is DES Faster Than AES on software I conducted a software based experiment for encrypting difference size of images using AES and DES. However unexpectedly DES encryption speed was higher than AES. is it possible that DES is faster than AES?. I also search the literature but could not come up with clear conclusion on this matter. Thanks
Yes, it is possible that AES is slower than DES. There is no limit to the slowness of un-optimized software!

Some factors that I have witnessed slowing a software AES implementation:


not using tables for computation of the S-box(es) (an extreme example is the implementation there, when compiled with BACK_TO_TABLES undefined; another possibility is using a formula intended for hardware or bitslicing, perhaps in order to remove timing variations).
using hexadecimal ASCII (or binary) strings for everything, perhaps with the excuse that there is no built-in 128-bit type;
using an interpreted language (one without built-in XOR will insure particularly poor performance)
leaving debug code that dumps every intermediary result, even if that's effectively to /dev/null or equivalent;
to a moderate degree, recomputing subkeys at each invocation when the mode of operation allows to factor that out;
to a small degree, using 256-bit keys (it is hard to lose more than a factor of two with this one).


This is also applicable to DES to a large degree.

I should have mentioned that for decently and comparably optimized implementations, AES is typically faster than TDES and often than DES, and illustrated that with throughput; but that other answer does it nicely.