extension of rsync on crypted files

Ben Escoto bescoto at stanford.edu
Thu Jun 27 08:34:06 EST 2002

>>>>> "MM" == mmikaelfr  <iso-8859-1>
>>>>> wrote the following on Thu, 27 Jun 2002 15:26:51 +0200 (CEST)

  MM> I am a french student and I have written a technical report on
  MM> an extension of the rsync algorithm to crypted files.  I started
  MM> from the situation of a client machine A user who doesn't wish
  MM> to save an original file v0 and its successive versions v1 v2 v3
  MM> ... on a distant server B but rather to save the private
  MM> ciphering of these files on the server. Let C be the cipher
  MM> algorithm and xi=C(vi) the ciphering of the clear file vi, the
  MM> client A wishes to save x0, x1, x2... on the server B and not
  MM> v0,v1.... This situation arrises for secured files backup
  MM> providers which offer an option of a secured and confidential
  MM> file's history backup - a client can keep the history of a file.

Sounds interesting.  Do you mean that the server holds multiple
versions of the file so older versions can also be restored?  Is this
done by storing checksum information about older files on the client?
Also, if I understood right, isn't this a bit different from rsync
since on the server you wouldn't see the files x0, x1, x2, ... but
rather the files x0, d1, d2, ... where d1 is a some kind of delta from
x0 to x1 (or I suppose an encrypted delta from v0 to v1)?  Or have I
misunderstood your system?

Ben Escoto
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