Re: Shuffled Poker Deck

From:

"Daniel Pitts" <googlegroupie@coloraura.com>

Newsgroups:

comp.lang.java.programmer

Date:

23 Jan 2007 13:46:34 -0800

Message-ID:

<1169588794.107613.250180@13g2000cwe.googlegroups.com>

Daniel Dyer wrote:

On Tue, 23 Jan 2007 21:27:28 -0000, Daniel Pitts
<googlegroupie@coloraura.com> wrote:

Daniel Dyer wrote:

(http://www.pokerstars.com/poker/room/features/security/).

Hmm, There is a problem in their explanation:
"A deck of 52 cards can be shuffled in 52! ways. 52! is about 2225. We
use 249 random bits from both entropy sources (user input and thermal
noise) to achieve an even and unpredictable statistical distribution."
They are right about the 52! ways, but 52! is around 1.55e66, not 2225
The number of bits required to store that is 220, Ohwell.

I think that must be a typo. I'm certain I read that page before and it
said 225. I've done the same calculations previously and got 226.

Okay, I see three problems.
First, my mistake: I calculated 51!, not 52!
Second, their typo. They should ceil that value anyway, so it would be
226
Third: The're lack of units.
The statement probably should be:
"All values for 52! can be represented in 226 bits"

Oh, and 52! is around 8.066e67, python lets you calculate it exactly:
echo "print reduce(lambda x,y: x*y, xrange(1, 53))" | python