Re: What's the probability that 2 files of n bytes have the same hash using SHA1?
 From: unruh <unruh@xxxxxxxxxxxxxxxxxxxxxxx>
 Date: Tue, 15 Dec 2009 16:28:12 GMT
On 20091215, PeterMacGonagan <rodrigue.roland@xxxxxxxxx> wrote:
Ok, thank you for all your answers.
I read about the birthday paradox and I think I undestand it. As we
can read, we can approximate the number of attempts to generate a
collision using brute force by:
Q(H)\approx \sqrt{\frac{\pi}{2}H}.
For a 160bit hash, there are 2^160 possibilities (approximately
1,4615e+48 different outputs). So, it'll take approximately 1.515e+24
attempts to generate a collision (2^80 = 1.2e+24).
Well, depends on what you mean by "collision". It it means "find two
files with the same hash" you are right. If it means ( find a second
file with the same hash as this given file) then this is wrong. It would
take 2^159 on average.
.
 References:
 What's the probability that 2 files of n bytes have the same hash using SHA1?
 From: PeterMacGonagan
 Re: What's the probability that 2 files of n bytes have the same hash using SHA1?
 From: Kristian Gjøsteen
 Re: What's the probability that 2 files of n bytes have the same hash using SHA1?
 From: PeterMacGonagan
 What's the probability that 2 files of n bytes have the same hash using SHA1?
 Prev by Date: Workshop “Medical Imaging Systems” within EUROMEDIA 2010 – Announce & Call for Papers
 Next by Date: Re: finding multiplicative inverse of n
 Previous by thread: Re: What's the probability that 2 files of n bytes have the same hash using SHA1?
 Next by thread: Re: What's the probability that 2 files of n bytes have the same hash using SHA1?
 Index(es):
Relevant Pages
