DARPA wants to make a better, more secure, version of WhatsApp April 15, 2019 https://www.trustedreviews.com/news/darpa-wants-make-better-secure-version-whatsapp-3696558
If it were distributed (in IPv6 peer-to-peer Internet or even decentralized e-mail sense), it would be really interesting.
I wouldn't trust them blindly. If it would be just specs about protocol and open-source reference implementation then protocol can be audited by community. There could be developed alternative implementations. Or just some chosen findings and features from specs could be used by other open-source projects.