Subject: [MMUSIC] SDP encryption key

From: [email-masked]
Date: Wed, 29 May 2002 14:00:19 +0300 (EEST)

Hello all,
What is the meaning of encryption key?
1. When offering a key, this means that the offerer will use
the key ONLY for encryption. The answerer will provide
its OWN encryption key which the offerer has to use to decrypt
the incoming data.

OR
2. When offering a key, this means that the offerer will use
the key BOTH for encryption and decryption. The answerer
HAS to respond with the SAME encryption key from the offer
and it will use it BOTH for encryption and decryption.

If 2. is correct, what happens when the answerer respons with
other key?

If 1. is correct, then the encryption key characterizes the
OUTGOING media stream. In this case what would be the answer
to an offer for a send-only encrypted media stream like:
m=...............
a=send-only
k=base64:key1 ?

An answer like:
m=.....
a=recv-only
k=base64:key2
is not consistent even if key1=key2, because the answerer
will not send any media !!!
An answer like:
m=....
a=recv-only
is consistent, but what if the answerer does not support
encryption? It should signall through a SIP error code
that it does not support/want encryption?

Much more simple would be 2. (SYMETRIC KEYS).
If some terminal support encryption, then it must
answer with the proposed key. Otherwise, it must not
include the 'k=' line.

Please indicate which mode is correct.
1. or 2. ?
Thank you in advance,
Dan Firac,
Software Engineer,
Redline Communications, Romania.
+4093260623

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