Quoting Mike Singer <mike@poluostrov.net>:

> >
> >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),
> .
> .
> .
> >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
>
>    Yes, the best way to keep your home secrets is to start asking
> every human on the planet how you should keep them, sending
> everywhere the return address.
>    Create your own simple and unique method based on real time
> clock for example. All this 007-agents will get crazy solving it,
> thinking you are using new super-dooper-brand_american-algorithm.

On the contrary, this is the proper way to do this, opposing this to the
myriad of el-cheapo-file-encryption-tools that you can find everywhere
on shareware sites.

I personnaly have done this kind of thing using DES as the encryption on
"Silver card II" devices (16F877 controllers + 24LC64 eeprom).
The trick to the system is that the program runs 2 modes.
The first mode is the "personnalise" procedure. This is the mode the card
comes in the first time after it is programmed. This mode allows for several
things to be set, such as the card's internal encryption key, stored in the
pic's internal eeprom.
The personalisation is started by a specific iso instruction which starts the
key generation procedure.
This procedure basicly takes a shitload of bytes sent by the host and generates
a key via some xor.
the bytes are generated from the system random generator

Then all data that is stored in the card is encrypted with the key via DES
before being written to the eeprom

Sincerely

Amaury

--

--
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