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Re: Skype vulnerability or feature
From: Nicolas RUFF <nicolas.ruff () gmail com>
Date: Wed, 02 Aug 2006 10:00:39 +0200

I was fiddling a little bit with Skype when I discovered that I could
login at the same time from two different terminals unlike other
messengers such as MSN. In such a scenario if someone gets hold of
your skype identity you would never know and he might just successfuly
abuse your account again and again.

-> Multiple login seems to be a known feature:
http://en.wikipedia.org/wiki/Skype
"Skype currently permits multiple concurrent logins"

-> If you want to evaluate the possibility of a replay attack, have a
look at the authentication scheme:
http://www.secdev.org/conf/skype_BHEU06.handout.pdf

If you want to go farther than authentication (e.g. listening at
conversations), you will need to get access to the original session keys
from Skype process memory ...

Anyway, this attack is unpractical unless you have an Open Source Skype
client :)

Regards,
- Nicolas RUFF


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