Hi,

I made toughts also about this topic. My main problem is the following:

how do you synchronise the receiving and the transmitting stations? I. e.:
you take a sample, convert to digital, XOR with a key, send it. Then,
take the next sample, convert it to digital, and XOR WITH THE NEXT BYTE OF
THE KEY. Thus, it is necessary to use multibyte key, otherwise the enemy
could decrypt with brute force bcus he need only try 256 different
decrypting key. I suppose, if you use a multibyte key (e. g. 2048 byte or
so, or - better yet - you use two parallel running pseudo-random
generator), then the result would be like noise and the otherwise good
remarks of Mr. Holtz could be also eliminated.

I would interesting also on this project...

Regards,
Imre


On Wed, 5 Jan 2000, Don Holtz wrote:

> Just a thought about your XOR encryption:
>
> Are you trying the render the encrypted channel unintelligable?
>
> My gut feeling is that by using a simple byte-by-byte XOR method, the
> encrypted sound will still be very easy to undertand.  XOR does not alter
> the overall cadence, or frequency content of the sound very much.
>
> To do it properly it is best to distribute the sound energy in both time
> and frequency.
>
> You might want to test a quick implementation of your scheme on a PC
> first... to see how it works.... I would like to hear the results!
>
> Cheers,
> Don
>
> At 05:26 PM 1/6/00 +1100, you wrote:
> >Hello all,
> >I am interested in making a PIC based project in which I need to encrypt
> >voice. The voice is encrypted for transmission using a UHF radio.
> >Basically the person speaks into the microphone normally, the PIC samples
> >the analog data from the microphone at a minimum rate of 8kHz, XOR's it
> >with a preset 'key' and converts it back to analog for transmission. At
> >the other end the opposite is done. My question is does you run of the
> >mill ADC0831 8-bit ADC have what it takes to sample a voice signal?
> >
> >Wesley
> >
> >___________________________________________
> >Wesley Moore
> >RMIT - BEng/BApp.Sc. 2nd Year
> >
> >wmoore@cs.rmit.edu.au
> >http://wmoore.tsx.org/
> >
>
>