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Len:
10mhz? My gawd man, I can walk that fast! I stand behind what I said, no perfect random number generators exist, if you need a really good one--it can't be done with computer algorithms (but, the one doing our lottery is a really **** poor one--probably worse than your "no repeats for 913 year one @ 10mhz" even... grin It most EXACTLY becomes a question of, "How good of a random number generator do you need?" I grant you, most apps do not need that good of one, games of chance in reno/las vegas are ran off damn poor ones... Also, if you read about egg at princeton.edu, you will see that computer random number generators are really a bad idea, the human mind can influence results... on some quantum-metaphysical level it seems the mind has powers which we have only guessed about in fairy tales... I leave that to your further research however... Remember Len, we really do agree on most though... or, close enough... John wrote in message ups.com... From: John Smith on Jul 29, 1:12 pm an_old_friend: Perhaps spread spectrum is used by spies, who knows, or sat links--we will always catch only the poorest of spies--undoubtedly they DO NOT represent the "good ones." But, most radio is a poor vector for spies, the internet is a much more viable medium... Ahem...those "number stations" on HF aren't for sports scores or lottery numbers... :-) A true "random number generator" has escaped being ever realized in a practical form. Untrue, John. PRSG (Pseudo-Random Sequence Generators) have been in common use in both communications and instrumentation for about three decades now. Using just 9 standard digital logic packages with a 10 MHz clock, the PRSG I built for instrumentation would not repeat until 913 years had passed. Reference: Electronics Designer's Casebook Number 3, a collection of Electronics magazine articles published between February '78 and January '79. I was the author of that. "Electronics" magazine was a bi-weekly industry/subscription periodical published by McGraw-Hill; McGraw Hill morphed it into four separate monthlies. The "random noise" from the background radiation of the universe comes very, very close. No, does NOT "come close," that IS the definition of random. In computing, if a very high quality "random number generator" is needed, it will always be outboard (white noise generator.) No computer algorithm ever developed is able to generate REAL random numbers. Success is only measured in how close they can come to the ideal... Sigh. PERIODICITY is at question? I would say that a repeat period of a century or more is pretty dang good. Periodicity greater than that is found in the DES and some of the algorithms at the NSA. SOME finite periodicity is NECESSARY to set code keys and thus enabling a decode to start to prepare to get ready to begin. That just cannot be done with true random noise thingies. In some of the Swiss (formerly Swedish) Crypto AG products, a true natural random noise source generates the random key patterns for both encryption and decryption sequences. A problem there is that the decrypt sequence MUST be identical to the encrypt sequence and that decrypt sequence transported to a recipient. With the DES and similar PRSG-driven sequences, the decrypt key is NOT required to be sent separately...all that is required is to set the sequence at some pre-determined state (the "code key" enters that) and this aligns the sequence with the received sequence...a sync is possible and decrypt can proceed. As to "simple algorithm" periodicity, a 913 year pattern repeat at a 10 MHz clock is quite long. That was achieved with a 2^33-1 sequence bit pattern Exclusive-ORed with a 2^25-1 bit pattern. Each of the individual PRSGs had NO common factors in periodicity so they Ex-ORed to a pattern of 2.88 x 10^17 clock periods. That could be implemented on any PC (I did that just for funzies) with a 2 GHz clock and sequence faster than the hardware version clock at 10 MHz. So that one repeated about every 100 years... ... the "noise" from a large number of typists keyboards might be close enough, although not perfectly random, for some applications... The humans-replacing-monkeys (at the KGB) was taken from David Kahn's "The Codebreakers" and was a quote from someone else. Today, at this "late" hour of 5:15 PM PDT, thousands of WLANs are very busy within RF range of one another, NOT interfering with each other thanks to some clever and longer PRSGs. All those WLANs can also synchronize with one another should they have to start from power-down condition. Add to that the garage door openers which have a very short data burst on an RF carrier...add millions more in remote keyless entry automobile "watch fob" transmitters. Their pattern security is so good that they CAN and HAVE replaced mechanical counterparts in any environment. [yes, the auto fob transmitters have keys attached as a security in case the car battery goes kafooey...and for the mental/emotional security of the numbnuts conservatives who don't trust those new-fangled digital gizmos] For pseudo-random number generation in theory, along with tests on things therein being random, there are 155 pages worth of good stuff in Donald E. Knuth's "The Art of Computer Programming," Chapter 3, Volume 2. I have the three-volume set and will entertain any offers of purchase (plus shipping costs)...provided I can trust the buyer (this group doesn't ensure my trust much...). bit bit |
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