[Ocf-linux-users] why aes algorithm faster than null algorithm when running cryptotest using cryptosoft?

[da x. <xia...@gm...>]

when I test ocf,I found this strange problem.I use:
linux-2.6.26.8
crypto-tools-20080917
ocf-linux-20080917
openswan-2.6.16

#
# OCF Configuration
#
CONFIG_OCF_OCF=y
CONFIG_OCF_RANDOMHARVEST=y
CONFIG_OCF_CRYPTODEV=y
CONFIG_OCF_CRYPTOSOFT=y

to run the test,I get the result:
./cryptotest -a null 256 8192
   0.067 sec,     512   null crypts,    8192 bytes, 63046643 byte/sec,
481.0 Mb/sec
./cryptotest -a aes 256 8192
   0.036 sec,     512    aes crypts,    8192 bytes, 117038368 byte/sec,
892.9 Mb/sec
./cryptotest -a md5 256 8192
   0.008 sec,     256    md5 crypts,    8192 bytes, 272215992 byte/sec,
2076.8 Mb/sec
./cryptotest -a des 256 8192
   0.078 sec,     512    des crypts,    8192 bytes, 53531550 byte/sec,
408.4 Mb/sec
./cryptotest -a 3des 256 8192
   0.225 sec,     512   3des crypts,    8192 bytes, 18631166 byte/sec,
142.1 Mb/sec
./cryptotest -a sha1 256 8192
   0.023 sec,     256   sha1 crypts,    8192 bytes, 90045170 byte/sec,
687.0 Mb/sec

why aes and md5 are so faster than null algorithm?