[lkml]   [2003]   [Aug]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC][PATCH] Make cryptoapi non-optional?
Matt Mackall wrote:
> No, it's a premise stated at the beginning of the thread. We're
> assuming perfect distribution for x and y. The problem here is that x
> and y can be dependent or independent. If they're independent, then
> there's no issue. If they're dependent (for instance correlated or
> anticorrelated) then x^y biases toward zero or one. Which clearly has
> less entropy.

Sure, but that only holds when you assume a specific mix of
independence and dependence among the bits.

(Bits within x are independent of each other, and also within y, while
at the same time x and y are dependent.)

In general, bits from x^y do not have more bias towards zero or one
than bits from x or y alone. Consider an extreme:

x = [ random_bit_0, random_bit_0 ]
y = [ random_bit_1, ~random_bit_1 ]


entropy(x) = entropy(y) = 1
entropy(x^y) = 2

This is no more arbitrary a mix of dependence and independence than
your assumption.

-- Jamie
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:47    [W:0.161 / U:2.564 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site