Re: [RFC][PATCH] Make cryptoapi non-optional?

[Måns Rullgård]

Andries Brouwer <aebr@xxxxxxxxxx> 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@xxxxxxxxxxxx

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