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Carrock

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Everything posted by Carrock

  1. As Strange mentioned a long time ago, confirmed by some of my friends, the Mensa lower membership limit is 148 and Mensa pass scores range from 149 to 152 - at least from 5 samples (6 including Peterkin's example). Explains the fact that an an improbably large number of apparently intelligent people think a good use of their time is to hang out with people who, like them, are good at 'passing' IQ tests. The test has to be optimised for an IQ range. The highest IQ for an individual test corresponds to getting all the answers correct.
  2. As you've mentioned reciprocity a few times in this thread, just a clarification that reciprocity is not always valid. From Electromagnetic Reciprocity This is commonly used in radar, when the transmitter and receiver are both permanently connected and are effectively part of the aerial; output power to the rest of the aerial is from the tx, while input power is to the rx, isolating tx and rx. Using the ionosphere for radio communications similarly sometimes produces non reciprocal paths.
  3. A win-win question from you. It's in the public domain that Britain's Official Secrets Act is pretty draconian and signing it is for life, not just Christmas. So if I answer 'no' I'm lying or telling the truth. If I answer 'yes' I'm lying or breaking the Official Secrets Act. A few people who had very high level clearance: Burgess, Philby, MacLean, Blunt, Cairncross, Fuchs, Gold, Greenglass, Hall etc. In case there is any truth in what you've said, this is my last post on this thread.
  4. Except when your son is carrying clear messages to the captain or other crew. As someone who chose not to start WW3 by faking messages, I'm surprised he didn't end up as chief of naval operations. Silly me, I didn't for a moment believe that was true. Like you, I'll go with vicarious achievement. Best I can come up with is my dad was on various merchant ships escorting U.S. - Britain convoys in WW2. Only got his feet wet once when the wheelhouse windows were smashed by a nearby shell. BTW none of my close family, including my father, were in the military, so you 'win' on that. So the unimportant things like ship's orders are fine for the radio operator to know. Next post Is the radio operator trusted not to make his own private copy? If not, whoever searches him when he leaves would need the same clearance as he might see a decrypted message. Much better of course for the radio operator to memorize the messages.
  5. That's interesting. I know a few people who were radio operators on commercial ships decades ago and none of them were able to decrypt secure messages not addressed to them. If, very improbably, the captain gave decryption information to your son, he deserved to be court-martialed and his security clearance revoked. Even worse is the idea that there are people in the U.S. military whose job includes having unnecessary access to highly secret information. 😧
  6. I don't know but probably just some saddo annoying me. It's the first time anyone's ever made even a token effort to hack me AFAIK. Updating my password on my various devices was tedious but probably very low security risk.
  7. Nor me. However, hacking my email enough (more if competent) for my ISP to change my password and inconvenience me was a lot simpler/cheaper. It's rather sad that mentioning public domain work by Frank Miller (1882) and Hedy Lamarr (1942 patent) is considered worth this response.
  8. There's an arms race between security and hacking in encryption and I hadn't really thought about the internet, computers and O.T.C. The securely encoded data in O.T.C. is actually encode once, send, copy or read many. Only the copies of the O.T.C. key must be held securely. So send an encrypted file via internet to another computer as described by Sensei. DOS attacks etc don't deplete O.T.C. as the same encrypted data can be resent. For best security copy the file to a computer which never has internet access. Plug in a memory stick with a copy of the one time key used by the originator. Run a simple program which uses the one time key to decrypt the file. Don't save the decrypted data , unplug the stick and switch off the computer when finished. The O.T.C. doesn't need to be significantly larger than the total of all files sent.
  9. O.T.C. isn't particularly suited for sending vast amounts of data or for the internet as I hinted at in my preference for cheap and crude over sophisticated and expensive. Fairly secure encryption is pretty much necessary for the internet. To avoid rather than solve these problems, if phones with their metadata are also unsuitable, one of many alternatives: frequency hopping radio with one time code to set the frequencies. This is very hard to jam and a fairly secure version is widely used by the military and other clandestine communicators. One time code isn't normally practical for large numbers of users. Probably civilians couldn't get a license as governments like to eavsdrop.
  10. For some forgotten reason I originally assumed you meant random data from the sender rather than malicious interference. Malicious interference can disrupt any communication; the important point with O.T.C. is never ever reuse it for any reason.
  11. I don't see why anything but noise would cause desynchronization. To (re)synchronise if frequently needed, use a predefined part of the key (different each time) to send e.g. ZZZZZZZZZZafdc74cf to indicate the next byte used for message encryption. Fairly straightforward software could be used to find which part of the key decodes as ZZZZZZZZZZ. Goods e.g. a key can be sent by trusted courier which has been possible for a few thousand years. This code, like any other, relies on physical security. Any finite length one time code code will, if generated often enough, eventually repeat by random chance, in this case (64GB) after at least many billion uses, but that doesn't assist decoding. A recommended way here is to use a noisy reverse biased diode in avalanche mode and an analogue to digital converter to generate the code. With some care, the slight preferential bias for some digits can be made far too small to be useful for decoding. I don't think knowing the algorithm would help. The important issue here is to realize that crude and cheap is much better than sophisticated and expensive. An ancient phone with no internet access and only text and voice can't be hacked without physical access, assuming the phone designer was honest and competent. Some software would be needed for de- and encryption. If the phone was stolen, all its one time code would be compromised but not other phones with different one time code. If you want to annoy a spook monitoring your comms, send this plain text message first. 'To make sure you get the full list of our secret agents in Britain, I'll send it 10 times. Naturally you use different parts of the one time code for each message and actually send it 1000 times. One time code is inconvenient but has its advantages. I recall many years ago hearing people droning out interminable lists of numbers on short wave radio; my first experience of one time code.
