He also points to recent victories such as the US government's decision to let the Patriot Act expire, and shifting opinion in the international community and technology sector. "The United Nations declared mass surveillance an unambiguous violation of human rights," he writes. "[And] beyond the frontiers of law, progress has come even more quickly." He points to the public's demand for 'basic technical safeguards such as encryption," which were once considered "esoteric and unnecessary" and are now "enabled by default."

We're still recording citizens' data "on a scale unprecedented in history."

Snowden also warns that the fight against mass surveillance is far from over. Governments around the world are still recording information like metadata — which can reveal as much about a person's interests and daily life as any direct surveillance — "on a scale unprecedented in history." He notes that political leaders such as the UK's prime minister David Cameron also continue to scare citizens by demanding new, more intrusive surveillance powers to combat terrorism. "For too long, we have been a passively tolerant society, saying to our citizens: As long as you obey the law, we will leave you alone," declared Cameron recently. Snowden may be hopeful that the "balance of power is beginning to shift," but he's right in saying there's work still to be done.