Vitaliy escreveu:
> Isaac Marino Bavaresco wrote:
> --------------
> I use AES (128-bit symmetric key cryptography) with authentication, so
> nobody else can upload anything to my hardware.
> --------------
>
> Do you think the standard Microchip libraries are good enough to use in a =

> simple bootloader?
>
> http://ww1.microchip.com/downloads/en/AppNotes/01044a.pdf
>
> I'm not familiar with the AES algorithm, what would be the penalty in goi=
ng =

> from 128-bit to 256-bit encryption, in terms of execution speed and code =

> size?
>
> Vitaliy
>   =

I wrote my AES routines based on the Microchip's Application Note (don=B4t
remember the number) for PIC16 MCUs (assembly language).

I ported it to Hi-Tech PICC, Hi-Tech PICC-18 and MPLAB-C18 (all for asm
and C) and MPLAB-C30 (asm only).

In a PIC16 MCU it can encrypt one 16-byte block in less than 1ms @ 20MHz
(600 micro-second +-).
Decryption is somewhat slower.

Uses some FLASH though (over 1K word). And about 40 bytes RAM.

To go 256-bit may triple the time (2 x key size x 40% more rounds). Must
test.

__________________________________________________
Fa=E7a liga=E7=F5es para outros computadores com o novo Yahoo! Messenger =

http://br.beta.messenger.yahoo.com/ =


-- =

http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist