Security, privacy and abuse prevention

A complex challenge when using encryption to enforce access control on resources stored at external cloud providers is the efficient enforcement of access revocation to users who know the key used for encrypting the outsourced resources. We present an approach addressing this challenge that relies on a mixing phase. The mixing phase transforms a plaintext resource into an encrypted resource...

The seamless integration of technology into the lives of youth has raised concerns about their digital safety. While prior work has explored youth experiences with physical, sexual, and emotional threats—such as bullying and trafficking—a comprehensive and in-depth understanding of the myriad threats that youth experience is needed. By synthesizing the perspectives of 36 youth and 65 adult...

We train language models (LMs) with federated learning (FL) and differential privacy (DP) in the Google Keyboard (Gboard). We apply the DP-Follow-the-Regularized-Leader (DP-FTRL)~\citep{kairouz21b} algorithm to achieve meaningfully formal DP guarantees without requiring uniform sampling of client devices. To provide favorable privacy-utility trade-offs, we introduce a new client participation...

The problem of learning threshold functions is a fundamental one in machine learning. Classical learning theory implies sample complexity of $O(\xi^{-1} \log(1/\beta))$ (for generalization error $\xi$ with confidence $1-\beta$). The private version of the problem, however, is more challenging and in particular, the sample complexity must depend on the size $|X|$ of the domain. Progress on...