? (Re: S… Roman Shpount
- Re: [rtcweb] SRTP not mandatory-to-use Oscar Ohlsson
- Re: [rtcweb] state of libsrtp maintenance? (Re: S… Randell Jesup
- Re: [rtcweb] SRTP not mandatory-to-use Ted Hardie
- Re: [rtcweb] SRTP not mandatory-to-use Eric Rescorla
- Re: [rtcweb] SRTP not mandatory-to-use Harald Alvestrand
- Re: [rtcweb] SRTP not mandatory-to-use Oscar Ohlsson
- Re: [rtcweb] Security analysis of RTCWEB Bernard Aboba
- Re: [rtcweb] Security analysis of RTCWEB Eric Rescorla
- Re: [rtcweb] Security analysis of RTCWEB Igor Faynberg
- Re: [rtcweb] Security analysis of RTCWEB Bernard Aboba
- Re: [rtcweb] state of libsrtp maintenance? (Re: S… Cullen Jennings