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Showing posts from July, 2014

Secure voice communication on Android

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While the topic of secure voice communication on mobile is hardly new, it has been getting a lot of media attention following the the official release of the Blackphone, Consequently, this is a good time to go back to basics and look into how secure voice communication is typically implemented. While this post focuses on Android, most of the discussion applies to other platforms too, with only the mobile clients presented being Android specific.
Voice over IP Modern mobile networks already encrypt phone calls, so voice communication is secure by default, right? As it turns out, the original GSM encryption protocol (A5/1) is quite weak and can be attacked with readily available hardware and software. The somewhat more modern alternative (A5/3) is also not without flaws, and in addition its adoption has been fairly slow, especially in some parts of the world. Finally, mobile networks depend on a shared key, which while protected by hardware (UICC/SIM card) on mobile phones, can be obtai…