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Re^2: MD5 - what's the alternative

by beable (Friar)
on Aug 27, 2004 at 08:22 UTC ( #386283=note: print w/replies, xml ) Need Help??

in reply to Re: MD5 - what's the alternative
in thread MD5 - what's the alternative

I don't understand why you think limiting the length of plaintext passwords to say, 12 to 16 characters will mitigate or eliminate the threat. Surely all that would do is reduce the search space that the attacker has to try to find a matching MD5 hash, making it even easier and quicker to crack the system. That's unless you think that the attacker won't know that you are limiting password length, in which case, aren't you relying on "security through obscurity"? As we all should know, security through obscurity gives a false sense of security, rather than actual security.

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Re^3: MD5 - what's the alternative
by fergal (Chaplain) on Aug 27, 2004 at 09:55 UTC
    I think the idea is that if you want to find THE 16 character plaintext it takes 2^128 operations. The new vulnerability means you can find an equivalent (but longer) plaintext in 2^40. So if you limit the password to 16 characters then a longer plaintext with an identical hash is no use. That said, I could be completely wrong about the vulnerability always producing longer strings.

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