PDA

View Full Version : If there was no a5 encryption...



ekonomi
12-08-2003, 09:29 PM
Hello all,

I was wondering if there was no over air encryption through the a5 algorithm how would it be possible to make your mobile phone a scanner ?

I know that with netmonitor you can change channels in a cell but how can you "activate" the phone so that it would make the process of speech decoding and demodulation ?

If you could do that then you could propably listen all channels in the cell you are connected to, right ? tho i don't know what is going on exactly with the tdma. Meaning that I don't know if all that you have to do is activate the speech decoding and demodulation while you are in a channel that is used by another mobile phone, if that is correct then you could intercept it's session.

wumpus
12-08-2003, 09:43 PM
Mobile phones utilize frequency hopping during speech sessions, and you don't know the order the other phone uses, so scanning is impossible without a full-bandwith-scanner (instead of the single-frequency-one your phone is)

It would be possible to intercept things like SMS messages and special service requests though which go through one channel..

Too bad (well, good) the encryption exists and this is entirely hypthetical :)

ekonomi
13-08-2003, 08:01 PM
Correct me if I'm wrong but i think that the info about the frequency hopping algorithm is transmited through the Broadcast Control Channel (BCC) so the phone will follow the "hopping".

I don't know though if you can access the BCC transmited info without being recognised (if the info are transmited only to specific TMSI, so you won't have access if you don't have the proper TMSI).

Bleh! I thing it's over my head, and I'm jumping from an idea to another without examining all the possibilities hehe.

capotixplus
13-08-2003, 10:10 PM
Hey Ekonomi, contact me in private about it.... i'm working right now into it.

[email protected]