[147813] in cryptography@c2.net mail archive
Re: [Cryptography] [RNG] on RNGs, VM state, rollback, etc.
daemon@ATHENA.MIT.EDU (John Gilmore)
Tue Oct 22 20:07:26 2013
X-Original-To: cryptography@metzdowd.com
To: cryptography@metzdowd.com, gnu@toad.com
In-reply-to: <526662F7.9090807@borg.org>
Date: Tue, 22 Oct 2013 14:51:02 -0700
From: John Gilmore <gnu@toad.com>
Errors-To: cryptography-bounces+crypto.discuss=bloom-picayune.mit.edu@metzdowd.com
>> physical RAM (/dev/mem) into the RNG pool at boot time...
> Unfortunately, since I had my brainstorm, RAM technology seems to have changed and in my observation recent RAM comes up nearly all zeros.
Any computer that checks parity on its main memory, or uses ECC error
correcting codes on its main memory, will have to initialize its main
memory after power-on. In x86's this is often done by the BIOS.
Failing to do this initialization would cause later main memory reads
of uninitialized variables to produce spurious parity or ECC errors
(spurious in the sense that the memory chip has not failed to retain a
value previously written to it).
Many modern memory controller chips automatically support parity or ECC,
depending on which memory DIMMs are plugged in. One extra bit per byte
allows parity protection or (with 64-bit buses) ECC.
John
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