In the age of big data and the rise of the digital economy, no government agency plays a more central — or less understood — role than the mysterious National Security Agency. For years, the so-called Puzzle Palace was so secret that officials joked its acronym stood for “No Such Agency,” — until Edward Snowden published many of its biggest secrets online. Hear one of the NSA’s most senior officials explain the reality of what the NSA is — and what it isn’t.