Re: Can birthday problem be applied in bruteforce
- From: Fabrice <fabrice.gautier@xxxxxxxxx>
- Date: Tue, 29 Sep 2009 15:14:11 -0700 (PDT)
On Sep 29, 12:47 pm, Bipin <bipin.gau...@xxxxxxxxx> wrote:
Hi,please consider my novice question:
i was reading the Birthday problem in wikipedia
http://en.wikipedia.org/wiki/Birthday_problem
"In a group of at least 23 randomly chosen people, there is more than
50% probability that some pair of them will have the same birthday.
Such a result (for just 23 people, considering that there are 365
possible birthdays) is counter-intuitive to many. For 57 or more
people, the probability is more than 99%"
Question: So, to bruteforce a randomly choose 128 bit key, only 3.1 ×
10^19 random tries are necessary to find the key? (considering
birthday problem/attack)? [1] So, can birthday problem be used
effectively to find for a randomly choosen key, with random bruteforce
attack? Could this way be quicker than a full keyspace search with
bruteforce?
What the chart means, i think, is that if you randomly generate
3.1x10^19 keys of 128bits, you have 75% probability to have at least 2
identical keys in your set.
It does NOT say that you have 75% probablity to find a second key
identical to the first key you generated (or any particular key).
To explain in term of birthday paradox, if you are in a room with 57
random people, you have 99% chance to find 2 people with the same
birthday, but NOT 99% chance of finding one with the same birthday as
you.
.
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- Can birthday problem be applied in bruteforce
- From: Bipin
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