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Message-ID: <2cc3d54adc359e2a7bb6051c808d32c9@smtp.hushmail.com>
Date: Tue, 18 Apr 2023 18:28:54 +0200
From: magnum <magnumripper@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: Birthday paradox
On 2023-04-18 17:57, magnum wrote:
> Can anyone point me to a (approximation) formula for the birthday
> paradox, where for example we have a bitmap with 4096 bits and populate
> it with 1024 random bits. What is the expected number of bits set in the
> bitmap?
>
> I think the answer is ~907, as that's what I'm seeing in my experiments
> - and also what this simple script shows:
Talking to the duck works every time :)
Found it at
https://jaxwebster.wordpress.com/2012/01/24/expected-number-of-different-birthdays/
It's as simple as 4096*(1-(4095/4096)^1023) where ^ means power of, as
in bc(1):
$ bc -l <<< '4096*(1-(4095/4096)^1023)'
905.35038980915274346496
magnum
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