In the wake of an embarrasing and very public display of misdeeds by Detroit mayor Kwame Kilpatrick, I immediately understood the importance of data encryption. Especially, when the information could be official government business or a personal piece of text that you do not want anyone but the recipient to see. I suppose the problem with the current SMS model is that the ILECbehave as a proxy for all information that passes through their servers. So by law, if say AT&T was subpoened for police officials, they would be inclined to give up the data. That simply is bad business. However, what if you could erect your own proxy before the data ever reached their servers?
From my limited knowledge of SMS, I believe it contains similar message headers to that of email. So, I imagine that encryption methods like GPG would suffice to prevent clear text SMS transmissions.
Recently, I was doing a bit of debugging with my ekiga softphone. Running the application with the following flag 'ekiga -d 4 ' revealed all of the message headers associated with initiating a VOIP conversation the To and From headers are very similar to SMTP headers. The ACK and INVITE headers were also quite familiar.
Phil Zimmermann's ZFone application encrypts VOIP traffic quite easily. More accurately, all VOIP traffic that uses established RFC standards. ZFone does not encrypt Skype traffic because Skype does not use SIP or any other industry standard protocol.
I will be looking for an SMS encryption method, you should too..