Facebook wants to be a responsible steward of its users' private communications, according to Sullivan. "We need to make sure our systems are robust enough to have [governments] come in through the front door with the legal process, and not any other way," he said.
Facebook's security measures, which also include an advanced encryption technique called "perfect forward secrecy," are likely to evolve as governments and outside groups enhance their counter-measures.
"In an Internet context," Sullivan said, "security is in a constant state of improvement."
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