Messages in this thread | ![/](/images/icornerl.gif) | | From | (Måns Rullgård) | Subject | Re: [RFC][PATCH] Make cryptoapi non-optional? | Date | Fri, 15 Aug 2003 10:06:42 +0200 |
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Andries Brouwer <aebr@win.tue.nl> writes:
>> > > entropy(x) >= entropy(x xor y) >> > > entropy(y) >= entropy(x xor y) >> > >> > Is this trolling? Are you serious? >> >> These lemma are absolutely true. > > David, did you read this line: > >> > Try to put z = x xor y and apply your insight to the strings x and z. > > Let us do it. Let z be an abbreviation for x xor y. > > The lemma that you believe in, applied to x and z, says > > entropy(x) >= entropy(x xor z) > entropy(z) >= entropy(x xor z) > > But x xor z equals y, so you believe for arbitrary strings x and y that > > entropy(x) >= entropy(y) > entropy(x xor y) >= entropy(y). > > This "lemma", formulated in this generality, is just plain nonsense.
Not quite non-sense, but it would mean that for any strings x and y,
entropy(x) == entropy(y),
which seems incorrect.
-- Måns Rullgård mru@users.sf.net
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