3 ms·
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
by 542458 11y ago
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!
- noselfrighteous 11y agoAhh yep, got it.
- tripzilch 11y agoEasy to tell the right sentence because it's the only one capitalized correctly! /s
- mewse 11y agoWell-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.
- sold 11y agoI'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 https://en.wikipedia.org/wiki/Venona_project
- deleted 11y ago[deleted]