Silentel is a free Android application developed by Ardaco a.s. that provides secure communication for closed groups. It is designed to protect voice and data communication against wiretapping and interception. Silentel offers secure voice calls between two participants, secure conference calls between two or more users, secure messaging, and secure file transfer.

One of the standout features of Silentel is its use of separate contacts that are not stored on the phone after logging off the application. This ensures that all communication is kept secure and private. During voice calls, all information transmitted by the Silentel system is encrypted by the sender and decrypted only by the receiver. The same level of security is applied to conference calls and messaging.

Another great feature of Silentel is the ability to send encrypted documents, images, or any other files. The application offers the option to take a picture or video using the camera, record audio, and send it as a file to any recipient in an easy and simple way.

Overall, Silentel is a reliable and easy to use application that offers the highest level of security for closed group communication. It is perfect for individuals or businesses that want to protect sensitive information from eavesdropping and interception.