How do you determine how many guesses an attacker would need toguess a key or keystream? (stream ciphers)
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From: unruh on 23 Jan 2010 12:41 On 2010-01-23, mark <cheesemonkey22(a)gmail.com> wrote: > Sorry for the newbie question. What difference would it make for an > attacker with respect to trying to guess an input key into a stream > cipher, versus trying to guess the outputted keystream? > > If you put a key into some stream cipher, it may use several LFSR's to > help encrypt your message. Assuming something like the E0 cipher (but > not limited to that cipher) (http://en.wikipedia.org/wiki/E0_%28cipher > %29), how do they impact whether it is smarter to guess a key versus a > keystream? Since the keystream is typically longer than the key, it is harder to guess. also, you have no criteria for deciding whether you have guessed the right stream or not (See One Time Pad and its proof of security). > > Thanks :) |