Ionosphere is a bot for bouncing Signal messages to groups of users to facilitate messaging that protects the social graph.
Many activists, journalists and others depend on group messages in order to communicate and spread information, however in repressive contexts, this is often not desirable to expose the list of people on a list to each member of the group, as it may put the members of it at risk. Ionosphere mitigates that risk by building on the Hubot bot platform, and the Signal secure communication application to create a bot that send messages to a group of people while preserving their privacy by ensuring that the list of phone numbers is not visible to all members of the group.
Though Signal is one of the most popular tools for secure communication, it has certain shortcomings for large-scale organizing. Namely, it exposes the phone number of every member of a group to every other member of that group. Ionosphere provides an intermediary that allows for distributing messages to a group without exposing those phone numbers, thus helping to protect activists using Signal.