At the height of the recent political unrest in Egypt, leaflets warned protesters not to use services like Facebook and Twitter to communicate, for fear of alerting the authorities about their intentions. Two security researchers have now created smart-phone apps that encrypt phone and text communications to offer a secure communication channel in such situations.

Two new applications for Android devices, called RedPhone and TextSecure, were released last week by Whisper Systems, a startup created by security researchers Moxie Marlinspike and Stuart Anderson. The apps are offered free of charge to users in Egypt, where protesters opposing ex-president Hosni Mubarak have clashed with police for weeks. The apps use end-to-end encryption and a private proxy server to obfuscate who is communicating with whom, and to secure the contents of messages or phone conversations. “We literally have been working night and day for the last two weeks to get an international server infrastructure set up,” says Anderson.

Anderson and Marlinspike are working with several nongovernmental organizations, such as MobileActive, to create a product that will be of use to other protesters. Of course, the software would not have helped when the Egyptian government took the unprecedented step of effectively shutting down both Internet and cellular communications across the entire country at the end of January.

RedPhone and TextSecure are primarily aimed at companies, especially those that want to relay sensitive data to workers on their cell phones. Attacks on phones are getting a lot easier, says Marlinspike. Whereas it used to cost $750,000 to mount an attack on a cellular network, researchers have already demonstrated methods using hardware that costs less than $20. “Right now, we are kind of at the point with cellular wireless where we were with [Wi-Fi] 10 years ago,” he says.

Some voice Internet systems, such as Skype, already use encryption, but the security of these systems is unproven, and it’s unclear to what degree the companies that offer them coöperate with authorities, says Marlinspike. “It is unclear what Skype’s encryption is and what they have done,” he says. “From limited analysis from a security research perspective, it doesn’t look good.”

The RedPhone software is open source, so anyone can audit the code, says Marlinspike. The two-way encryption is based on Zimmerman Realtime Transport Protocol, a proven way of exchanging cryptographic keys in order to establish a secure communication channel.

Working to offer the service to protesters in Egypt has suggested new features, says Anderson. For example, hiding the phone’s ability to receive encrypted communications might be necessary. In some countries, “just having an encrypted device or sending encrypted communications is in itself something that can get you in a lot of trouble,” Anderson says. “There is a need for a steganographic solution, where you can hide the fact that you are encrypting information in the first place.”