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Originally Posted by acropolis
that's surprising to me.
i have to assume that maybe for a 1kb pad encrypting a 2k message, it would be pretty easy (yes?).
but for, say, a 1Mb message, encrypted with a pad (of unknown length) probably somewhere between 1.1 and 3 times (so i guess the pad being between 300kb and 900kb) would it still be 'easy'?
how would you go about it?
(or are we restricting ourselves to short messages?)
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Me and megla only played with short messages. I believe random pad lengths would still be very easy for an amateur to break. It's just looking for patterns. In fact XOR on plain text has a weakness for random key lengths. Consider what happens if you have two plain text strings each XOR'd with the same code. XOR them with each other; one simple test is you'll find this clears bit seven. Then you just need to do this for each possible key length. This could be easily fixed by randomising bit 7, but you'll still have bit six cleared on something like 70% of the letters. This is real amateur stuff. I have no idea how to crack compressed files, say.