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From Scores to Queues: Operationalizing Cross-Chain Obfuscation Signals for Smart-Contract Audits

Yao Zhao, Zhang Sheng, Shengchen Duan, Shen Wang

TL;DR

This work tackles obfuscation in cross-chain smart-contract auditing by introducing HObfNET, a fast hierarchical attention model that surrogate-scores the Ethereum-based Obfs_Tool on BSC, Polygon, and Avalanche. It demonstrates that Ethereum cutoffs do not transfer cleanly across chains, establishing chain-specific main (p99) and emergency (p99.9) thresholds and detailing the operational impact of drift. The authors characterize the high-obfuscation tail as defined by rare selectors, external-call enrichment, and low signature density, and show that tail templates diffuse between chains with a bias from smaller to larger ecosystems, validating cross-chain coordination. Public incident alignment indicates real-world utility, with cross-chain spillovers present in high-score queues, supporting a practical two-tier audit workflow and cross-chain linkage for security operations.

Abstract

Obfuscation substantially increases the interpretation cost of smart-contract auditing, while the comparability and transferability of obfuscation signals across chains remain unclear. We present HObfNET as an efficient surrogate of Obfs_Tool (ObfProbe), enabling fast cross-chain scoring at scale. The model aligns well with tool outputs on Ethereum (PCC 0.9158, MAPE 8.20 percent) and achieves 8-9 ms per contract, a 2.3k-5.2k times speedup over second-level Obfs_Tool runs, enabling million-scale scoring. On large BSC, Polygon, and Avalanche corpora, we find systematic score drift: fixed-threshold transfer inflates and deflates candidate queues, motivating within-chain main and extreme thresholds (p99 and p99.9) and an actionable queueing strategy. The high-score tail exhibits rare selectors, external-call opcode enrichment, and low signature density; a proxy indicator is enriched in the BSC high-score queue, enabling secondary triage. Cross-chain reuse analysis shows tail enrichment and directional diffusion, with traceable same-hash cases across chains. In publicly alignable incident samples, all fall into the p99 queue; Transit Swap DEX Hack and New Free DAO Flash Loan exhibit cross-chain spillover, indicating real-world hit and prioritization value. We deliver a two-tier audit queue and cross-chain linkage workflow to support practical multi-chain security operations.

From Scores to Queues: Operationalizing Cross-Chain Obfuscation Signals for Smart-Contract Audits

TL;DR

This work tackles obfuscation in cross-chain smart-contract auditing by introducing HObfNET, a fast hierarchical attention model that surrogate-scores the Ethereum-based Obfs_Tool on BSC, Polygon, and Avalanche. It demonstrates that Ethereum cutoffs do not transfer cleanly across chains, establishing chain-specific main (p99) and emergency (p99.9) thresholds and detailing the operational impact of drift. The authors characterize the high-obfuscation tail as defined by rare selectors, external-call enrichment, and low signature density, and show that tail templates diffuse between chains with a bias from smaller to larger ecosystems, validating cross-chain coordination. Public incident alignment indicates real-world utility, with cross-chain spillovers present in high-score queues, supporting a practical two-tier audit workflow and cross-chain linkage for security operations.

Abstract

Obfuscation substantially increases the interpretation cost of smart-contract auditing, while the comparability and transferability of obfuscation signals across chains remain unclear. We present HObfNET as an efficient surrogate of Obfs_Tool (ObfProbe), enabling fast cross-chain scoring at scale. The model aligns well with tool outputs on Ethereum (PCC 0.9158, MAPE 8.20 percent) and achieves 8-9 ms per contract, a 2.3k-5.2k times speedup over second-level Obfs_Tool runs, enabling million-scale scoring. On large BSC, Polygon, and Avalanche corpora, we find systematic score drift: fixed-threshold transfer inflates and deflates candidate queues, motivating within-chain main and extreme thresholds (p99 and p99.9) and an actionable queueing strategy. The high-score tail exhibits rare selectors, external-call opcode enrichment, and low signature density; a proxy indicator is enriched in the BSC high-score queue, enabling secondary triage. Cross-chain reuse analysis shows tail enrichment and directional diffusion, with traceable same-hash cases across chains. In publicly alignable incident samples, all fall into the p99 queue; Transit Swap DEX Hack and New Free DAO Flash Loan exhibit cross-chain spillover, indicating real-world hit and prioritization value. We deliver a two-tier audit queue and cross-chain linkage workflow to support practical multi-chain security operations.
Paper Structure (45 sections, 8 equations, 2 figures, 9 tables)

This paper contains 45 sections, 8 equations, 2 figures, 9 tables.

Table of Contents

  1. Introduction
  2. Related Work
  3. Model Construction and Evaluation
  4. Task Definition
  5. Training Data and Preprocessing
  6. Supervision Signals
  7. Model Architecture
  8. Overview
  9. Local Encoder (local patterns)
  10. Global Encoder (long-range dependencies)
  11. Masked Mean Pooling (padding control)
  12. Multi-task Enhancement (noise control and interpretability)
  13. Training Objective and Optimization
  14. Experimental Setup
  15. Evaluation Metrics
  16. ...and 30 more sections

Figures (2)

  • Figure 1: The overall architecture of HObfNET: data processing, local encoder, global encoder, and a multi-task output layer that reconstructs domain features.
  • Figure 2: Cross-chain reuse overlap summaries.