Strong encryption methods have been in circulation since at least July 1919, the U.S. patent date for the Vernam Cipher -- what we now know as exclusive OR operations on a one time pad. Provided sender and receiver follow the protocol and use the technique correctly, messages encoded by strong encryption methods are difficult to decipher by any other than the intended recipient.
The amount of usage of strong encryption over the decades is by its nature unknowable. The United States government has discouraged its use, but in the face of emerging realities has slowly opened up the use of longer keys and increasingly sophisticated encryption techniques. Firms and agencies in other nations have not been so constrained.
A bit of history -- U.S. Patent 6,757,699 was developed by Douglas Lowry (then Professor of Business and Marketing) and financed by his employer, Franciscan University of Steubenville, Ohio. On November 19, 2004 Lowry, David Skiviat, and Adam Scurti, Esq. of Franciscan University met in Fort Meade, MD with representatives of the National Security Agency and the National Institutes of Standards and Technology. The NSA and NIST attendees encouraged us to put our product out in the marketplace; they expressed confidence that, with thirty percent of the world's computing resources at their disposal, NSA could break anything that our technology would throw at them.
We did not share their optimism. We did not want our technology to fall into the wrong hands, to our nation's sorrow. We put the Pryvit technology back on the shelf, unused.
Times change. Emergence in the marketplace of "end-to-end" encryption and the proliferation of successful cyber attacks against the United States has prompted FBI Director James Comey (WSJ July 6, 2015) to invite a "robust debate" about the use of strong encryption. These calls continue unabated, as for example, Time for a Rigorous National Debate About Surveillance, Mike Pompeo and David Rivkin Jr. (WSJ January 4, 2016).
Problem 1: Balance between citizens' needs for privacy and the nation's needs for terrorist surveillance;
Problem 2: Defense against cyber attack by foreign state-sponsored intruders
Problem 3: Secure transmission of computer data