Bates, Adam, Kevin Butler, Micah Sherr, Clay Shields, Patrick Traynor, and Dan Wallach. “Accountable Wiretapping -or- I Know They Can Hear You Now.” In Network and Distributed System Security Symposium (NDSS), 2012.

In many democratic countries, CALEA wiretaps are used by law enforcement agencies to perform investigations and gather evidence for legal procedures. However, existing CALEA wiretap implementations are often engineered with the assumption that wiretap operators are trustworthy and wiretap targets do not attempt to evade the wiretap. Although it may be possible to construct more robust wiretap architectures by reengineering significant portions of the telecommunications infrastructure, such efforts are prohibitively costly. This paper instead proposes a lightweight \em accountable wiretapping system for enabling secure audits of existing CALEA wiretapping systems. Our proposed system maintains a tamper-evident encrypted log over wiretap events, enforces access controls over wiretap records, and enables privacy-preserving aggregate queries and compliance checks. We demonstrate using campus-wide telephone trace data from a large university that our approach provides efficient auditing functionalities while incurring only modest overhead. Based on publicly available wiretap reporting statistics, we conservatively estimate that our architecture can support tamper-evident logging for all of the United States’ ongoing CALEA wiretaps using three commodity PCs.

  author = {Bates, Adam and Butler, Kevin and Sherr, Micah and Shields, Clay and Traynor, Patrick and Wallach, Dan},
  booktitle = {Network and Distributed System Security Symposium (NDSS)},
  month = feb,
  title = {{Accountable Wiretapping -or- I Know They Can Hear You Now}},
  year = {2012}