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Jäger: Automated Telephone Call Traceback

David Adei, Varun Madathil, Sathvik Prasad, Bradley Reaves, Alessandra Scafuro

TL;DR

Jäger is introduced, a distributed secure call traceback system that can trace a call in a few seconds, even with partial deployment, while cryptographically preserving the privacy of call parties, carrier trade secrets like peers and call volume, and limiting the threat of bulk analysis.

Abstract

Unsolicited telephone calls that facilitate fraud or unlawful telemarketing continue to overwhelm network users and the regulators who prosecute them. The first step in prosecuting phone abuse is traceback -- identifying the call originator. This fundamental investigative task currently requires hours of manual effort per call. In this paper, we introduce Jäger, a distributed secure call traceback system. Jäger can trace a call in a few seconds, even with partial deployment, while cryptographically preserving the privacy of call parties, carrier trade secrets like peers and call volume, and limiting the threat of bulk analysis. We establish definitions and requirements of secure traceback, then develop a suite of protocols that meet these requirements using witness encryption, oblivious pseudorandom functions, and group signatures. We prove these protocols secure in the universal composibility framework. We then demonstrate that Jäger has low compute and bandwidth costs per call, and these costs scale linearly with call volume. Jäger provides an efficient, secure, privacy-preserving system to revolutionize telephone abuse investigation with minimal costs to operators.

Jäger: Automated Telephone Call Traceback

TL;DR

Jäger is introduced, a distributed secure call traceback system that can trace a call in a few seconds, even with partial deployment, while cryptographically preserving the privacy of call parties, carrier trade secrets like peers and call volume, and limiting the threat of bulk analysis.

Abstract

Unsolicited telephone calls that facilitate fraud or unlawful telemarketing continue to overwhelm network users and the regulators who prosecute them. The first step in prosecuting phone abuse is traceback -- identifying the call originator. This fundamental investigative task currently requires hours of manual effort per call. In this paper, we introduce Jäger, a distributed secure call traceback system. Jäger can trace a call in a few seconds, even with partial deployment, while cryptographically preserving the privacy of call parties, carrier trade secrets like peers and call volume, and limiting the threat of bulk analysis. We establish definitions and requirements of secure traceback, then develop a suite of protocols that meet these requirements using witness encryption, oblivious pseudorandom functions, and group signatures. We prove these protocols secure in the universal composibility framework. We then demonstrate that Jäger has low compute and bandwidth costs per call, and these costs scale linearly with call volume. Jäger provides an efficient, secure, privacy-preserving system to revolutionize telephone abuse investigation with minimal costs to operators.
Paper Structure (51 sections, 1 theorem, 2 equations, 10 figures, 3 tables)

This paper contains 51 sections, 1 theorem, 2 equations, 10 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Background
  3. Telephone Network Abuse
  4. Cryptographic Primitives
  5. Problem Statement
  6. Stakeholders and Adversaries
  7. Requirements
  8. Our Approach
  9. Jäger Overview
  10. Threat Model and Resiliency
  11. Frequently Asked Questions
  12. System and Protocol Design
  13. Jäger Architecture
  14. Protocol Overview
  15. Traceback Validation
  16. ...and 36 more sections

Key Result

Theorem 1

[Informal] Assuming the CPA security of the witness-encryption scheme, the unforgeability of the signature scheme, the security of the group signature scheme, the security of the OPRF protocol, and secure hash functions, Jäger achieves record confidentiality, the privacy of individual caller, blinds

Figures (10)

  • Figure 1: Jäger facilitates efficient and rapid traceback through collaborative efforts. Providers engage with the TA to secure membership, create labels, and acquire trace authorizations. Additionally, carriers send(receive) encrypted records to(from) the RS
  • Figure 2: During setup protocol, TA generates and announces public parameters. Providers request group membership and are assigned member secret key upon acceptance by the TA
  • Figure 3: In contribution protocol, provider submits ciphertexts, compliant with the protocol, to the Record Store
  • Figure 4: In the trace protocol, providers obtain labels, ciphertexts, and decryption authorization signatures for a call from TA. Here, the bold text shows $src\|dst\|j$ is not sent in plaintext but blinded as in OPRF
  • Figure 5: The Validate algorithm analyzes deviations from the ideal scenario to determine the call path and faulty sets
  • ...and 5 more figures

Theorems & Definitions (1)

  • Theorem 1