[RFC][PATCH 1/2] Twofish cipher i586-asm optimized

[Joachim Fritschi]

Implementation:
-----------------------
This code is based on the current linux twofish cipher c implementation. Only 
the decrypt/encrypt routines were replaced by optimized assembler code. The 
in-kernel code by Matthew Skala takes care of the keysetup and precomputation 
of the sbox lookup tables.
I have tried to cut down stack use to a minimum (1 push/pop per round) and 
optimize the code as much as possible. The patch is similar to the existing 
aes assembler implementation.

Testing:
-----------
The code passed the kernel test module and passed automated tests on a 
dm-crypt volume reading/writing large files with alternating modules ( c / 
assembler ) and comparing results.

Benchmarks:
-------------------

Performance on a dm-crypt volume increased about 30% while reading. With 
256bit keylength it even outperformed the 128bit aes assembler code.

http://homepages.tu-darmstadt.de/~fritschi/twofish/output_20060417_185029_x86.html

The write performance in this benchmark was limited by the harddrive and not 
the algorithm / system speed. Any suggestions how to benchmark the overall 
speed accurately are welcome.


Patch:
----------

http://homepages.tu-darmstadt.de/~fritschi/twofish/twofish-i586-asm-2.6.17.diff


Please have a look, try, improve and criticise.

Regards,
Joachim



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