Dear Blue Boar, To be more precise, theoretically, if compare bruteforce with birthday, 160 bit birthday is equivalent to 81-bit bruteforce by calculation complexity (number of arithmetic operations).
I do not compare birthday vs bruteforce, I compare bruteforce vs bruteforce and birthday vs birthday. Practically, if you define some real values instead of mathematical symbols, software algorithm implementation and physical limitations must be also considered. Software implementation may be impossible or require more CPU cycles to implement algorithm with less arithmetic operations because, e.g. it requires more physical memory than you can address with 64bit integer :) --Thursday, March 22, 2007, 12:24:03 AM, you wrote to [EMAIL PROTECTED]: BB> My understanding that the kind of birthday attack under discussion would BB> start at 80-bits if SHA-1 (at 160-bits) were 100% secure. The attack BB> under discussion is reported to reduce that to the neighborhood of BB> 60-something bits. BB> I am not a mathematician though, so I would be perfectly willing to BB> believe I was wrong about that. BB> BB BB> 3APA3A wrote: >> Dear Blue Boar, >> >> It's not clear if this 'crack' cam be applied to birthday attack. My >> in-mind computations were: because birthday attack requires ~square root >> of N computations where bruteforce requires ~N/2, impact of 2000 times N >> decrease for birthday is ~64 times faster. 64 = 2^6. Because complexity >> is ~square root of possible combinations, it's equivalent of traditional >> birthday attack, with 160-(2*6)=148 bits hash (150 is my mistake in >> in-mind computations). >> >> Of cause, since I completely wasted 10 years after obtaining Master >> degree in Mathematics and 3 years after loosing last pencil I may be >> completely wrong in computations :) >> >> --Wednesday, March 21, 2007, 9:48:55 PM, you wrote to [EMAIL PROTECTED]: >> >> BB> 3APA3A wrote: >>>> I know meaning of 'hash function' term, I wrote few articles on >>>> challenge-response authentication and I did few hash functions >>>> implementations for hashtables and authentication in FreeRADIUS and >>>> 3proxy. Can I claim my right for sarcasm after calling ability to >>>> bruteforce 160-bit hash 2000 times faster 'a crack'? >> >> BB> Fair enough, your sarcasm tags didn't render properly in my MUA. I was >> BB> fooled by you stating that the birthday attack would be 150 bits. >> >> BB> BB >> >> -- ~/ZARAZA http://securityvulns.com/ Íó à â öåëîì, Óèëüÿì, çäåøíèé êëèìàò - åæåëè òîëüêî ýòî ìîæíî íàçâàòü êëèìàòîì, âïîëíå ñíîñíûé. (Òâåí) _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/