Re: [OPSEC] [tcpm] draft-gont-tcp-security

[Joe Touch <touch at ISI.EDU>]

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Fernando Gont wrote:
...
>> That said there's also some question as what sort of general
>> recommendations about hardening tcp would actually be consider
>> acceptable (in narrow use cases a lot more of them may well be).
>>
>> 	The diligent blacksmith knows that hardening a tool also
>> 	makes it more brittle...
> 
> This is a nice quote, but... I'd like examples. e.g., start discussing
> about which specific hardening proposal makes TCP more brittle.

1) any security mechanism that increases complexity - of actions, state,
or message exchanges - any of which increases the potential for
implementation error

2) any security mechanism that has false positives, i.e., that discards
messages deemed a security threat when they were sent for legitimate reasons

#1 includes basically everything, from TCP MD5 (and TCP-AO) to tcpsecure
and ICMP filtering

#2 includes anything with nonzero false positives, such as tcpsecure and
ICMP filtering

I.e., AFAICT, *everything* that makes TCP more secure also makes it
brittle, by definition (ditto for metal hardening, FWIW). The key issue
is "when/where is the benefit worth the cost".

Joe
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