sfs8 pt1

[Charles Lindsey]

On Tue, 23 Sep 2008 15:25:54 +0100, Mark Lomas <tmalomas@gmail.com> wrote:

> Playing Devil's Advocate:
>
> By configuring the server to accept more than one protocol the  
> administrator
> implied that each of those protocols satisfies the relevant security  
> policy.
> In such a case the server ought to choose the least* secure protocol
> acceptable to the client.
>
> * Unless the more secure protocol has no additional cost whatsoever.
>
> If perfect forward secrecy is a requirement this can be achieved by
> disabling the protocols that don't provide it. Consequently, the server's
> behaviour is not at fault, although the server administrator may be at  
> fault
> for permitting less secure protocols.

I don't see that as a valid argument. The reason that a server chooses to  
accept some less secure protocols as well as the most secure ones would be  
that some ancient browsers might only offer the less secure ones, and  
better to use those than nothing at all.

I doubt that using Diffie Helleman, where available, would have  
significant costs over the others (it is just a negotiation that takes  
place once, at the start of a connection).

> 2008/9/23 Charles Lindsey <chl@clerew.man.ac.uk>
>

>> Well, in that case, I would regard it as the server's fault, since it  
>> ought
>> to consider all of the offerings and choose the most secure, according  
>> to
>> some internal ranking which it should have.

-- 
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