why we can not !!

[JohnnyGalaga]

I believe you are right but I'm not 100% sure. I do know that there are two ciphers used depending on the country. A51 is the stronger of the two while A52 is the weaker.

The encryption is setup between the base station (rbs) and the mobile equipment (me).

With a proper test set, you can actually decode the audio frames right at the base station.

Half rate channels are available which I guess could be considered a form of compression. With the new adaptive multi rate vocoders, half rate audio doesn't sound half bad and is starting to be implemented on busy sites.

So the encryption key is transmitted over the air? Wouldn't a hacker then be able to get it and decode the audio? How does the phone and the tower know which frequency to send information back and forth on?

Oh, and what is "half rate audio" ?

 

[nd5y]

The cell site tells the phone what frequency to use. Each cell site broadcasts a control channel which contains among other things a list of neighbor cells and your phone checks the neighbor cells' signal strength periodically when it is idle and also during the unused time slots when you are talking on it.

 

[nd5y]

Here is a web site that explains how GSM encryption works
http://www.gsm-security.net/faq/gsm-encryption.shtml

 

[JohnnyGalaga]

Interesting. How does the phone know what the control channel frequency is to begin with?

 

[nd5y]

When you first turn the phone on it scans for the strongest control channel

 

[nd5y]

Your phone is programmed to look for control channels on the bands, frequency blocks, annd network IDs that your phone company uses. If it doesn't find a control channel with your network ID it then looks in other bands and frequency blocks for network IDs of other carriers that have roaming agreements with your carrier.

 

[N_Jay]

Interesting. How does the phone know what the control channel frequency is to begin with?

Time to do some READING instead of asking people to spoon feed you all the answers. :wink:

 

[JohnnyGalaga]

Sometimes it's easier to simply ask then to spend hours searching and reading.

ASS.

 

[10-95]

-?---------------------------------------------------------------------------

 

[nd5y]

Sometimes it's easier to simply ask then to spend hours searching and reading.

If you DON"T spend hours searching and reading you might not be able to tell when somebody is just feeding you BS.

 

[Al42]

Cellular phones have, among other things programmed into them, a default cell to use as a control channel.

 

[N_Jay]

Sometimes it's easier to simply ask then to spend hours searching and reading.

ASS.

I did not say being spoon fed was NOT the easier way.

It's just not the BETTER way.

 

[morfis]

Cellular phones have, among other things programmed into them, a default cell to use as a control channel.

How would that work? I switch my phone on at O'Hare and it works....why would it have a default cell programmed in for there when it is a UK phone?
Works fine everywhere else I've needed it outside the UK...can't have a default cell set up for every possible location in the world?

 

[steve_eg]

How would that work? I switch my phone on at O'Hare and it works....why would it have a default cell programmed in for there when it is a UK phone?

One big-a$$ smartzone network? HAHAHA


Seriously, does anyone else see a problem with the origins of this thread, or am I just overly mistrustful?

 

[morfis]

One big-a$$ smartzone network? HAHAHA


Seriously, does anyone else see a problem with the origins of this thread, or am I just overly mistrustful?

I see no problem with the origins except that the subject has been done to death on just about every scanning forum in Europe and then again in the USA. A web search will yield all the info needed to say that a normal scanner won't get you a decode of GSM telephones. It will also yield several sites where people are selling snake oil.

Foe his next question he'll probably ask about listening to encrypted TETRA radios.

All the thread proves is that most people starting such threads don't bother to look at FAQs, WIKIs or search engines?

 

[WayneH]

PEOPLE, please, stay on topic. It's not that difficult of a thing to do.

No, not all of you but the minority with SAS.

-Wayne

 

[mikewazowski]

How would that work? I switch my phone on at O'Hare and it works....why would it have a default cell programmed in for there when it is a UK phone?
Works fine everywhere else I've needed it outside the UK...can't have a default cell set up for every possible location in the world?

No, they don't have a default cell programmed in.

What they do have is a default (preferred) network to search for first before trying other networks. Generally the Sim has a list of networks that the provider has roaming agreements with. If none of these are available then it will grab the strongest network.