Re: [TLS] Selfie attack

Christian Huitema <huitema@huitema.net> Tue, 08 October 2019 18:51 UTC

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To: Christopher Wood <caw@heapingbits.net>, Mohit Sethi M <mohit.m.sethi@ericsson.com>, "TLS@ietf.org" <tls@ietf.org>
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From: Christian Huitema <huitema@huitema.net>
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Date: Tue, 8 Oct 2019 11:51:00 -0700
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Subject: Re: [TLS] Selfie attack
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On 10/8/2019 9:46 AM, Christopher Wood wrote:

> On Tue, Oct 8, 2019, at 2:55 AM, Mohit Sethi M wrote:
>>  
>> Hi Chris,
>>
>> For the benefit of the list, let me summarize that the selfie attack is 
>> only relevant where multiple parties share the same PSK and use the 
>> same PSK for outgoing and incoming connections. These situations are 
>> rather rare, but I accept that TLS is widely used (and sometimes 
>> misused) in many places.


I may be getting old but the way Mohit writes it, it seems that the
attack happens when the security of a group relies on a secret shared by
all members of the group, and can then be compromised when one of the
group members misbehaves. How is that a new threat? If groups are
defined by a shared secret, then corruption of a group member reveals
that shared secret to the attacker and open the path for all kinds of
exploitation. In what sense is the "selfie" attack different from that
generic threat?

-- Christian Huitema