Secure voice communication

When calling another person with your mobile phone, your communication can be monitored on multiple places. Governments all over the world have regulations which allows tapping of phone lines, this includes mobile phones. If you think your phone is tapped and your need a secure phone communication, it is worth looking into voice encryption.

There a vendors who offer mobile phones with voice encryption, but if you phone's hardware or firmware does not allow you to encrypt the normal voice calls, you can still use your data connection to send and receive encrypted voice data. The standard method for this is called the "SIP"-protocol. SIP is built-in in business Symbian-Phones and the N900 and available for Android Phones. SIP calls might be encrypted, but generally are not; this is a decision mostly of your SIP provider who has to support it.

Currently there are two convenient solutions for secure calling (one of them only on Android Phones). Both use the data connection of your (smart) phone, which means that you either need to be connected to a WiFi network or have a payable and reliable 3G connection ready.

Skype

Skype is a very well-known voice application. Skype uses encryption for the whole path of the voice communication.

Although the encryption seems to be resonably good¹ , Skype is not open about the technology they use for this. It's unknown if (some) governments have access to it or not. It seems to be safe for most countries and at least safer then using normal phone communication.

Because of the popularity of Skype and the fact mobile phone operators are loosing call-minutes, unfortunately some operators are blocking the use of Skype.

Depending on the phone you use, Skype might consume a lot of battery power. Keep this in mind when using Skype and are low on energy.

RedPhone

RedPhone is an application available only on the Android platform. It establishes a voice connection by a mediation through the RedPhone vendor's servers, so the are able to log every call you make with the RedPhone software.

RedPhone is very convenient to install on Android Phones. It's available from the Android Market. After installing it will use your normal phone contacts. It also has the ability to upgrade a phone call to an encrypted one while calling.

The main advantage of RedPhone over Skype is the way how it's integrated in your normal phone behaviour and the way it setups communication. It does not use a lot of battery power in standby. A big disadvantage is it's sound quality, which is not so very good, another big disadvantages that really limits its use is that the software is only available for android.
RedPhone needs a data-connection (WiFi or 3G) to operate.

Other methods

There are some other methods using VoIP encryption. Most of these application need a proper setup by a VOIP provider and are therefore not covered by this manual. Mostly VOIP connections are insecure if not explicitly stated otherwise.

Skype uses variable bit encoding which might leak information about the phrases spoken. See explanation and alternative encryption at http://zfoneproject.com/faq.html#vbr^{^}