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Whales falling on houses - was: Hash collision count

From
Jon Seymour <jon.seymour@gmail.com>
Date
Apr 24, 2005, 22:25 UTC
Message-ID
<2cfc40320504241525c4153c2@mail.gmail.com>
In-Reply-To
<68ff9fa6050424142416fbadcd@mail.gmail.com>
.>
Show 9 quoted lines
> 1. Take your favorite text file, at least 160 characters long.
> 2. Choose 160 positions in this file.
> 3. For each position choose your favorite mispelling of that character.
> 4. Produce all 2^160 text files, all of the same length, choosing for
> each position either the original or the alternate character
> 5. Add an arbitrary file of the same length, different from the above
> 
> Two of these files have the same sha1 hash. Or, for that matter, for
> any 160 bit  hash the same is true.

If you were to create those files at 10^9 files per second, it would take you 10^38 years before you were in position to take step 5. I am about to turn 38 this week. Would that I could live to 10^38.

It's absolute rubbish to say that the best solution from an <double-quote>engineering</double-quote> point of view is to eliminate the infinitessimal possibility of a collision. Engineering is all about assessing risk and making suitable trade-offs. Every day of the week, "real" engineers accept life-threatening risks that put thousands of peoples lives in danger. They do it because we live in a world where risk cannot be eliminated, merely reduced to an acceptable level.

I can't understand that you are a prepared to drive a car or fly in a Boeing or Airbus that has a demonstrated risk of killing you, yet you want to insist on eliminating a risk that at most might create an interesting Slashdot headline: "Jolt-crazed programmer finds SHA1 collision - but later dies when whale falls on house".

jon.
-- 
homepage: http://www.zeta.org.au/~jon/
blog: http://orwelliantremors.blogspot.com/
Previous: Imre SimonNext: Tom Lord
Message 10 of 14 in “Hash collision count”
  1. Jeff GarzikApr 23, 2005
  2. Jeff GarzikApr 23, 2005
  3. Ray HeasmanApr 23, 2005
  4. Jeff GarzikApr 23, 2005
  5. Petr BaudisApr 23, 2005
  6. Jeff GarzikApr 24, 2005
  7. Petr BaudisApr 24, 2005
  8. Jeff GarzikApr 24, 2005
  9. Imre SimonApr 24, 2005
  10. Whales falling on houses - was: Hash collision countJon Seymour, Apr 24, 2005
  11. Tom LordApr 25, 2005
  12. Petr BaudisApr 26, 2005
  13. Ray HeasmanApr 24, 2005
  14. David LangApr 24, 2005

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