aes-586.pl

本代码是C语言实现的AES算法的源代码。AES是继DES之后目前最为流行的对称加密算法。

#!/usr/bin/env perl
#
# ====================================================================
# Written by Andy Polyakov <[e-mail]> for the OpenSSL
# project. Rights for redistribution and usage in source and binary
# forms are granted according to the OpenSSL license.
# ====================================================================
#
# Version 3.6.
#
# You might fail to appreciate this module performance from the first
# try. If compared to "vanilla" linux-ia32-icc target, i.e. considered
# to be *the* best Intel C compiler without -KPIC, performance appears
# to be virtually identical... But try to re-configure with shared
# library support... Aha! Intel compiler "suddenly" lags behind by 30%
# [on P4, more on others]:-) And if compared to position-independent
# code generated by GNU C, this code performs *more* than *twice* as
# fast! Yes, all this buzz about PIC means that unlike other hand-
# coded implementations, this one was explicitly designed to be safe
# to use even in shared library context... This also means that this
# code isn't necessarily absolutely fastest "ever," because in order
# to achieve position independence an extra register has to be
# off-loaded to stack, which affects the benchmark result.
#
# Special note about instruction choice. Do you recall RC4_INT code
# performing poorly on P4? It might be the time to figure out why.
# RC4_INT code implies effective address calculations in base+offset*4
# form. Trouble is that it seems that offset scaling turned to be
# critical path... At least eliminating scaling resulted in 2.8x RC4
# performance improvement [as you might recall]. As AES code is hungry
# for scaling too, I [try to] avoid the latter by favoring off-by-2
# shifts and masking the result with 0xFF<<2 instead of "boring" 0xFF.
#
# As was shown by Dean Gaudet <[e-mail]>, the above note turned
# void. Performance improvement with off-by-2 shifts was observed on
# intermediate implementation, which was spilling yet another register
# to stack... Final offset*4 code below runs just a tad faster on P4,
# but exhibits up to 10% improvement on other cores.
#
# Second version is "monolithic" replacement for aes_core.c, which in
# addition to AES_[de|en]crypt implements AES_set_[de|en]cryption_key.
# This made it possible to implement little-endian variant of the
# algorithm without modifying the base C code. Motivating factor for
# the undertaken effort was that it appeared that in tight IA-32
# register window little-endian flavor could achieve slightly higher
# Instruction Level Parallelism, and it indeed resulted in up to 15%
# better performance on most recent