  12. Slightly off topic, but defeating quantum decryption is quite simple (human stupidity excepted) and the technique has been known since at least 1882. From Wikipedia In cryptography, the one-time pad (OTP) is an encryption technique that cannot be cracked, but requires the use of a single-use pre-shared key that is larger than or equal to the size of the message being sent. A couple of phones, each with say 64GB identical one time code storage and no ability to change the software without physical access should be fine for a few years of communication. For obvious reasons, adverts for increasingly powerful phones and encryption rarely mention this.
  13. From later in the Truth Table wiki So, I think, this wiki is stating that you can have a truth table with or without the additional steps required to implement it, which seems rather obvious. Complementary to Studiot, I can't see any way to implement a nontrivial truth table without at least logic gates. The Wiki refers to Logic Gate for practical implementation...
  14. Wikipedia is certainly oversimplifying. Like, say, a photon, a virtual photon is calculated or observed to exist from when it is created to when it is destroyed, which for massless virtual particles has no upper time limit. The second sentence is is even more misleading. Oppositely electrically charged particles experience a net attraction by exchanging virtual photons; this attraction does not happen with real photons but the arguably very different characteristics of virtual and real photons in this instance does not shorten the virtual photons' lifetime.
  15. What description? Photons, for example, are stable and therefor virtual photons have infinite range.
  16. [morbid] Can anyone confirm that the domain owner is immortal, or at least that their will won't take a couple of years to clear probate? [/morbid]
  17. After I recently discovered this serial has been made publicly available I immediately watched it again.... "Young Dracula," is a tragicomic fantasy melodrama for children and adults, spanning six years, dealing with the battle between evil and good from the viewpoint of Count Dracula's children: Ingrid, 14, and Vlad, 12, who know they will soon transform into evil, bloodsucking vampires, or cease to exist. The dialogue, plot and character development are IMO better than most adult tv drama. It's now available on the BBC IPlayer and also free on UTube
  18. From the report, a single software failure in calculating a flight path was designed to cause a fatal exception i.e. crash the whole system rather than e.g. generate a 'NOT VALID FLIGHTPATH -MANUAL INTERVENTION REQUIRED' warning for controllers. The backup system must have been designed solely for hardware failure since as soon as it was enabled it experienced the same software failure and crashed. This particular problem has been fixed so crashing the system was always an unnecessary requirement in handling this safety critical information. The claim that this failure, after 15 million successful flight plans, is a ''“one in 15 million" software failure event' implies that there are no more unintended fatal exceptions in the software. Really? Fortunately the whole system is now getting a very necessary upgrade.
  19. I can't see how to do this without at least implicit equations...
  20. Gets worse than that. Sometimes in the same system work done in e.g. charging a capacitor is regarded as positive, while work done discharging a capacitor is, er, positive. You can then say (e.g. from https://www.allaboutcircuits.com/textbook/alternating-current/chpt-6/q-and-bandwidth-resonant-circuit/ ) You can actually buy a power buildup cavity using the same general idea. From Wiki It seems like you could put in 10mW and get 1 MW out. Apparently the concept of imaginary power or reactive power (which is not available for continuous work) is not used here; 'stored power' is just power. It's rather like saying torque is energy because the units are dimensionally the same. There's a simple definition of Q to avoid this confusion* Q(omega)= omega*(maximum energy stored/power loss) *My confusion anyway - there must be some rationale to the "stored power is not energy" concept.
  21. Could the same amount of power as is in the (I presume resonant) cavity be continuously removed from it and it still be a buildup cavity? If not, some of the power is no more available than the power of a swinging pendulum as it converts kinetic energy to potential energy and back to kinetic energy again. I might try to convince a keen equestrian non-scientist that going for a walk to warm up is more eco friendly than sitting in front of a four horsepower heater. He might disregard my suggestion as horsepower is not electrical.
  22. Maybe misleading? I think you're referring to what engineers call reactive or imaginary power, which is related to stored energy and is measured in volt-amperes, not watts.
  23. Croatia went in for extreme lockdown but it also seems to be doing a lot of testing and presumably contact tracing etc. IMO the most important thing NZ and Croatia have in common is they first treated Covid as a serious problem less than a month after their index case. So many other countries seem to have decided to wait and see if the predictions by WHO etc of a major epidemic were correct before doing anything. (CharonY's comment also relevant and helpful.)
  24. I chose NZ because it was well documented (see the length of the wiki article). I don't believe any country could pretty much eliminate cv without "establish effective work procedures, organize tracking teams, educate population." No need for a major expansion of hospital capacity in NZ though. Cynically, there's one very good reason it's unlikely NZ leaders will allow a resurgence. From 13th April:
  25. Time for a mention of New Zealand and its coronavirus on this forum... After 21 deaths and with 65 still active cases it is down to level2 lockdown i.e. just maintain social distancing. The country was put into full lockdown less than a month after the index case. https://en.wikipedia.org/wiki/2020_coronavirus_pandemic_in_New_Zealand https://www.cnbc.com/2020/05/05/how-new-zealand-brought-new-coronavirus-cases-down-to-zero.html
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