31 Jul
2014
31 Jul
'14
2:38 p.m.
Thanks for good insight in to this topic.
As mentioned in my first email, there are a number of reasons for trying
out custom encryption schemes. Low-end android devices is just one of them.
There is a huge market for low-end android devices in south and south east
Asia for example, where over 35% of world population lives. The people
there are poor and don't have much understanding of latest cutting edge
smart devices and related technologies. Big brands like Apple, Samsung,
Nokia etc. are virtually non-existent or have so high price that people
simply can't afford them. So cheap Chinese and Indian cell phones which
barely run Android are considered "smart phones" and are very popular here.
Using SSL, TLS, DTLS etc. are nightmare on these devices.
The other reasons to develop and try out custom encryption algorithms are
voip blockage by GSM providers in various Middle Eastern and European
counties,
http://www.linphone.org/news/11/26/Linphone-over-3G.html
http://xerocrypt.wordpress.com/2012/07/06/inspecting-your-packets/
http://www.telecomrecorder.com/world-premium-telecom/pak-telecom-authority/…
And the rogue agencies of evil empires,
http://en.wikipedia.org/wiki/Five_Eyes
http://en.wikipedia.org/wiki/PRISM_%28surveillance_program%29
http://en.wikipedia.org/wiki/Booz_Allen_Hamilton#Activities_in_foreign_coun…
http://www.itv.com/news/update/2013-09-06/report-us-and-uk-agencies-cracked…
Nearly all encryption algorithms are defined and advocated by US and UK
intelligence agencies and it is quite obviously possible that they either
have crack or backdoors into them. So, we can't blindly trust them anymore
and should look into defining our own algorithms and security standards.
Just to note, i don't claim that ITV or any other custom encryption
discussed here can or would resolve all these problems. The main focus is
on trying something new and out of the box to improve the voip and network
security conditions. I find Kamailio as open source SIP server and doubango
as open source SIP SDK as best platforms for these efforts and
experimentation.
Thank you.
On Thu, Jul 31, 2014 at 2:08 PM, Daniel Tryba <daniel(a)pocos.nl> wrote:
[remove dev from cc]
The key purpose of ITV encryption is to avoid
making a pattern of any
sort.
The pattern is in SIP itself, regardless of encryption.
-OPTIONS keepalives and response at regular intervals of nearly fixed size.
-INVITE and its predictable responses of nearly fixed sizes per type
followed
by a steady stream of upd on random ports with the same bandwidth flowing
both
sides.
Unless this random utp traffic is encrypted it is obvious you are using rtp
with something like SIP. Even if it is encrypted the symmetric streams give
away clues. A simple xor isn't enough, silences will result in the same
pattern.
Daniel(-Constanting) already suggested interval randomizing (which is to be
applied to any response) and padding of all data.
But I wouldn't trust any non vetted encryption scheme, it is much easier to
fix timing/padding with the standard tls scheme. Which brings me to the
question: what kind of device on the market capable of running apps isn't
fast
enough for TLS?
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