Subject: Re: FUD about CGD and GBDE
To: None <>
From: Poul-Henning Kamp <>
List: tech-security
Date: 03/07/2005 17:49:50
In message <>, writes:
>> I also believe that it would be beneficial to implement regular rewriting
>> of randomly picked lock sector(s) at random times during a user specified
>> interval (up to x rewrites within n seconds) in order to further obscure
>> the write pattern and provide additional protection for lock sectors.
>> ALeine
>I agree. I would also add random reads (or specially designed, combined
>random reads and writes) to make traffic analysis and differential attacks
>a real PITA for the hacker (although this idea may not be very effective
>against a highly motivated and determined attacker, such as some government,
>for instance).

If you want to do something like this, you want to do sectorrenaming
and journaling since that means you can only see that something
was written but not what it was that was written.

The performance cost can be considerable and the complexity formidable.
There are incredibly many cornercases to handle.

>BTW, PHK, why did you choose the scheme of encrypting offsets of lock
>sectors with part of key material and storing them somewhere, instead
>of just using part of the key material itself to determine the offsets?

Because if I used part of the key material you would have to change
the location of the lock sectors when you changed the key material.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.