Differential privacy is cool. However, I looked at Google's RAPPOR algorithm (deployed in Chrome, and clearly designed with real-world considerations in mind) in some depth, and I found that RAPPOR needs millions to billions of measurements to become useful, even while exposing users to potentially serious security risks (epsilon = ln(3), so "bad things become at most 3x more likely"). Much better than doing nothing, but we'll continue to need non-cryptographic solutions (NDA's etc.) for many cases.
Differential privacy is cool. However, I looked at Google's RAPPOR algorithm (deployed in Chrome, and clearly designed with real-world considerations in mind) in some depth, and I found that RAPPOR needs millions to billions of measurements to become useful, even while exposing users to potentially serious security risks (epsilon = ln(3), so "bad things become at most 3x more likely"). Much better than doing nothing, but we'll continue to need non-cryptographic solutions (NDA's etc.) for many cases.