SHA-1 Hash Collision Demonstrated – At Predicted Cost Levels

The research result on October 2015 from Dutch CWI did estimate that actual finding of two messages that collide producing same hash value will be possible in cost in order of $100 000. See our previous: SHA-1 is no longer considered secure.

Fresh result from same team with sponsored computing cluster capacity demonstrates that this is indeed correct cost estimate.

Actual Impact of SHA-1 Hash Collisions

The actual impact has not changed in past year and half:

  • Rapid challenge/response processing is safe because finding a collision takes at least hours, probably weeks or months.
  • Long term signature non-repudiation security depends on the value of that signature — if spending $100 000 is low enough cost for somebody to replace whatever is behind given signature, then that long term signature is not safe if it involves SHA-1 hashes.

Previously the cost level of producing this kind of hash collisions has been at levels of so called State Actors. This sub-million cost level is in corporate / criminal organization ball park. Meaning that organizations wanting to do this kind of things have just become a lot more numerous.

When Will SHA-1 Follow MD5?

Both algorithms are built on similar Merkle-Damgård construction, like is also SHA-2 family.

MD5 timeline:

  • MD5 hash algorithm was published in 1992.
  • First public collision was demonstrated in 2004 taking 1 hour in a computer cluster.
  • Collision break in less than 1 second in 2013 with single PC.

SHA-1 timeline:

  • SHA-1 hash algorithm was published in 1995
  • First public collision was demonstrated in 2017 taking a bit over 1 year of time with around 100 device years executed during it.
  • Public collision demo taking 1 hour or less time in ____ ?
  • Collision break in less than 1 second in ____ ?


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