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| ebastler:
--- Quote from: edy on February 13, 2020, 09:16:54 pm ---Yes I figured that much... but if there was a source of random enough information that could be gleaned by 2 observers half way around the world from each other, using a simple to remember rule, theoretically it could be the source of their random one-time pad. --- End quote --- Nope. If the seed (or rule) information required to "glean" the one-time pad is shorter than the message to be sent (and hence the length of a proper one-time pad), then the exchange will be less secure than if done with a proper, pre-generated one-time pad. An adversary could test various "seeds", each of them short, and try to decipher the message with the random number stream corresponding to that seed. That is assuming that the source of the actual random numbers is generally known and available, and only the seeds constitute the secret. The alternative would be a "security by obscurity" concept; that doesn't count anymore in cryptography these days... If, on the other hand, the seed information were as long and complex as the one-time pad itself, exchanging (sharing) only the seeds would no longer have any benefits over sharing the OTPs themselves. |
| jmelson:
--- Quote from: edy on February 13, 2020, 02:04:57 pm --- It was remarkable listening to this stuff... something I thought wouldn't be done anymore with the advent of the internet and satellite. Anyone with a $20 shortwave radio can hear the number codes and data transmission and decode it on their computer into a file of garbled data. What to do with the resultant file is another issue altogether, but certainly the USA has the means to decrypt all this stuff. Or maybe not? --- End quote --- If the encryption is done using a well-made one time pad, it is unbreakable. But, of course, distributing the one time pads to agents in the field is very difficult, and anybody caught in possession of such a pad could end up getting shot. Yes, with the internet, it sure seems like there would be better ways to send secret messages, but receiving a message requires a two-way connection, while receiving a radio broadcast does NOT reveal where you are. You ought to read the book Spycraft, it is all about how the CIA communicated with field agents and all the tricks of how they concealed their communications. Jon Jon |
| jmelson:
--- Quote from: ebastler on February 13, 2020, 09:54:36 pm --- --- Quote from: edy on February 13, 2020, 09:16:54 pm ---Yes I figured that much... but if there was a source of random enough information that could be gleaned by 2 observers half way around the world from each other, using a simple to remember rule, theoretically it could be the source of their random one-time pad. --- End quote --- Nope. If the seed (or rule) information required to "glean" the one-time pad is shorter than the message to be sent (and hence the length of a proper one-time pad), then the exchange will be less secure than if done with a proper, pre-generated one-time pad. An adversary could test various "seeds", each of them short, and try to decipher the message with the random number stream corresponding to that seed. --- End quote --- Most modern cipher gear use some form of linear feedback shift register to generate the key. Apparently, there is a mathematical process that with a short length of the key, you can figure out the specific polynomial used in the LFSR. So, some schemes have been used to make this more obscure. Just XOR'ing two or more LFSRs together doesn't destroy information, but ANDing or ORing them together does destroy information, and make this much harder. Jon |
| David Hess:
--- Quote from: imo on February 13, 2020, 11:05:20 am ---The British kept their WWII crypto stuff secret till 70ties because of German technology which became popular in Eastern Block after WWII. --- End quote --- One of the results of the British keeping their WW2 cryptography efforts secret after the war was that the US electronics and computing industries got a boost because the US did not. |
| iMo:
Some reading on the alleged cooperation of Hagelin and NSA "Secret deal between the NSA and Hagelin ยท 1939-1969" https://www.cryptomuseum.com/manuf/crypto/friedman.htm |
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