I have the feeling this could be trivially solved by adding reset lines to the RAM design, and triggering them on shutdown (perhaps powered by some capacitor).
I don't think that would be trivial at all. How would it work?
Cryogenically frozen RAM bypasses disk encryption methods (2008)
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Re: Cryogenically frozen RAM bypasses disk encryption methods (2008)
#32I have the feeling this could be trivially solved by adding reset lines to the RAM design, and triggering them on shutdown (perhaps powered by some capacitor).
I don't think that would be trivial at all. How would it work?
Have a look at the design of a DRAM cell (search for it in google images). Basically you can just pull all the address lines high, and set the bit lines to ground. SDRAM works similarly.
Re: Cryogenically frozen RAM bypasses disk encryption methods (2008)
#33Re: Cryogenically frozen RAM bypasses disk encryption methods (2008)
#34Earlier quoted context omitted.
Wouldn't the embedded aluminum particles cause a risk of shorting out the electrical connections?
> Pure Electrical Insulator: > Arctic Alumina Adhesive is a pure electrical insulator, neither electrically conductive nor capacitive. I'm not entirely sure I understand what it means by capacitive in this context, but, not conductive and the overall sentence there seems to strongly indicate that it specifically will not short out.
Not capacitive means that there are no isolated electrically conductive layers that act as capacitors. That is, the stuff isn't only non-conductive for DC. The alumina also increases thermal conductivity, and strengthens the epoxy, making removal much more difficult.
Re: Cryogenically frozen RAM bypasses disk encryption methods (2008)
#35There has been some more recent work on this lately: https://www.dfrws.org/2016eu/proceedings/DFRWS-EU-2016-7.pdf Essentially, with newer RAM (DDR3), the location things end up on the physical chip is scrambled to improve reliability: > Storage of bit streams which are strongly biased towards zero or one can lead to a multitude of practical problems: Modification of data within such a biased bit stream can lead to co…
I didn't know DDR3 RAM was scrambled. Thanks for the link & tip. Analog scramblers of the past were defeated in a number of simple and clever ways. Most security engineers stopped trusting scrambling as it almost always fails. A useful obfuscation at best on top of genuine encryption and authentication in RAM as in my other comment. No surprise we have another one on breakers' resumes in the RAM area. Note: Nice shor…
scrambling != encryption
scrambling is done in a lot of systems, especially in telecom to condition the signal to have some special signals processing property (reducing DC level, changing spectrum shape, etc)
Re: Cryogenically frozen RAM bypasses disk encryption methods (2008)
#36Earlier quoted context omitted.
I don't think that would be trivial at all. How would it work?
Have a look at the design of a DRAM cell (search for it in google images). Basically you can just pull all the address lines high, and set the bit lines to ground. SDRAM works similarly.
But that would require an immense amount of current, compared to what those lines can ordinarily source. That's what I'm talking about. High current density can cause problems with electromigration.