Entropy Definition (was Re: passphrases with more than 160 bits of entropy)

Greg Rose ggr at qualcomm.com
Thu Mar 23 17:50:01 EST 2006

At 22:09  -0500 2006/03/22, John Denker wrote:
>Aram Perez wrote:
>>* Can you add or increase entropy?
>Shuffling a deck of cards increases the entropy of the deck.

As a minor nit, shuffling *in an unpredictable manner* adds entropy, 
because there is extra randomness being brought into the process. If 
I was one of those people who can do a perfect riffle shuffle, 
reordering the cards in this entirely predictable manner does not 
increase or decrease the existing entropy.

So in one sense, the answer is a simple "no"... nothing you can do to 
a passphrase can increase its (that is, the passphrase's) entropy. 
You can add randomness from another source, and increase the total 
entropy, but I don't think that is relevant to the original question.


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