Moxie Marlinspike has ... created an encryption program that scrambles messages until they reach the intended reader. The software is effective enough to alarm governments. British Prime Minister David Cameron called protected-messaging apps a safe space" for terrorists. The following week, President Barack Obama called them "a problem." In a research paper released Tuesday, 15 prominent technologists cited three programs relying on Mr. Marlinspike's code as options for shielding communications. His encrypted texting and calling app, Signal, has come up in White House meetings. Former National Security Agency contractor Edward Snowden, who leaked troves of U.S. spying secrets, urged listeners to use "anything" that Mr. Marlinspike releases. That endorsement was "a little bit terrifying," Mr. Marlinspike says. But he says he sees an opening, following Mr. Snowden's revelations, to demystify, and simplify, encryption, so more people use it. Consumer encryption tools ... have been around since the early 1990s, but most are so cumbersome that few people use them, [limiting] the use of encryption to a level law enforcement has mostly learned to live with. Adding easy-to-use encryption that companies can't unscramble to products used by millions changes that calculus. Technology companies, once cozy with Washington, sound increasingly like Mr. Marlinspike. Apple, Facebook, Google and others are resisting efforts to give the government access to encrypted communications.