Cracking 14 Character Complex Passwords in 5 Seconds • Hacker News Board

Re: Cracking 14 Character Complex Passwords in 5 Seconds

#61

Post by tptacek » Sun, Oct 31, 2010, 4:42 PM UTC

_b8r0 wrote: post #51

tptacek wrote: post #37

Earlier quoted context omitted.

You say "definitely the best crypto flavor" as if you knew. But you don't, because no serious system designer cares about rainbow tables. Unix solved this problem in the nineteen seventies . Real system designers care about incremental crackers, of the sort used since the 1980's to harvest thousands of passwords from compromised Unix boxes, of the sort that forced Unix systems in the 1990's to adopt "shadowed" passwo…

Are you saying that we should ignore rainbow tables? I appreciate that you know way more about crypto than I do, but I think you're working from the standpoint that people know how to do things the right way, as opposed to the real world situation where people very clearly don't (e.g. NTLM, Oracle being 'Unbreakable', iPhone screen lock security mechanisms). For as long as there's people using unsalted MD5 hashes in…

Yes. I think you should ignore rainbow tables. People using salted MD5 hashes in their PHP applications are also creating a real threat.

Re: Cracking 14 Character Complex Passwords in 5 Seconds

#62

Post by _b8r0 » Sun, Oct 31, 2010, 5:19 PM UTC

tptacek wrote: post #60

dstorrs wrote: post #52

Earlier quoted context omitted.

> Unix solved [the problem of rainbow tables] in the nineteen seventies. > incremental crackers [were used to] harvest thousands of passwords [and] forced Unix systems in the 1990's to adopt "shadowed" password files. As someone who is interested in security but has not spent significant time studying it, I'd be interested to hear more about this. How did Unix solve the rainbow table issue? What is an incremental cra…

The original Unix crypt(3) password scheme invented (and coined the term for) salts. Incremental password crackers, like John the Ripper and Crack, take a single password hash, and an actual dictionary, and hash each entry in the dictionary looking for a match. They take days to run instead of seconds, and until people started wanting to break into Windows boxes, they were the only way people cracked passwords.

They don't take days to run. The other week I cracked around 16,000 LM hashes with EDPR in about 6 hours.

Incremental crackers have improved substantially over the past few years primarily due to the introduction of GPU programming (in some cases algorithms port easily, in other cases they need some work first to be optimal on a GPU), easier distributed programming and rainbow tables. There's some interesting projects that use GPU technology to optimise the rainbow table reduction function (see http://www.cryptohaze.com/ for an example). As GPU technology improves and as hardware becomes cheaper and more powerful these technologies bring capabilities previously limited to three-lettered agencies into the commercial and home space.

Re: Cracking 14 Character Complex Passwords in 5 Seconds

#63

Post by peterwwillis » Mon, Nov 01, 2010, 3:29 PM UTC

mrb wrote: post #14

peterwwillis wrote: post #8

People, NTLM hashes have been dead for years. Stop using them. http://support.microsoft.com/kb/299656

You are confusing NTLM hashes with LM hashes. The article you point to is about LM hashes, not NTLM hashes. There is no way to stop using NTLM hashes on Windows.

Yes, the article I point to is concerning LM hashes, but NTLM hashes are almost as bad - and you can stop using them.

This URL shows you how to force NTLMv2: http://windows-secure.net/O.Reilly-Securing.Windows.Serv/059...

The idea is to try to force Kerberos authentication only. I can't find any tips on forcing it explicitly (even through group policies) but perhaps there's a firewall method to disable any [NT]LM auth and only allow Kerberos auth. I think some specific services may only allow NTLM (such as Telnet) and some services (such as IIS) may have to explicitly be configured to use Kerberos.

(edit) I should mention that I am not an expert on configuring Windows domains or their authentication (obviously) but according to some random guy I asked in IRC, if the SPN is set on a calling ID for a given service, Kerberos will always be used (or attempted anyway) and enabling TCP instead of UDP for the communication may help it get through firewalls etc (and solve some other login-related problems with UDP attempts). However, I think NTLM is the only one that can get through all manner of proxies, firewalls, etc (for IIS for example).

Re: Cracking 14 Character Complex Passwords in 5 Seconds

#64

Post by yuhong » Sat, Nov 13, 2010, 1:08 AM UTC

peterwwillis wrote: post #63

mrb wrote: post #14

Earlier quoted context omitted.

You are confusing NTLM hashes with LM hashes. The article you point to is about LM hashes, not NTLM hashes. There is no way to stop using NTLM hashes on Windows.

Yes, the article I point to is concerning LM hashes, but NTLM hashes are almost as bad - and you can stop using them. This URL shows you how to force NTLMv2: http://windows-secure.net/O.Reilly-Securing.Windows.Serv/059... The idea is to try to force Kerberos authentication only. I can't find any tips on forcing it explicitly (even through group policies) but perhaps there's a firewall method to disable any [NT]LM aut…

BTW, don't confuse hashes with authentication protocols. There is no such thing as an "NTLMv2 hash". NTLMv2 is an authentication protocol, and NTLM and LM are authentication protocos too. There is the LM hash and the LM authentication protocol dependent on it, of which both is insecure, but are two different things.