Karim Eldefrawy

Cryptography, Cybersecurity, Privacy

Co-founder and CTO at Confidencial.io
2017-2021: SRI
2011-2016: HRL Laboratories
2006-2010: PhD@UC Irvine

Scientific curiosity

Scientific knowledge map · Paper #13

Group Distance Bounding Protocols (Short Paper)

Srdjan Čapkun, Karim Eldefrawy, and Gene Tsudik

2011 · 4th International Conference on Trust and Trustworthy Computing (TRUST)

  • Theory
  • protocol
  • primitive

What does the paper try to establish?

How can several provers and verifiers establish one-way distance bounds more efficiently than running every verifier-prover pair separately, while retaining a meaningful security argument?

What is the proposed answer?

A passive verifier can infer a distance bound by observing an active distance-bounding exchange and combining time-difference-of-arrival geometry with the active verifier's bound. Rotating a subset of verifiers through the active role reduces message cost, but the guarantees depend on trusted active verifiers, known locations, radio and timing assumptions, and the security of the underlying pairwise protocol.

Abstract

Distance bounding (DB) protocols allow one entity, the verifier, to securely obtain an upper-bound on the distance to another entity, the prover. Thus far, DB was considered mostly in the context of a single prover and a single verifier. There has been no substantial prior work on secure DB in group settings, where a set of provers interact with a set of verifiers. The need for group distance bounding (GDB) is motivated by many practical scenarios, including: group device pairing, location-based access control and secure distributed localization. This paper addresses, for the first time, one-way GDB protocols by utilizing a new passive DB primitive. We show how passive DB can be used to construct secure and efficient GDB protocols for various one-way GDB settings. We analyze the security and performance of proposed protocols and compare them with existing DB techniques extended to group settings.

Provenance: Transcribed from the checked-in short-paper PDF; only typography, discretionary hyphenation, and line-break artifacts were normalized.

Six dimensions, kept separate

The chart summarizes documented evidence and process. It is not a correctness probability, confidence score, or ranking, and no composite score is calculated.

The visual spider chart requires JavaScript. The complete values and rationales follow in text.

LowMediumHighN/A = not assessed

A smaller value means less documented support for that dimension, not that the paper is false or unimportant.

Epistemic evidence Medium

The paper defines the primitive and group settings, gives a geometric security argument, and quantifies message savings. The security treatment is conditional and analytical, and no implementation, simulation, or machine-checked proof is supplied.

Passive distance-bounding primitive and geometric argument Message-count analysis and active-verifier tradeoff Security analysis and malicious-active-verifier boundary Conclusions and future work
Auditability High

A complete author copy is checked into the site with source route, page count, and SHA-256 identity. Definitions, protocol steps, and analytical arguments are directly inspectable, though there is no executable artifact.

GDB cases, environmental assumptions, and adversary One-way group protocol construction Security analysis and malicious-active-verifier boundary
Production provenance Medium

Named authorship, an archived author copy, and a DOI establish baseline provenance. Contributor roles, revision history, analysis scripts, and tool use are not documented.

Motivation, contribution, and one-way GDB scope Official short-paper publication record
External scrutiny Medium

Publication as a TRUST short paper indicates venue review, but review reports, corrections, independent formal analysis, and empirical replication were not located.

Official short-paper publication record
Reception High

ResearchGate displayed 14 citations on 2026-07-11, which meets the rubric's 11-or-more high band. The count is index-specific and may merge related versions.

Citation-count snapshot
Contribution significance Medium

The paper introduces a clear group generalization and a reusable passive primitive, but the short version leaves important trust, synchronization, and implementation questions open.

Motivation, contribution, and one-way GDB scope Passive distance-bounding primitive and geometric argument Conclusions and future work

Assessment: Ai draft author review pending · 2026-07-11 · rubric 0.2. These dimensions describe documented support and process, not truth, correctness, or a universal ranking. No composite score is calculated.

Hierarchical knowledge map

Collapse a branch for a top-level reading, or follow its source links and child nodes to audit the evidence and boundaries underneath it.

paper

One-way group distance bounding

A short paper defining group distance-bounding settings and introducing passive observation as a primitive for cheaper multi-party protocols.

Motivation, contribution, and one-way GDB scope
  1. scope One-way group settings explicitly scoped

    The construction addresses many-prover/many-verifier, one-prover/many-verifier, and many-prover/one-verifier one-way cases; mutual GDB is acknowledged but left outside this short paper.

    GDB cases, environmental assumptions, and adversary Conclusions and future work
  2. primitive Passive distance bounding proposed

    A passive verifier timestamps the active verifier's commitment/challenge and the prover's response, then combines a time-difference-of-arrival hyperbola with the active distance bound to derive its own upper bound.

    Passive distance-bounding primitive and geometric argument
    1. security argument

      Why a prover cannot shorten only the passive bound

      conditional argument

      Under the timing geometry, making the passive verifier infer an impossibly short distance would also require defeating the active verifier's underlying distance-bound exchange.

      Passive distance-bounding primitive and geometric argument
  3. protocol

    Active/passive GDB protocol

    proposed

    A selected fraction of verifiers runs active pairwise exchanges while remaining verifiers observe them, permitting each active exchange to contribute bounds to more than one verifier.

    One-way group protocol construction
  4. analytic evidence

    Communication-cost analysis

    calculated

    For the paper's 30-prover/30-verifier example, an 80% active fraction saves about one third of messages and a 60% active fraction saves more than half relative to naive pairwise execution.

    Message-count analysis and active-verifier tradeoff
  5. analytic evidence

    Security analysis

    conditional analysis

    The paper relates success probability to the underlying distance-bounding protocol and the chance that an adversary controls active verifiers; it provides analytical metrics rather than a reduction-style theorem or machine-checked proof.

    Security analysis and malicious-active-verifier boundary
  6. limitation

    Malicious active verifier boundary

    material

    An active verifier can lie about location or send challenges early, so passive conclusions are only as trustworthy as the active participant and underlying protocol; multiple simultaneous verifiers may be needed for secure localization.

    Security analysis and malicious-active-verifier boundary
  7. limitation group

    Unresolved scope

    explicitly reported

    The short paper has no implementation or noisy-channel evaluation and leaves mutual GDB, passive operation without known verifier locations, denial of service, and realistic group-radio conditions to future work.

    Conclusions and future work

Source index

Locators state the depth of the current audit. PDF page numbers, where present, are one-based file pages; metadata-, summary-, and abstract-bounded records explicitly identify their limitations.

  1. Motivation, contribution, and one-way GDB scope Abstract and Section 1, PDF pages 1-2
  2. GDB cases, environmental assumptions, and adversary Section 2, PDF pages 2-3
  3. Passive distance-bounding primitive and geometric argument Section 3, PDF pages 4-5
  4. One-way group protocol construction Section 4, PDF pages 5-6
  5. Message-count analysis and active-verifier tradeoff Section 5.1, PDF page 6
  6. Security analysis and malicious-active-verifier boundary Section 5.2, PDF pages 6-7
  7. Conclusions and future work Section 7, PDF page 8
  8. Official short-paper publication record TRUST 2011, DOI record
  9. Citation-count snapshot ResearchGate displayed Citations (14), observed 2026-07-11; the page may merge or separate versions differently from other indexes.