[VOIPSEC] Secure Real-time Transport Protocol (SRTP)

[Jeremy George]

   Will HIPAA requirements drive encrypted voice/IM/video ?

- Jeremy


On Wed, 23 Mar 2005, Brian Raymond wrote:

> Date: Wed, 23 Mar 2005 20:41:09 -0500
> From: Brian Raymond <brian-lists at dataline.com>
> To: kapnet at mindspring.com, VoIPsec <voipsec at voipsa.org>
> Subject: Re: [VOIPSEC] Secure Real-time Transport Protocol (SRTP)
> 
> I had a couple of comments for the thread.
>
> Avaya has always supported H.235 for security on H.323 calls so I would
> imagine they are still doing the same now. I'm not sure however which
> profile they are working with these days. There are a number of security
> profiles (Annexes) specifying different algorithms for encryption and key
> management. Related to MIKEY is H.235 Annex G, which is MIKEY and SRTP for
> transport. Signaling of H.225 is generally encrypted via TLS or IPSEC, at
> least what I've seen. Key exchange for media is over H.245 however the
> method is specific to the profile.
>
> I agree with some of the other members that the main reason there isn't a
> focus on application level security is that the market just hasn't demanded
> it. That's starting to shift now but as someone who has previously worked
> for a commercial vendor of a number of H.323/SIP products we never saw a
> real demand from customers for that type of support. Any customers who
> required security implemented it at layer 2/3 using some sort of VPN. This
> was generally not an issue because that type of system was already in place
> most of the time and provided much greater endpoint flexibility.
>
> I have supported the government sector for a few years now and even in what
> are considered high(er) security environments with arguably critical data to
> protect transport encryption was never a real issue. Again this is all
> changing now and I'm seeing a number of splintered implementations popping
> up. Most people I have talked to are only familiar with their specific
> application's protocol implementation and when designing a solution aren't
> concerned about interoperability. This is actually quite interesting because
> these same applications are using standards to foster interoperability.
>
>
> - Brian
>
>
>
> On 3/23/05 6:05 PM, "Ken Peterson" <kapnet at mindspring.com> wrote:
>
>> Ian,
>> 
>> The only major vendor doing official SRTP, to my knowledge, is Cisco in
>> release 4.1 of their CallManager, which was just released last fall. The
>> signaling channel is protected via TLS - both phone and CM server have
>> certificates to authenticate each other. Over this "always-up" control
>> channel, they speak Cisco's proprietary Skinny protocol. During call setup,
>> the CM sends a shared symmetric key to both IP endpoints. The endpoints 
>> then
>> speak SRTP using AES-128 encryption and SHA-1 HMAC.
>> 
>> I know of one major government organization that is implementing this
>> solution as we speak. They are the rare exception, however.
>> 
>> Avaya's solution is supposed perform a similar process, but using H.323.
>> Their release date was pushed back last time I checked (was supposed to be
>> out now.) Currently Avaya is using 102-bit AEA (Avaya Encryption Algorithm)
>> between phones... I assume the voice is encapsulated in SRTP, but I could 
>> be
>> wrong... anyone else know? The key exchange (again Im not confident in 
>> this,
>> due to Avaya's lack of documentation) should be a Diffie-Helman exchange
>> over the H.225 control channel. Is that D-H exchange authenticated to avoid
>> MITM attacks? I would hope so, but I've seen no evidence to support that.
>> 
>> Cheers,
>>  Ken
>> 
>> ************************************************************************
>> *                             *
>> *  Ken Peterson, CCIE 4297 *  Cisco Certified Security Professional
>> *  PacketBrain, Inc.          *  Cisco IP Telephony Support Specialist
>> *  Cary, NC 27511             *  Cisco Content Networking Specialist
>> *                             *
>> ************************************************************************
>> 
>> 
>> 
>> -----Original Message-----
>> From: Voipsec-bounces at voipsa.org [mailto:Voipsec-bounces at voipsa.org]On
>> Behalf Of Brian Rosen
>> Sent: Wednesday, March 23, 2005 4:44 PM
>> To: Ian.Cuthbertson at nokia.com; Voipsec at voipsa.org
>> Subject: RE: [VOIPSEC] Secure Real-time Transport Protocol (SRTP)
>> 
>> 
>> There is not much deployment yet.
>> One of the reasons is confusion on key exchanges.
>> Another is there is not (yet) much demand.
>> 
>> Brian
>> 
>>> -----Original Message-----
>>> From: Voipsec-bounces at voipsa.org [mailto:Voipsec-bounces at voipsa.org] On
>>> Behalf Of Ian.Cuthbertson at nokia.com
>>> Sent: Wednesday, March 23, 2005 12:10 PM
>>> To: Voipsec at voipsa.org
>>> Subject: [VOIPSEC] Secure Real-time Transport Protocol (SRTP)
>>> 
>>> Hi,
>>> 
>>> Does anyone have a take on how widely deployed SRTP is in the real
>>> world? Are all vendors offing solutions which include this (gateway,
>>> handset etc)? Which key exchange methods do they support?
>>> 
>>> Thanks, Ian
>>> 
>>> 
>>> 
>>> _______________________________________________
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>>> Voipsec at voipsa.org
>>> http://voipsa.org/mailman/listinfo/voipsec_voipsa.org
>>> 
>> 
>> 
>> 
>> 
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>> 
>> 
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>
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