Hi Ricardo

That's an interesting concept!

I wonder if the MMS propagation time would be an issue for using it in a PTT 
scheme like this?

In the country I am in. It can be a matter of dozens of seconds, possibly even 
low minutes before MMS delivery occurs depending on network load. I am assuming 
they are store & forwarded by a server somewhere on the carrier's network.

Still, it's a pretty neat 'outside the square' type idea :)

Pete


On 18/11/2015, at 2:13 AM, Ricardo Andere de Mello <[email protected]> 
wrote:

> Hi,
> 
> I have thought several times about a secure GSM phone, and one thing that I 
> paticularly dont like is the fact that GSM phones, even if connected through 
> audio jacks or bluetooth mics, can still operate in a non secure way.
> The the GSM module firmware is usually not open, and they can in theory open 
> the internal mic to hear us at any time.
> 
> So... my idea is pretty simple. why DO NOT HAVE MIC AT ALL?
> If you use a GSM raw module, you dont need the mic, speaker, and all audio 
> stuff.
> 
> ok... so... how to transmit the data if we dont have a mic?
> 
> just use encrypted codec2 payloads over MMS. :)
> MMS supports at minimum 300kb (enough for push-to-talk conversation)
> At the same time, both ends would be encrypted, and this is the best 
> encryption system I can think since it is totally under your control.
> 
> If you need some help with this, drop me a line.
> 
> []s, Ricardo Mello
> 
> 
> 2015-11-12 11:02 GMT-02:00 Nouman Khalid/A-XEN R&D/NRTC 
> <[email protected]>:
> Hello List,
>                        I am working on sm1000 for secure gsm phone project 
> just like jackpair. I initially learned to work in the LINUX environment and 
> built some basic codes for sm1000 and tested them. Then I built sm1000 
> firmware of codec2 and tested it successfully. As far as gsm phone is 
> concerned, is it possible to connect sm1000 with gsm phone directly as 
> jackpair is doing? I am asking this because mobile phone will also use its 
> own codec for compression and if we apply an already compressed voice on 
> audio jack of mobile phone; will it be able to retrieved as encryption will 
> be added in FreeDV mode?  Please guide me how I can make sm1000 work in full 
> duplex mode?
> 
> 
> Thanks and Regards
> Nauman Khalid
> Assistant Executive Engineer
> Research & Development – NRTC, Pakistan
> Phone: +92-995-666-646/634
> Mobile:+92-3008098569/+923208098569
> Email : [email protected]
> Web : www.nrtc.com.pk
> 
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