Bugtraq mailing list archives
Re: MD5 To Be Considered Harmful Someday
From: Jack Lloyd <lloyd () randombit net>
Date: Wed, 8 Dec 2004 14:19:27 -0700
On Tue, Dec 07, 2004 at 06:46:20PM -0700, Joel Maslak wrote:
The short-term fix seems to be something I've been recommending for a while: Compute hashes with both SHA-1 and MD5. The chance of one algorithm becoming compromised in the mid-term is relatively high IMHO (I was responsible for a PKI system which had to keep integrity for 20 year periods of time - not an easy task considering what we don't know about the future). The chance of two becoming compromised is relatively less. The chance of a problem with MD5 and SHA-1 allowing two different files to have collisions in both algorithms in *BOTH* is very very small.
You might want to read this: http://www.mail-archive.com/cryptography () metzdowd com/msg02611.html Essentially you can use Joux's attack to generate 2^64 collisions for SHA-1 with about 64*2^80 effort; out of those 2^64 collisions you have an even chance that at least one of them will also collide in MD5. That's still 2^86 hash computations, nothing to sneeze at, but nowhere near the expected 2^144 operations. That workfactor might be doable in a 20 year timeframe. It actually looks like it's better to generate 2^80 MD5 collisions instead of 2^64 SHA-1 collisions, since the initial collisions would be trivial to generate, and even if MD5 wasn't broken 80*2^64 + 2^80 << 64*2^80 + 2^64. So in fact you can generate a MD5||SHA collision with only a tiny bit more work than generating a SHA collision. So this really doesn't buy you anything. Jack
Current thread:
- Re: MD5 To Be Considered Harmful Someday, (continued)
- Re: MD5 To Be Considered Harmful Someday Solar Designer (Dec 13)
- Re: MD5 To Be Considered Harmful Someday George Georgalis (Dec 08)
- Re: MD5 To Be Considered Harmful Someday Dan Kaminsky (Dec 08)
- Re: MD5 To Be Considered Harmful Someday Ruth A. Kramer (Dec 08)
- MD5 To Be Considered Harmful Today Pavel Machek (Dec 08)
- Re: MD5 To Be Considered Harmful Today Dan Kaminsky (Dec 08)
- Re: MD5 To Be Considered Harmful Today Pavel Machek (Dec 08)
- Re: MD5 To Be Considered Harmful Today Dan Kaminsky (Dec 08)
- Re: MD5 To Be Considered Harmful Today Dan Kaminsky (Dec 08)
- Re: MD5 To Be Considered Harmful Someday Jack Lloyd (Dec 08)
- Re: MD5 To Be Considered Harmful Someday Jack Lloyd (Dec 08)