target collisions and colliding certificates with different identities

[Weger, B.M.M. de]

Hi all,

We announce:
- an example of a target collision for MD5; this means: 
  for two chosen messages m1 and m2 we have constructed 
  appendages b1 and b2 to make the messages collide 
  under MD5, i.e. MD5(m1||b1) = MD5(m2||b2);
  said differently: we can cause an MD5 collision for 
  any pair of distinct IHVs;
- an example of a pair of valid, unsuspicious X.509 
  certificates with distinct Distinguished Name fields, 
  but identical CA signatures; this example makes use 
  of the target collision.

See http://www.win.tue.nl/hashclash/TargetCollidingCertificates/,
where the certificates and a more detailed announcement 
can be found.

Marc Stevens
Arjen Lenstra
Benne de Weger

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