[tahoe-lafs-trac-stream] [pycryptopp] #46: Add combined AES+XSalsa20 cipher module

[pycryptopp]

#46: Add combined AES+XSalsa20 cipher module
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Reporter:  randombit                             |          Owner:
    Type:  enhancement                           |  dragonxue
Priority:  major                                 |         Status:  new
 Version:  0.5.19                                |      Milestone:  0.7.0
Keywords:  xsalsa20 aes combiner design-review-  |     Resolution:
  needed                                         |  Launchpad Bug:
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Changes (by warner):

 * milestone:  0.6.0 => 0.7.0


Comment:

 Zooko and I looked at this one.. the IV argument needs work. Tahoe uses
 AES's IV= argument to perform random-access seeking through the keystream
 (since tahoe files are encrypted as one big block, but can be retrieved in
 little pieces, and we don't want to retrieve+decode+decrypt the whole file
 just for a short segment). Ticket #18 is about adding a cleaner "seek-to-
 offset" method or argument of some sort to AES. If we landed this combined
 AES+XSalsa20 as-is, its IV= argument couldn't be used as tahoe expects it,
 since the XSalsa20 side would interpret it differently. So we should
 probably:

  1: remove the IV= argument from this
  2: implement #18, adding a cleaner seek-to-offset API to AES
  3: implement the same API here in AES+XSalsa20
  4: when tahoe switches to use AES+XSalsa20, also switch to the new API

 Also, the patches (at least the .py file I looked at) have
 whitespace/indentation problems, and are importing an unused comb4p
 module.. we should probably run pyflakes over them.

 Zooko and I agreed to push this out of the 0.6.0 milestone and into 0.7.0.

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Ticket URL: <http://tahoe-lafs.org/trac/pycryptopp/ticket/46#comment:9>
pycryptopp <https://tahoe-lafs.org/trac/pycryptopp>