This app promises privacy through encrypted messaging, but a US subpoena puts it to test

The company responsible for spreading top-of-the-line message encryption across the Internet has had a first legal skirmish with the US government. Open Whisper Systems — whose Signal app pioneered the end-to-end encryption technique now used by many messaging services — was subpoenaed for information about one of its users earlier in 2016. The American Civil Liberties Union, which represented the company, said the small San Francisco firm didn't produce the user's name, address, call logs or other details requested by the government. “That's not because Signal chose not to provide logs of information,” ACLU lawyer Brett Kaufman said in a telephone interview. “It's just that it couldn't.”

Created by anarchist yachtsman Moxie Marlinspike and a crew of surf-happy developers, Signal has evolved from a niche app used by dissidents and protest leaders into the foundation stone for the encryption of huge tranches of the world's communications data. When any of WhatsApp's billion-plus users sees a discreet lock icon with the words, “Messages you send to this chat and calls are now secured with end-to-end encryption,” they have Signal to thank. Facebook's recently launched private chat feature, Secret Conversations, uses Signal's technology; so does the incognito mode on Google's messenger service Allo.