Re: [openpgp] Fingerprints and their collisions resistance

[jbar <[e-mail]>]

On Fri, 04 Jan 2013 11:56:36 -0800
Andrey Jivsov <[e-mail]> wrote:

> On 01/04/2013 02:53 AM, Christian Aistleitner wrote:
> > Hi Andrey,
> >
> > On Thu, Jan 03, 2013 at 03:30:14PM -0800, Andrey Jivsov wrote:
> >> Instead of 80 bit is security (birthday
> >> bounds) SHA-1 is listed as 51 bits on
> >> http://en.wikipedia.org/wiki/Message_digest.
> >
> > Since you mention the 51 bits part again and again ...
> >
> > Do you have any data / research underpinning this 51 (Besides
> > Wikipedia)?
> >
> > After all, the cited Wikipedia page links to the retracted variant of
> > an article :-(
> >
> > Otherwise, the best /theoretical/ result that I know of is just
> > above 60.
> 
> It looks like this is from the paper "Classification and Generation of 
> Disturbance Vectors for Collision Attacks against SHA-1"
> published in 2011 in Designs, Codes and Cryptography
> http://link.springer.com/article/10.1007%2Fs10623-010-9458-9?LI=true
> with 27 citations in Google scholar. There you can find a dozen of 
> different copies (or minor revisions?) of the paper and Wikipedia links 
> one of them.
> 
> Should we rather say that the _practical_ value is about 60 (it's not to 
> say that 2^60 is that practical, but that there is an expensive but an 
> actionable attack plan). The following post leads the reader to the 
> algorithm : 
> http://www.schneier.com/blog/archives/2012/10/when_will_we_se.html


In either case, humans are less than 2^33 todays and this number should not increase so much in the next decades. Even if each living human use OpenPGP and more than a dozen of keys, we are far from 2^60 or 2^51...

(even if we consider also the life expectancy)

regards,
-- 
jbar <[e-mail]>