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Comment by ww520 | Hacker News Reader

One-time pad is just a generated key used once. The "time machine" will break it by trying out all keys in the key space in the time loop. If time is not an issue, brute force method pretty much breaks any crypto.

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One-time pads are still secure because the decryption process will produce every plaintext the same length as the ciphertext, and you'll have no way of knowing which one was correct.

You can't "break" a one-time pad because you can't possibly know when you've got the right "key".

Others have explained why that does not work. The way you'd use backward time travel to crack a OTP is to wait until the recipient of the message decrypts it, then your steal the decrypted message, then you go back to the time where you wanted to break the code and give yourself the message.

Another use for backward time travel is data compression. To compress a file, you simply replace its contents with a note saying when you did this. When you later want the file, just pop back to that time and get it.

This also greatly simplifies backup systems.

>Others have explained why that does not work. The way you'd use backward time travel to crack a OTB is to wait until the recipient of the message decrypts it, then your steal the decrypted message, then you go back to the time where you wanted to break the code and give yourself the message.

That's not actual decryption. You can do the same thing without time travel too, e.g by hitting the guy.

Also known as rubber-hose cryptoanalysis (https://en.wikipedia.org/wiki/Rubber-hose_cryptanalysis).

Obligatory xkcd: http://xkcd.com/538/

Here's a message encrypted by a one time pad: "AHWAM"

The key is very short, only five letters, so it should be pretty trivial to brute force. Can you tell me what the message is?

Was the one time pad HDDLC, or perhaps WJHLP or maybe BJENK or IEEOF?

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