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[Pycrypto-checkins] [ pycrypto-Patches-1255031 ] do CTR mode in pure C
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From: SourceForge.net <no...@so...> - 2005-12-05 20:11:35
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Patches item #1255031, was opened at 2005-08-09 15:16 Message generated for change (Comment added) made by zooko You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=320937&aid=1255031&group_id=20937 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None Status: Open Resolution: None Priority: 5 Submitted By: Zooko O'Whielacronx (zooko) Assigned to: Nobody/Anonymous (nobody) Summary: do CTR mode in pure C Initial Comment: The design in which CTR mode calls a Python callable for each block is very flexible, but suffers an obvious performance cost. After these patches, one can optionally pass either a callable *or* a string of block length. If one passes a callable, then it functions as before. If one passes a string of length block length, then it makes a copy of the contents of the strings in an internal buffer, and increments that value in C for each block. This results in a nice speed-up, for example: AES: ECB mode: 90841.10 K/sec CFB mode: 2380.59 K/sec CBC mode: 68653.57 K/sec PGP mode: 70991.19 K/sec OFB mode: 69941.49 K/sec CTR mode: 1251.37 K/sec CTR mode, variable length: 1728.07 K/sec CTR mode, fast increment: 68122.18 K/sec CTR mode, fast increment (slow decrypt): 2367.85 K/sec That last line there is where it encrypts with the fast incrementer and decrypts with the Python callback incrementer to verify that the ctr increment is computed the same way. You can also browse and download these patches via my web view: https://yumyum.zooko.com:19144/cgi-bin/darcs.cgi/pycrypto-zookopatches/?c=patches There are three patches in the attached file. ---------------------------------------------------------------------- >Comment By: Zooko O'Whielacronx (zooko) Date: 2005-12-05 20:11 Message: Logged In: YES user_id=52562 Be sure and get the latest version from https://yumyum.zooko.com:19144/cgi-bin/darcs.cgi/pycrypto-zookopatches/?c=patches or http://zooko.com/repos/pycrypto or https://yumyum.zooko.com:19144/pub/repos/pycrypto-zookopatches/ since earlier versions of this patch had a bug so that it generated bad results if you crypted something that was not a multiple of block length and then crypted something else using the same cryptor object. See the unit tests or the patches for details. ---------------------------------------------------------------------- Comment By: Zooko O'Whielacronx (zooko) Date: 2005-08-17 15:27 Message: Logged In: YES user_id=52562 Okay, if you browse this patch server cgi script you can get the fix: https://yumyum.zooko.com:19144/cgi-bin/darcs.cgi/pycrypto-zookopatches/?c=patches Or just use HTTP to fetch the files from https://yumyum.zooko.com:19144/pub/repos/pycrypto-zookopatches As you can see there are a few other patches for testing and benchmarking in there. The benchmarking requires the pyutil library. The benchmarking shows that this backwards-incompatible change of eliminating the python callback and simplifying the code gives a speedup of somewhere between 0 and 4% depending on the exact usage. (You could also keep the speedup and keep the optional backwards-compatible Python callback support, but you can't keep all three of the speedup, the optional-backwards-compatible Python callback support, and the simpler code.) ---------------------------------------------------------------------- Comment By: Zooko O'Whielacronx (zooko) Date: 2005-08-17 12:07 Message: Logged In: YES user_id=52562 There's an issue in this patch -- it increments the counter before encrypting, so if you initialize the counter with 0 then the first block will be encrypted with 1. I'm fixing this issue, but my new patch is going to get rid of the optional Python callback entirely. (Maintaining both ways to do it is complicating things.) ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=320937&aid=1255031&group_id=20937 |
