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Assume that I don't have any Internet access in my country. The only thing that I have is a mobile phone with a 3G or 4G SIM card inside. The mobile operator didn't provide any Internet access also.

Now I want to send some data (Text/Voice) to my friend in another country. Is there any way? How I can do it?

And if I want the communication to be secure, what shall I do? I mean I don't want to anybody be able gain the data, except my friend. is there any way? If so, how?

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Yes, you could encrypt your data.

This will be hard if you don't have a smartphone. You could manually encrypt your text messages using One-time pad (Cold War tactics basically). Manually encrypting voice messages is not possible, unless you invent some kind of secret language (which will never be a 100% secure).

If you do have android, have a look here: https://www.eff.org/secure-messaging-scorecard Some of these apps (Like Open WhisperSystems TextSecure) can use regular SMS.

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