[Cryptography] RAM memories as one source of entropy

Kent Borg kentborg at borg.org
Sat Feb 8 12:52:50 EST 2014

Reading plain-old DRAM at power up seemed like a good idea to me, and I 
have done it years ago on the "can't hurt" theory, but on recent 
hardware it looks like CPU reads from DRAM right after boot are almost 
entirely zeros.  Something has changed in the technology, there used to 
be lots of patterning when I did that.

That doesn't mean that there might not be other ways to get interesting 
entropy from DRAM, just that is doesn't seem to be free for the reading 
in recent hardware; you might have to do some hardware engineering to do 
it, at which point there have got to be better ways to add some 
entropy-yielding hardware to your design.


-kb, the Kent who doesn't know about SRAM.

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