Messages in this thread | | | From | Peter Monta <> | Subject | Re: Continuing /dev/random problems with 2.4 | Date | Fri, 1 Feb 2002 12:56:05 -0800 (PST) |
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> > > Anything that is meant to be a server really pretty much needs an > > > enthropy generator these days. > > > > Many motherboards have on-board sound. Why not turn the mic > > gain all the way up and use the noise---surely there will be > > a few bits' worth? > > Even if you think you have a good true source of random noise, you need > to run good fitness tests on the data to ensure it's truly random.
Well, yes and no. What you really need is a conservative estimate of how much entropy is contained in n bits of input; a cryptographic hash, such as MD5, will distill out the "truly random". The comments in drivers/char/random.c claim that the input hash is cryptographically noncritical, but to be pedantic, maybe MD5 the audio noise before writing to /dev/random.
Assuming the sound-card output looks like reasonable noise of a few LSBs amplitude, a conservative estimate might be 0.1 bit of entropy per sample. This is 9600 bits of entropy per second from a stereo card, more than enough.
A small daemon would wake up every so often, check if /dev/random needs topped up, read some audio samples, MD5(), write(), ioctl(# of claimed entropy bits). I haven't seen the i810 RNG tools, but I guess they do something similar. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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