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A comment on Times Pulls Article Blaming Encryption in Paris Terror Attack. Parent comment

Re:Times Pulls Article Blaming Encryption in Paris Terror At... by 542458 on Tuesday November 17, 2015 @04:48PM (#10584207)
No. What you described will work for a simple substitution cypher, but not for a one time pad. A one time pad is the same length as the message, and permutates every letter independently. Trying all keys will yield every possible plaintext. For example the phrase:

"The swallow flies at midnight"

May (with a one time pad) be encrypted into

"WD4oXOl8yO0QtD4sOf7ip0P7ScIia"

(which, incidentally, is indistinguishable from random noise)

If you just bruteforced that by xor'ing every character with every other possible character you could derive every possible message of that length, such as:

"garfield hate lasagna someday"

"men are cats why even bother?"

"pocket knives go to space yay"

etc ad infinitum

No measure of semantic analysis will help you here!

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Re:Times Pulls Article Blaming Encryption in Paris Terror At... by mewse on Tuesday November 17, 2015 @05:21PM (#10584428)
Well-known caveat for people who are familiar with encryption, but it's worth calling out explicitly here:

If you use the same one time pad to encode two or more different messages, then all the sorts of attack proposed here become plausible again.

The security provided by a one time pad relies entirely on the fact that it is only ever used once.

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Re:Times Pulls Article Blaming Encryption in Paris Terror At... by sold on Tuesday November 17, 2015 @06:06PM (#10584670)
I'd like to add this scenario actually happened during the Cold War. Soviets were reusing one time pads and the US army decrypted some of the messages, among other things this lead to discovery of Soviet spies targeting the US nuclear weapon program https://en.wikipedia.org/wiki/Venona_project
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Re:Times Pulls Article Blaming Encryption in Paris Terror At... by pdkl95 on Tuesday November 17, 2015 @06:55PM (#10584905)
https://www.youtube.com/watch?v=yxx3Bkmv3ck

Computerphile recently showed how this was done.

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Re:Times Pulls Article Blaming Encryption in Paris Terror At... by zrth on Wednesday November 18, 2015 @08:50AM (#10587629)
Is it really still a "one time pad" if you used it multiple times?
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Re:Times Pulls Article Blaming Encryption in Paris Terror At... by tripzilch on Tuesday November 17, 2015 @05:14PM (#10584388)
Easy to tell the right sentence because it's the only one capitalized correctly! /s
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Re:Times Pulls Article Blaming Encryption in Paris Terror At... by noselfrighteous on Tuesday November 17, 2015 @04:50PM (#10584223)
Ahh yep, got it.
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