C[omp]ute

From: "andrew cooke" <andrew@...>

Date: Sun, 26 Mar 2006 10:54:57 -0400 (CLT)

I don't understand this, but it looks ominous:

  In this paper we introduce a new idea of tunneling of hash functions. In
  some sense tunnels replace multi-message modification methods and
  exponentially accelerate collision search. We describe several tunnels
  in hash function MD5. Using it we find a MD5 collision roughly in one
  minute on a standard notebook PC (Intel Pentium, 1.6 GHz). The method
  works for any initializing value. Tunneling is a general idea, which can
  be used for finding collisions of other hash functions, such as SHA-1, 2.
  We show several capabilities of tunnels. A program, which source code is
  available on a project homepage, experimentally verified the method.

http://cryptography.hyperlink.cz/2006/Tunnels.pdf
http://cryptography.hyperlink.cz/MD5_collisions.html

Especially - to what extent is this specific to MD5 (already known to be
weak), and to what extent is it general?

Google turned up this discussion - http://technocrat.net/d/2006/3/21/1500
- which included:

  From a cursory examination it appears that this method generates two
  different pseudorandom pieces of data which have the same md5sum hash
  output.

  They have not shown an easy way of generating an alternative set of
  data with the same md5sum as a chosen file or to generate a collision
  for a chosen m5 hash.

  This means that common uses of md5 are not yet broken. For example
  schemes to check the authenticity of files such as verified links for
  filesharing programs or using a hash value from a trusted source to
  check that a software download has not been modified.

Andrew