Protection against offline dictionary attack on static files

[Zooko Journeyman]

 Arcane Jill wrote:
>
<... a way to make decryption more expensive ...>

I think it is a neat idea.  I think it is best understood as a kind of 
"key-stretching" akin to iterated hashing of a password, as in:

Secure Applications of Low-Entropy Keys (1998)
John Kelsey, Bruce Schneier, Chris Hall, David Wagner 
http://citeseer.nj.nec.com/kelsey98secure.html

I invented it myself at one point, and then subsequently learned that it had 
already been published.  

Here are some notes I wrote about it earlier this year:

  """
  I've learned that Udi Manber, Martín Abadi [1], Mark Lomas, and Roger 
  Needham [2] have already published one of my ideas -- that of an extra "salt" 
  used to hash passwords, erased, and then brute-force-rediscovered when needed. 
  This kind of thing reassures me that my own part-time, self-directed crypto 
  research isn't too far off the mainstream. Manber's paper [3] is earliest, 
  but Abadi's [4] (published as a Technical Report) contains extra goodies such 
  as consideration of off-line brute force attacks on weak keys used in 
  communication protocols and a comparison to the more widely used key-
  strengthening of iterated hashing.  

  [1] http://www.cse.ucsc.edu/~abadi
  [2] http://research.microsoft.com/users/needham/
  [3] http://citeseer.nj.nec.com/manber96simple.html
  [4] http://www.cse.ucsc.edu/~abadi/Papers/pwd-revised.ps
  """

Regards,

Zooko

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