Date: Tue, 08 Oct 2002 10:22:36 -0700 From: "Kevin Oberman" <oberman@es.net> To: Peter Leftwich <Hostmaster@Video2Video.Com> Cc: FreeBSD LIST <freebsd-questions@FreeBSD.ORG> Subject: Re: /dev/urandom is randomly cool Message-ID: <20021008172237.0034D5D04@ptavv.es.net> In-Reply-To: Your message of "Tue, 08 Oct 2002 00:30:27 EDT." <20021008002612.C35848-100000@earl-grey.cloud9.net>
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> Date: Tue, 8 Oct 2002 00:30:27 -0400 (EDT) > From: Peter Leftwich <Hostmaster@Video2Video.Com> > Sender: owner-freebsd-questions@FreeBSD.ORG > > On Mon, 7 Oct 2002, Oliver Fromme wrote: > > Peter Leftwich <Hostmaster@video2video.com> wrote: > > > On Sun, 6 Oct 2002, Fernando Gleiser wrote: > > > > On Sun, 6 Oct 2002, Mikko Ty=F6l=E4j=E4rvi wrote: > > > In this particular case, you can use head instead of dd: > > tr -cd a-zA-Z0-9 < /dev/urandom | head -c 8 > > Thanks for that! I was trying `cut -c` and didn't realize head had that > flag. Now I can generate 8 characters: > > # tr -cd a-zA-Z0-9 < /dev/urandom | head -c 8 ; echo "" > 0tXx3p3m > > ..and random phone numbers :) > > # tr -cd 0-9 < /dev/urandom | head -c 10 ; echo "" > 5031594488 > > Why is this an entropy pool and not an entropy ocean? Is there a way to > cat /dev/dsp or analyze my soundcard's mic-in and sample randomness? Just how random is your sound card input? That is very dependent on details of the A-D conversion and it may be FAR from really random. The system is, justifiably paranoid! If you add some devices to the entropy generator, you will get an entropy ocean! I recommend the keyboard and mouse for a workstation. The network interface is USUALLY a good one. The disk interface is possible, but can to be less random than is ideal. Clocks are a bad idea. :-) Use vmstat -i to get a list of interrupt sources on your system and use rndcontrol to add them to the entropy engine. # vmstat -i interrupt total rate ata0 irq14 3240348 10 ata1 irq15 4 0 mux irq11 1342389 4 pcm0 irq10 3401 0 fdc0 irq6 2 0 atkbd0 irq1 58469 0 psm0 irq12 872780 2 sio0 irq4 441098 1 clk irq0 31225225 99 rtc irq8 39970907 128 Total 77154623 247 # rndcontrol -s 11 -s 1 -s 12 rndcontrol: setting irq 1 rndcontrol: setting irq 11 rndcontrol: setting irq 12 rndcontrol: interrupts in use: 1 11 12 This is a pretty good way to get some significant data into the system. the mouse/keyboard are always the best choices. The network is normally pretty good, although some activity is pretty regular, but not to the degree that should impact entropy. R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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