Bridgefy

Bridgefy is a Mexican software company with offices in Mexico and California, USA, dedicated to developing mesh-networking technology for mobile apps. It was founded circa 2014 by Jorge Rios, after conceiving the idea while participating in a tech competition called StartupBus. Bridgefy's smartphone ad hoc network technology, apparently using Bluetooth Mesh, is licensed to other apps. The app gained popularity during protests in different countries since it can operate without Internet, using Bluetooth instead. Aware of the security issues of not using cryptography and the criticism surrounding it, Bridgefy announced in late October 2020 that they adopted the Signal protocol, in both their app and SDK, to keep information private.
Usage.
The app gained popularity as a communication tactic during the 2019–2020 Hong Kong protests and Citizenship Amendment Act protests in India, because it requires people who want to intercept the message to be physically close because of Bluetooth's limited range, and the ability to daisy-chain devices to send messages further than Bluetooth's range.
Security.
In August 2020, researchers published a paper describing numerous attacks against the application, which allow de-anonymizing users, building social graphs of users’ interactions (both in real time and after the fact), decrypting and reading direct messages, impersonating users to anyone else on the network, completely shutting down the network, performing active man-in-the-middle attacks to read messages and even modify them.
In response to the disclosures, developers acknowledged that "no part of the Bridgefy app is encrypted now" and gave a vague promise to release a new version "encrypted with top security protocols". Later developers said they plan to switch to Signal protocol, which is widely recognized by cryptographers and used by Signal and WhatsApp, achieving it in both the Bridgefy App and SDK by late October 2020. Several of the improvements include end-to-end encryption; and the impossibility of a third person impersonating any other user, man-in-the-middle attacks done by modifying stored keys, and historical proximity tracking; among others.