4 ms·

It is important to note they could access an image in the memory up to 0.75 seconds after cutting power, but after 1.0 seconds everything had completely decayed

It is important to note they could access an image in the memory up to 0.75 seconds after cutting power, but after 1.0 seconds everything had completely decayed. This sounds less like a "cold boot" attack and more like the residual power is still flowing on the substrate for 0.75 seconds.

anfractuosity 3y ago
I wasn't able to automate the use of the freeze spray alas, but I believe that did let me access data after more significant durations. With the freeze spray I did also manage to unplug the power cable completely and switch SD cards manually. Edit: In "Cold Boot Attacks are Still Hot: Security Analysis of Memory Scramblers in Modern Processors" they say "To assess the feasibility of cold boot attacks on today’s denser and smaller components, we measured the retention time of ﬁve DDR3 and two DDR4 modules from various manufacturers. At normal operating temperatures, a signiﬁcant fraction of the data is lost within 3 seconds of losing power." The Pi 4 I used makes use of DDR4 from what I recall.
- yonatan8070 3y ago
  What results would you expect to get if you simply put the whole setup in a regular freezer? Or if you just tried it during winter
  - anfractuosity 3y ago
    It sounds like a typical freezer cools to around -20C, I think the freezer spray I used directly on DDR chip, claims to chill to around -50C, but not sure how much the surface temperature decreases after spraying and how fast it warms up again.
    - jacquesm 3y ago
      Industrial freezers will go to -45, lab freezers to -85 before getting into really exotic stuff.
      - azalemeth 3y ago
        LN2 is 77 K (-196 ºc) and dirt cheap -- cents/pence per litre. Most electronics works surprisingly well in it, at least until it warms up and the condensation starts to be a problem ;-).
        TeMPOraL 3y ago
        What about the material physics of losing some 220°C in a second? Won't things crack from this alone?
        azalemeth 3y ago
        That's an excellent question and as you rightly highlight depends on things like ∂T/∂t that are perhaps a bit harder to control In practice, however, most electronics is fine (!) with the right materials – even a relatively bog-standard gaming CPU [1]... [1] https://www.youtube.com/results?search_query=ln2+overclocking https://www.youtube.com/results?search_query=ln2+overclockin...
NavinF 3y ago
0.75 seconds without cooling. I would not expect "residual power" to last for 0.75 seconds. Even if it did, RAM has to actively be refreshed by the memory controller. (DDR self-refresh is only enabled during sleep and I dunno if the Pi even supports that)

anfractuosity 3y ago

I wasn't able to automate the use of the freeze spray alas, but I believe that did let me access data after more significant durations. With the freeze spray I did also manage to unplug the power cable completely and switch SD cards manually. Edit: In "Cold Boot Attacks are Still Hot: Security Analysis of Memory Scramblers in Modern Processors" they say "To assess the feasibility of cold boot attacks on today’s denser and smaller components, we measured the retention time of ﬁve DDR3 and two DDR4 modules from various manufacturers. At normal operating temperatures, a signiﬁcant fraction of the data is lost within 3 seconds of losing power." The Pi 4 I used makes use of DDR4 from what I recall.

yonatan8070 3y ago
What results would you expect to get if you simply put the whole setup in a regular freezer? Or if you just tried it during winter
- anfractuosity 3y ago
  It sounds like a typical freezer cools to around -20C, I think the freezer spray I used directly on DDR chip, claims to chill to around -50C, but not sure how much the surface temperature decreases after spraying and how fast it warms up again.
  - jacquesm 3y ago
    Industrial freezers will go to -45, lab freezers to -85 before getting into really exotic stuff.
    - azalemeth 3y ago
      LN2 is 77 K (-196 ºc) and dirt cheap -- cents/pence per litre. Most electronics works surprisingly well in it, at least until it warms up and the condensation starts to be a problem ;-).
      - TeMPOraL 3y ago
        What about the material physics of losing some 220°C in a second? Won't things crack from this alone?
        azalemeth 3y ago
        That's an excellent question and as you rightly highlight depends on things like ∂T/∂t that are perhaps a bit harder to control In practice, however, most electronics is fine (!) with the right materials – even a relatively bog-standard gaming CPU [1]... [1] https://www.youtube.com/results?search_query=ln2+overclocking https://www.youtube.com/results?search_query=ln2+overclockin...

NavinF 3y ago

0.75 seconds without cooling. I would not expect "residual power" to last for 0.75 seconds. Even if it did, RAM has to actively be refreshed by the memory controller. (DDR self-refresh is only enabled during sleep and I dunno if the Pi even supports that)