Of *course* the PIC can do the RSA algorithm.  Heck, you can decode MP3s
on the PIC, and even do raytracing.

The question is how fast do you want to process this data?  It sounds to
me like a computer dongle.  I hope not, I hate those things.

But if that's all it is then you can probably expect to be able to do a
fairly complex (higher bit) RSA on a several byte word in a second or
so.  If cost is not an issue then use a PIC with a single cycle 8x8
multiply.  Better yet, use the new DSpic (samples coming to a supplier
near you... maybe...Real Soon Now(tm)) which has a nifty multiply and
accumulate (among other things) instruction which simplifies just these
kinds of tasks.

Make sure that whatever data you're sending changes every time and is
not guessable - put a semi-random counter value in, the time, current
temperature, maybe a stream of ones and zeros from a noisy transister
(why don't they put a noisy transister inside the PIC as a peripheral?
 Make it rotate into a register that can be accessed as an 8 bit random
value?  It wouldn't be completely random, but it couldn't take up that
much die space and will be better than a PRNG...  )

-Adam

Werner Soekoe wrote:

>Hi everyone.
>
>I'm trying the impossible. I want to design a circuit using a PIC16F84 that transmits data to a computer. I want this data to be encrypted, however. I've been looking into using RSA encryption (as low as 32-bit), but I can't imagine the F84 handling these kind of calculations (32bit value to the exponent of another 32bit value). The idea was to have it work like this:
>
>PIC = PIC based circuit
>COMP = Host Computer
>
>PIC -> COMP : Hey, I want to send data!
>*COMP* : Computer generates random public and private keys
>COMP -> PIC : OK. Here is a public key to use.
>*PIC* : Encodes data with public key
>PIC -> COMP : Here is the encrypted data
>*COMP*: Decrypts the data using private key
>COMP -> PIC : Thanks, the data was decrypted and valid
>
>Then repeat the process as required.
>
>Does anyone have any better idea of an encryption/decryption method to use? The basic idea is just to be able to transmit data without anybody tapping into the physical wire being able to see what's being transmitted.
>
>Thanks!
>
>Regards,
>Werner Soekoe
>WernerS@fsl.gov.za
>
>--
>http://www.piclist.com hint: The list server can filter out subtopics
>(like ads or off topics) for you. See http://www.piclist.com/#topics
>
>
>
>
>

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics