Nigeria, Aug. 8 -- The means of communication chosen to hatch a plot or stage a surprise is critical to the success of the plan.

For some whose names surfaced in the alleged coup investigation, communication was not limited to ordinary telephone calls. Messages were exchanged through WhatsApp, while some conversations were taken to Zangi, a lesser-known messaging application built to guarantee privacy and secure communication.

The distinction is important.

WhatsApp is one of the world's most widely used messaging platforms, familiar to virtually everyone with a smartphone.

Zangi is, however, different. Its appeal is centred more explicitly on private communication. The application has built much of its identity around private communic...