Weikeng Chen (UC Berkeley), Raluca Ada Popa (UC Berkeley)

File-sharing systems like Dropbox offer insufficient privacy because a compromised server can see the file contents in the clear. Although encryption can hide such contents from the servers, metadata leakage remains significant. The goal of our work is to develop a file-sharing system that hides metadata---including user identities and file access patterns.

Metal is the first file-sharing system that hides such metadata from malicious users and that has a latency of only a few seconds. The core of Metal consists of a new two-server multi-user oblivious RAM (ORAM) scheme, which is secure against malicious users, a metadata hiding access control protocol, and a capability sharing protocol.

Compared with the state-of-the-art malicious-user file-sharing scheme PIR-MCORAM (Maffei et al.'17), which does not hide user identities, Metal hides the user identities and is 500x faster (in terms of amortized latency) or 10^5x faster (in terms of worst-case latency).

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Yue Duan (Cornell University), Xuezixiang Li (UC Riverside), Jinghan Wang (UC Riverside), Heng Yin (UC Riverside)

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TKPERM: Cross-platform Permission Knowledge Transfer to Detect Overprivileged Third-party...

Faysal Hossain Shezan (University of Virginia), Kaiming Cheng (University of Virginia), Zhen Zhang (Johns Hopkins University), Yinzhi Cao (Johns Hopkins University), Yuan Tian (University of Virginia)

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Complex Security Policy? A Longitudinal Analysis of Deployed Content...

Sebastian Roth (CISPA Helmholtz Center for Information Security), Timothy Barron (Stony Brook University), Stefano Calzavara (Università Ca' Foscari Venezia), Nick Nikiforakis (Stony Brook University), Ben Stock (CISPA Helmholtz Center for Information Security)

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Bobtail: Improved Blockchain Security with Low-Variance Mining

George Bissias (University of Massachusetts Amherst), Brian N. Levine (University of Massachusetts Amherst)

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