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A Study of Bluetooth Access Control Based on NFT Soft Pairing

Zhiming Liang, Bin Chen, Ruijun Wu, Zhe Peng, Chen Sun, Shuo Wang

arXiv:2608.22754v1cs.CR

TL;DR

Conventional Bluetooth pairing can leave service authorization persistent and coarse-grained, while protocol-layer defenses face compatibility limitations. The paper introduces NFT soft pairing, combining native Bluetooth connectivity with blockchain-verified NFBT–NFDT authorization and challenge-response access checks. The prototype reports dynamic revocation, approximately 104ms verification latency, approximately 1.09s additional access latency, and 93.4% lower gas consumption for 15 batched credentials.

  • Problem

    Conventional Bluetooth pairing couples connectivity with persistent service authorization, while protocol-layer mitigations can have poor compatibility or limited attack coverage.

  • Method

    The framework uses three layers—Bluetooth, blockchain, and application—to govern access through bidirectional NFBT–NFDT bindings, challenge-response signatures, and on-chain state verification.

  • Results

    93.4% lower gas consumption is reported when minting 15 credentials in batch with ERC1155 compared with the conventional approach.

  • Takeaways & Limitations

    The design preserves native Bluetooth connectivity while making service authorization explicit, verifiable, time-limited, and revocable through NFT soft-pairing state.

Abstract

from arXiv · show

This paper proposes a Non-Fungible Token (NFT) soft pairing framework for Bluetooth service access control. Unlike conventional Bluetooth systems where pairing implicitly grants persistent service access, the proposed approach decouples native Bluetooth pairing from authorization without modifying the underlying protocol stack. The framework introduces a three-layer architecture consisting of a Bluetooth layer for connectivity, a blockchain layer for trusted execution and on-chain state verification, and an application layer where NFT soft pairing defines the authorization logic. In this design, Non-Fungible Bluetooth Tokens (NFBTs) represent user-side access credentials, while Non-Fungible Device Tokens (NFDTs) represent device identities. Their bidirectional on-chain binding forms a revocable and verifiable NFT soft pairing relationship. During access, users prove ownership of valid NFBTs through challenge-response signatures, and devices verify the corresponding on-chain state before granting service access. A prototype implemented with MetaMask and Ethereum demonstrates secure authentication, dynamic revocation, acceptable latency, and gas-efficient credential issuance based on ERC1155.

I. INTRODUCTION

The paper identifies persistent, coarse-grained Bluetooth authorization and protocol-layer compatibility limitations as security gaps. It proposes NFT soft pairing to separate native connectivity from dynamically verifiable service authorization.

  • Security gap: Conventional Bluetooth pairing can turn a compromised or mistakenly trusted relationship into persistent service access.Long-term Link Keys commonly preserve authorization until the user manually removes the pairing record.
  • Security gap: Static, coarse-grained pairing grants nearly unrestricted privileges until manual revocation, creating management difficulties in multi-device scenarios.
  • Existing approaches: Protocol-layer mitigations often have poor compatibility or address only specific attacks, making universal wireless protection challenging.
  • Existing approaches: Certificate-based application-layer authentication introduces centralized certificate-authority risk and complicates lifecycle management, auditing, and fine-grained control.
  • Proposed approach: NFT soft pairing decouples physical Bluetooth pairing from logical authorization through bidirectional NFBT–NFDT on-chain binding and a prototype supporting challenge-response verification and revocation.

II. SYSTEM MODEL

The system uses Bluetooth for compatible connectivity, blockchain for trusted authorization state, and an application-layer NFT relationship for access control. Users establish an NFBT–NFDT binding, then complete challenge-response and on-chain verification before access is granted and time-limited access is revoked.

  • Architecture: A three-layer architecture separates Bluetooth connectivity, blockchain authorization-state management, and application-layer NFT soft pairing.Native Bluetooth pairing remains a connectivity prerequisite rather than an authorization grant.
  • Architecture: NFBTs represent user credentials while NFDTs represent device identities in the authorization system.The application and blockchain layers connect these token roles through soft pairing.
  • Access workflow: Users establish an on-chain logical relationship between an NFBT and target NFDT before requesting Bluetooth service access.The relationship remains valid throughout the NFBT lifetime and avoids repeated pairing.
  • Access workflow: The device issues a 256-bit random challenge, receives a MetaMask signature and NFBT ID, recovers the signer address, and queries blockchain state.
  • Lifecycle control: After verification, the device records the authorized address and remaining duration, then terminates access and removes the address when authorization expires.

A. NFBT Contract

The NFBT contract issues, sells, verifies, and soft-pairs user access credentials. ERC1155 supports batch-oriented credential management, while verification requires matching device identity, soft pairing, ownership, and unexpired access.

  • Credential management: ERC1155 is adopted for NFBT and NFDT minting because batch minting and transfers reduce on-chain gas consumption and redundancy.
  • Credential management: The minting process creates NFBTs from device, duration, location, price, and quantity parameters after authorization checks.
  • Credential management: Purchasing NFBTs verifies payment, transfers tokens, and updates the buyer’s access expiration time through MetaMask-mediated blockchain transactions.
  • Soft pairing: Soft pairing establishes a unique bidirectional on-chain mapping between an NFBT and an NFDT.
  • Access verification: Access verification passes only when the token matches the device, is soft paired, is owned by the signer, and has not expired.

