Re: Security for embedded device

From: Guy Macon (http://www.guymacon.com)
Date: 06/29/04 

Date: Tue, 29 Jun 2004 02:24:21 -0700

David Wagner <daw@taverner.cs.berkeley.edu> says...
>
>Joris Dobbelsteen wrote:
>
>>Does anyone know a simple cipher for a 8-bit processor with only a few bytes
>>of available memory, doing its job without about 1K cycles?
>
>Assuming you have some ROM: have you looked at Skipjack? DES? AES?
>Your performance goals sound quite aggressive. Almost certainly you
>will need at least 8 bytes of memory, merely to hold the key.

Joris, what do you mean by "simple cipher?" What is your threat model?

Is insuring that both ends have the same key a problem in your application?

I can give better advice if you tell me more about what you are trying
to accomplish.

I once did a very insecure "cipher" by simply filling up a block of ROM
with random bytes and looping through it XORing with the data to be
"encrypted." Trivial to crack, but my need was for a system where a
human eyeball looking at the "ciphertext" couldn't read it as it passed by. 

-- 
Guy Macon, Electronics Engineer & Project Manager for hire. 
Remember Doc Brown from the _Back to the Future_ movies? Do you 
have an "impossible" engineering project that only someone like 
Doc Brown can solve?  My resume is at http://www.guymacon.com/

Relevant Pages

  • Re: maybe a bit OT: EEPROMs and PCs
    ... | Ahh, okay. ... | BIOS chips. ... For all ROM code I'd use ... The things inbetween these brackets are the memory address. ...
    (alt.lang.asm)
  • Re: Self booting systems with out bootloader?!!!
    ... A non-fragmented memory just means that every byte from the start of memory ... This means that after a reset is made, ... in processor ROM. ... executing the 'work program'. ...
    (comp.arch.embedded)
  • Re: ZX Spectrum - cant get it repaired - help!
    ... Swapped ROM (not 100% usre if that one works, ... o All 4116 RAM's are 100% ok; all connections were checked, ... sound A and after a second or so, it makes sound B and it keeps sound ... It`s been a long time, but I used to repair Spectrums regularly, and what you describe is symptomatic of one of the memory ic`s being faulty, have you tried it with the 32k extension removed? ...
    (sci.electronics.repair)
  • Re: Installing applications in ROM WM 2003
    ... "Also you should be aware that generally WM5 devices will be slower than ... PPC 2003 devices because of the different way that they use memory." ... To my mind you want features that your hardware just doesn't support. ... has been able to interpret the BIN images that seem to make up the ROM ...
    (microsoft.public.pocketpc)
  • Re: Motorola MPx300
    ... You should have two types of memory, ... Storage and Program, and may have a bit of control over how they are ... Program side of RAM is what you and the OS need to run programs. ... is there any way to delete ROM? ...
    (microsoft.public.pocketpc)