Re: [AVT] SRTP Question

[Mark Baugher <mbaugher at cisco.com>]

At 08:05 AM 7/16/2004, Steffen Fries wrote:
> Hi,
>
> I've got another question to SRTP ;-)
>
> Within RFC3711 it is mentioned in section 3.3.1:
> "...  After that number of SRTP packets have been sent
> with a given (master or session) key, the sender MUST NOT send
> any more packets with that key. ..."
>
> Further, section 8.1.1 reads:
> "... The default values for the <From, To> are "from the first
> observed packet" and "until further notice".  However, the
> maximum limit of SRTP/SRTCP packets that are sent under each
> given master/session key (Section 9.2) MUST NOT be exceeded...."
>
> Does this mean, that both sender and receiver have to ensure,
> that the maximum number of packets encrypted with the same key
> is not exceeded? If yes, is the recommendation, that the
> receiver discards the packets that are received after the key
> usage has reached the maximum limit?

This probably should have been spelled out in RFC 3711 because there are 
number of alternative actions such as discard the packets, stop receiving 
the stream in the case of multicast, leave the session regardless of how 
many senders are securely sending when one sender violates the key lifetime.

I would say that the session is no longer secure and the receiver should 
leave the session and log the condition.

Thankfully, this is a very unlikely event in the forseeable future.

Mark


> Ciao
>         Steffen
>
>
>
> _______________________________________________
> Audio/Video Transport Working Group
> avt at ietf.org
> https://www1.ietf.org/mailman/listinfo/avt



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