Date: Tue, 18 Aug 2015 23:39:15 +0200 From: magnum <john.magnum@...hmail.com> To: john-dev@...ts.openwall.com Subject: Re: 7z's KDF is unsalted On 2015-08-18 23:25, Solar Designer wrote: > On Tue, Aug 18, 2015 at 10:59:43PM +0200, magnum wrote: >> On 2015-08-18 10:52, magnum wrote: >>> On another note, it seems 7z is actually unsalted within the KDF. So one >>> could make extremely effective Rainbow tables for it. >> >> Issue #1679, PR #1681. > > I went to: > > https://github.com/magnumripper/JohnTheRipper/issues/1679 > > and there you mention similarity to WPA-PSK. But we don't have this for > WPA-PSK: BTW I dropped that comment before reading this. > [solar@...er run]$ GOMP_CPU_AFFINITY=0-31 ./john -test -form=wpapsk > Will run 32 OpenMP threads > Benchmarking: wpapsk, WPA/WPA2 PSK [PBKDF2-SHA1 128/128 AVX 4x]... (32xOMP) DONE > Raw: 10645 c/s real, 334 c/s virtual > > ... or do we? And folks are generating per-SSID rainbow tables for > WPA-PSK, treating it as salted for that purpose. For WPA-PSK the SSID is the salt (and we do take advantage when possible). For 7-zip the KDF is completely unsalted. You won't see the boost in WPA-PSK benchmarks but in real cracks against same-SSID pcaps. I guess we could add a same-SSID test vector to WPA-PSK to show the boost but it's not as fair a figure. > And doesn't the AES step prevent rainbow tables for 7-Zip (even if it > doesn't prevent the speedup you've now implemented)? I'm not quite sure. Does it? It's a later step, just like the post-processing for WPA-PSK. magnum
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.