Are any encrypted messaging apps fail-safe? Subjects of Mueller’s investigation are about to find out.

"Encryption is the best tool people have for defending against hackers, cybercriminals and government surveillance, said Riana Pfefferkorn, a cryptography fellow at the Stanford Center for Internet and Society. Still, “your communications encryption choices are only worth as much as the trustworthiness of the people you're talking to,” she said.

“If someone in a group chat is a police informant, or your friend shows the messages you sent them to someone you didn't want to see them, then encrypting messages in transit and encrypting your own phone doesn't do you any good,” Pfefferkorn noted. “This has always been a privacy risk, though, well before the advent of encrypted apps and devices. If your trust turns out to have been misplaced, that's the risk you take.”"