B. NFDT Contract

The NFDT contract initializes device identities and confirms their linkage to user access credentials. Cross-contract checks ensure that only registered, active devices are paired with corresponding NFBTs.

  • Device registration: Device registration binds a physical device identifier to an operator address on-chain and initializes active device metadata.
  • Pairing confirmation: Soft-pairing confirmation checks that the device is registered and active and that the NFBT corresponds to the device identifier.
  • Pairing confirmation: Cross-contract verification records the NFBT on the device side to preserve uniqueness and security of access authorization.

IV. SECURITY ANALYSIS

The framework places authentication after Bluetooth pairing but before service connection, using cryptographic signatures and on-chain NFBT ownership to block unauthorized access. It also addresses replay, centralization, and permission-lifecycle concerns through nonces, blockchain-based trust, and time-based revocation.

  • Authentication after pairing but before connection requires a valid MetaMask signature and verified ownership of an NFBT soft paired with the target device.This prevents Bluetooth pairing compromise alone from granting service access.
  • A dynamically generated random nonce prevents intercepted historical signatures from being reused in later authentication processes.The challenge–response design therefore mitigates replay attacks.
  • Blockchain-based trust removes the inherent limitations of centralized architectures.The blockchain serves as the trust anchor for authorization verification.
  • NFBT metadata supports time-based access control, with expired soft-pairing relationships and associated privileges atomically revoked from on-chain state.This provides fine-grained lifecycle management.

A. Experimental Procedure

The experimental procedure uses a MetaMask-connected client to display owned NFBTs and their validity, then performs challenge signing and Bluetooth authorization. The procedure concludes with a successful connection page showing authorization information such as remaining connection time.

  • The NFBT Client runs on a local Ethereum test network and uses Vue.js, Web3.js, and MetaMask for blockchain interaction.The contracts were deployed through Remix on Ganache with Ethereum London hard fork rules enabled.
  • The user logs into the NFBT Client through MetaMask before opening the Bluetooth wallet interface.Figure 4(a) depicts login, while Figure 4(b) presents the user information page.
  • The wallet lists owned NFBTs and their statuses, distinguishing expired token ID 2 from valid token ID 1.Token ID 1 can be used to establish a connection with Device1, whereas token ID 2 is invalid for access verification.
  • After selecting valid NFBT ID 1, the user signs a challenge value through MetaMask before access verification completes.Figure 4(c) shows challenge signing during the interaction among the user device, Bluetooth service device, and blockchain network.
  • Successful verification produces a connection success page displaying authorization information, including remaining available connection time.Figure 4(d) shows the Bluetooth service device returning the verification result to the user.

B. Performance Analysis

The framework evaluates authentication latency, revocation, and Ethereum gas costs. Results show dynamic revocation, low verification latency, and substantially lower batch-minting costs with ERC1155, alongside added signing delay.

  • Authentication latency: Authentication delay is defined as the sum of challenge generation, user signing, and device verification time.Verification includes address recovery, on-chain NFBT state querying, and permission checking.
  • Authentication latency: Approximately 104ms of verification latency remains low and relatively stable because blockchain state checks use read-only view calls.The verification phase does not require state modification or block confirmation.
  • Authentication latency: Approximately 1.09s of additional latency is introduced versus unauthenticated conventional Bluetooth connections, primarily through user-side signing.The signing overhead is attributed to MetaMask confirmation and signature-generation computation.
  • Revocation and security: A 1s polling interval enables automatic connection termination when an NFBT expires, providing dynamic permission revocation without manual intervention.The Bluetooth service device periodically checks authorization status for devices in the control set.
  • Revocation and security: The scheme provides decentralized strong identity authentication and can prevent unauthorized malicious connections even when pairing is compromised.It also supports fine-grained permission revocation, with a marginal reduction in initial connection efficiency.
  • Gas consumption: RegisterDevice has the highest gas cost because it persistently stores token metadata and device-association state on chain.Gas consumption varies by function and is not directly comparable across application operations.
  • Gas consumption: 93.4% lower gas consumption is achieved when minting 15 credentials in batch with ERC1155 compared with the conventional approach.ERC721 rises from 152,960 to 2,055,000 gas, while ERC1155 remains at 134,625 gas for same-ID credential minting.

VI. CONCLUSION

The proposed NFT soft pairing framework separates Bluetooth connectivity from service authorization through a three-layer architecture. Its prototype demonstrates secure authentication, efficient revocation, and acceptable performance overhead while preserving existing Bluetooth compatibility.

  • VI. CONCLUSION: The three-layer architecture preserves native Bluetooth connectivity while blockchain verification and application-layer NFT soft pairing govern authorization.NFBTs and NFDTs form a bidirectional relationship whose on-chain state explicitly controls access.
  • VI. CONCLUSION: The prototype demonstrates dynamic, revocable, and fine-grained access control with acceptable performance overhead.The design retains compatibility with existing Bluetooth infrastructure and uses cryptographic verification.
  • VI. CONCLUSION: NFT soft pairing provides a general abstraction that separates Bluetooth connectivity from trust.Access is governed by on-chain NFT state rather than pairing status alone.
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