[Libaes-devel] PowerPC G4 AES implementation

[Rickard H. <Ric...@st...>]

Hello everyone (still only Nigel and Sandy?)

I have written a vector-based implementation of AES in PowerPC G4 
assembler (there is an alpha version at 
http://home.student.uu.se/riho7361/aes.html). Since the PowerPC has 
pretty bad memory performance, I chose not to use any look-up tables 
other than the s-box and its inverse, and put that in registers (filling 
half of the available 32 x 128 bits vregs). This means that I have a 
quite high latency for loading the s-box, generating constants, etc. 
When that is done, encryption and decryption is quite fast. Thus, it is 
quite slow to encrypt a single block and much more efficient to encrypt 
more blocks in a single function call, since it only has to set up the 
constants once for each call. The PowerPC probably isn't the only 
processor where it would be beneficial to have an API that can process 
several blocks in one call. It could also be quite well-suited to wrap 
CBC and other modes of operation, if that should be included in the 
library.

	/Rickard Holmberg