Date: Wed, 15 Oct 1997 11:10:38 +0930 From: Mike Smith <mike@smith.net.au> To: "Christopher G. Petrilli" <petrilli@amber.org> Cc: security@FreeBSD.ORG Subject: Re: C2 Trusted FreeBSD? Message-ID: <199710150140.LAA00804@word.smith.net.au> In-Reply-To: Your message of "Tue, 14 Oct 1997 21:13:53 -0400." <Pine.BSF.3.96.971014211120.2865J-100000@dworkin.amber.org>
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(Followups to this should probably only go to -chat) > On Wed, 15 Oct 1997, Mike Smith wrote: > > > And besides, zero-filling memory isn't sufficient, it has to be > > > overwritten a number of times to make sure now residual information can > > > be obtained. These standards date back to core and even mercury-wire > > > memory. Yes, I've actually worked with computers that feature *both* in > > > my career. ;^) > > > > If you can suggest how one goes about obtaining "residual" information > > from a saturated logic device in a synchronous memory subsystem, I'd be > > very interested in hearing it. > > > > Or is this more specification paranoia? > > I will note that IBM recently release an analysis of smart-card designs > that involved the use of residual memory imprints for recoverying private > key information. I can find the references if you want. In addition, ifg > you will search thru the patent database, you will find that the NSA holds > about 40-50 patents in "data recovery" techniques. > > WHile it's not cheap, there are quantum residuals left behind in all > environments which are measurable. Please note that I am *not* questioning whether, given analog access to the storage device, previous data state(s) can be recovered; this is a given. What I *am* questioning is why this is a requirement in a purely software environment, where it is not possible via software to determine anything other than the current value of a given storage location. The only methods for obtaining the previous contents of a storage location involve physical analog access to the hardware, and if you have this then system security has already been compromised because you could have recorded the original value when it was current. > That having been said, the pattern is more important on magnetic media, > rather than DRAM. But I say use it all the time. In fact there is a > specific set of 8 bit numbers that are tto be written in a specific order > that are designed to exercise the memory in a specific pattern. I can get > these if people are interested. Probably -chat and crypto-paranoia material. I'd like to see the pattern and any commentary from people that might be able to map it onto the behaviour of old core and/or bubble systems, for amusement value if nothing else. mike
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