Android Question Securing a phone call

[udg]

Hi all,

sorry for the eye-catching subject, a probably too high goal to achieve for me at the moment.
What I'd really like to do is letting two parties have a conversation over Internet using some sort of data stream passing through a cryptographic function.
A server will be needed to exchange current IP and serve the public part of the other party certificate in order to make the packets "secure".
So my app should be able to connect to a server where to find my friend's current Ip (if he's actually connected) and his public sign, then use local mic to capture my voice, break it in chunks and use a crypto-function to encode the chunks with my private sign and my friend's public one, then send out the "stream" over Internet to my buddy's phone where everything is reversed in order to let him hear my original message.
A walkie-talkie conversation is acceptable.

Any ideas or hints on how to achieve the above? TIA

Umberto

 

[Erel]

You cannot connect two devices directly over the internet. The data will need to be sent to the server and then to the other device.

 

[udg]

Hi Erel, thank you for your reply.
Do you think it will be feasable, altough very difficult, to do something similar but within a regular GSM phone call?
The schema could be:
1. look up on a server for the crypto data needed
2. establish a regular phone call
3. intercept what is captured by your mic and send it in chunks to a crypto-function
4. trasmit the result of the crypto-function over the voice channel established at point 2

I understand the overhead of the crypto should be kept at a minimum and the conversation probably will not be as fluent as a regular one, but can it be done? Or simply there's no way to "read" the mic and then transmit those data (even unchanged) over the GSM call?

Umberto

 

[LucaMs]

You cannot connect two devices directly over the internet. The data will need to be sent to the server and then to the other device.

Hi Erel, thank you for your reply.
Do you think it will be feasable, altough very difficult, to do something similar but within a regular GSM phone call?
The schema could be:
1. look up on a server for the crypto data needed
2. establish a regular phone call
3. intercept what is captured by your mic and send it in chunks to a crypto-function
4. trasmit the result of the crypto-function over the voice channel established at point 2

I understand the overhead of the crypto should be kept at a minimum and the conversation probably will not be as fluent as a regular one, but can it be done? Or simply there's no way to "read" the mic and then transmit those data (even unchanged) over the GSM call?

Umberto

I believe that the fundamental question is:

Can I, on my smartphone, get the digital data representing my voice during a phone call and change them before they are sent?

I do not know the answer and I think it is very difficult to obtain (using "regular" phone call!)

 

[Erel]

I don't think that it is possible.