DYI Landline Encryption

[s25]

That would be the most logical approach Bohrium.

[TheFallen]

Thats true, you could dump the data on a txt file on a flash drive, 128mb's are about £5 or less these days, and read it from there. i'd be fairly easy to write the code to pull up info from a file (I'm learning this at uni now) and it'd save having to add it all on to the device via a keyboard and screen.

I'd think this project is definately possible, but rather complex.

[Bohrium]

I've got the crystals, the appropriate microcontrollers, and the rest of the components. Now to start the coding!

[TheFallen]

wait, to pull data off of a USB key the device would need to be a controller, which is not easy at all to do. Much better to use something like an SD card.

[nme]

Right tell me if I'm understanding this correctly..
Are we talking about just having two paired keys? I'm not too big on programming and microcontrollers etc. If it were a constantly changing encryption I suppose you would need like an initiation signal Or something the receiving end would recognise, But once they've made a connection the transmitting end could simply tell the receiving end where to look for the next package of data (Location generated at random). I'm thinking largely along the lines of Digital Frequency hopping. I imagine interference might be a b*tch though.
Or if the encryption were fixed; at the start when opening the channel The transmitter would generate a random new 'alphabet' and send it to the receiver. Then the receiving end would follow the 'key' given at the start for the remainder of the phone-call. This wouldn't be as secure but would probably do one phone-call assuming a new 'alphabet' is generated each call. However it would be important that the receiver recognise the 'alphabet'/'key'/'legend' and respond accordingly, something only paired keys could do. Or are you saying have a programmed fixed 'alphabet' that the paired keys would follow everytime?
Sounds fun Might have a go myself sometime over the next long holiday. It's definitely within reach!

[TheFallen]

The way I saw it was you'd speak, this would get sampled (converted to digital data), you'd have that stored in a buffer, as the buffer got filled, you'd then use the GPG algorithm to encrypt it using your keys. and then at the other end it would be decrypted, and played back.

As for the protocol handshaking, that can be very easily done, after all, it's not too dissimilar to a modem, like a 56.6k or a DSL one.

The hardware can easily be dropped in, Even easier would be to have a PC and avoid micro-controllers completely.