Whisper Systems was bought by Twitter in November 2011, and within half a year, both RedPhone and TextSecure, were released under the third version of the GNU General Public License. A year later, Marlinspike left Twitter to found Open Whisper Systems, which is funded by donations and grants, a neutrality that partially explains the high regard for its products. Since 2013, Open Whisper Systems has merged RedPhone and TextSecure into a single application, adding encrypted group chat and gradually developing Android and iOS versions with comparable feature sets. Recently, it released a beta version of Signal Desktop in the form of a Chrome app. So far, the desktop version, compared with the other versions, has a simplified feature set lacking password protection, for example. However, when linked to a mobile device, Signal Desktop provides centralized storage, as well as the increased usability of a mouse and a full-size keyboard. Signal is designed as a drop-in replacement for both for voice and text messaging apps (Figure 1).

Textsecure private messenger