Phone Call Security

Matthew S. Hamrick mhamrick at
Mon Jun 4 18:08:24 CEST 2007

No.. as far as I know, the encryption is an integral part of the  
protocol. Though Martin Tomasek tells me he's seen carriers that  
don't operate with encryption turned on. But in any event, I'm pretty  
sure that if the network does GSM encryption, your phone can't  
request a non-encrypted channel. But as far as the authentication and  
encryption goes, it doesn't add terribly to the latency and only  
slightly to the bitrate.

In the US, at least, you wouldn't be able to sell a service like this  
as it would make it impossible for the carrier to comply with CALEA.  
I don't know about other countries, but I suspect every nation's  
intelligence services would be loathe to give up the ability to tap  
individual calls at will. (Which is one of the reasons that some  
people find end-to-end encryption interesting in the first place.)

-Matt H.

On Jun 4, 2007, at 1:07 AM, Pander wrote:

> Matthew S. Hamrick wrote:
> ...
> Could it be possible to have you GSM request a non-encrypted  
> channel? Would this channel provide more bandwidth or less delay  
> because of that? If so, the extra bandwidth or reduced delay could  
> be used for efficiently using your own encryption.
> Can anyone elaborate if this is possible with the current network  
> hardware and GSM service providers? If this is possible, that could  
> mean a new service for the GSM service providers: network  
> subscriptions which you can choose per connection to have network  
> encryption enabled or not. Your telephone could e.g. automatically  
> disable it when you are calling with someone which has a telephone  
> supporting the same end to end encryption as yours does.
> Regards,
> Pander
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