Random Bit Generator

Nope! An infinite number of gates has yet to be made. One of the attributes of a large set of truly random numbers is the fact that ANY sequence can be repeated, again and again - but not for an infinite period.

Ahh..you agree with me.."scramble pseudo-random shift registers".

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Relay pullin time and bounce would make a nice randomizer, too.

Unclocked ring oscillators are not deterministic. They will drift all over the place with time, temperature, tiny Vcc variations, thermal noise, and EMI from other sources. CMOS oscillators have ghastly phase noise.

The external RC thing can be made truly random, too.

Random, in this context, means that future states can't be predicted, even given total knowledge of the hardware and the current state. Which means that bad guys can never decode the pattern.

John

"Never attribute to malice what is done in the name of Marketing"

I am not sure how many random bits could be extracted from one click of a relay. Once I tested reed relay for life expectancy; the bounce pattern looked very repeatable. BTW, the life term appeared to be not so great: somewhat 500K cycles or so.

Agreed. Typical RMS jitter ~ 1% of the period, and a big part of it is due to the unpredictable noise of the components.

One should be very careful with the assesment of the amount of the true random information. It is easy to make a RNG which could seem very solid from first glance, but it would fail to the basic analysis.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

ly

So their web-site is broken. How come you didn't manage to work this out?

The sloppy work was yours - you picked up a link to an obviously corrupted data sheet, and present it to the user-group with a snide comment, rather than finding a non-corrupted data sheet.

Probably for the same reason that Philips stopped making the SD214 - too much like hard work for a relatively small market.

Fairchild would appear to have put an idiot in charge of the relevant bit of their web-site. These things happen. At least it isn't a nuclear reactor.

-- Bill Sloman, Nijmegen

If you timed the bounces to ns resolution, they would be pretty noisy. Temperature, vibration, coil voltage variations, all sorts of things would vary the timing and bounce details. Of course, using a relay for making random numbers is a whimsy, not a very practical idea.

I agree about reeds. Even at low switching levels, they aren't very reliable.

John

Does not matter..it cannot generate any (and all) given pattern more than once in a row..so it does not pass specs.

Not quite..the _probability_ of any repetition is related to the bitlength under observtion, factored into all of the other possible groups. Repeat N times, and the probability, starting near zero, gets so small that the engineering zero is most likely larger..

Mercury-wetted reed relays do last longer - about 100 million operations - and the contact resistance is pretty stable. They do need to mounted close to vertical - people did keep offering oerientation insensitive mercury reeds, but they never seemed to stay on the market for any length of time.

-- Bill Sloman, Nijmegen

Does anybody know that that means?

John

No such luck. Personally, I'd suspect that you'd have relatives working for Fairchild, but there must be other genetically impoverished groups in the US (like the Jukes and the Kallikaks).

-- Bill Sloman, Nijmegen

Yes, and they had progeny.

Fortunately, that won't be so in your case.

So Slowman is a Kallikaks-disposition family? ...Jim Thompson

In article , John Larkin writes: ...

But if I know the current state and a rough estimate of the frequency, and when the good-guys grab some random bits, I can reduce the search space to something reasonable to attack with brute-force.

Yep. Back in the early 1970's there was a military HF radio modem that used them in pairs to demodulate rolling QPSK (45 degrees roll each frame). The Q would have to be pretty high to use them that way. They were demodulating some 15 tones simultaneously, and they were driven for one frame and used as reference for the next. The symbol rate was not very high, like 50 symbols per second, so they had to stay on phase for some time. I think the Qs were in the 10,000s range.