Design and Implementation of a Digital Forensics Evidence Management System

Design and Implementation of a Digital Forensics Evidence Management System
Abstract
Digital evidence has become indispensable in modern criminal investigations, yet its management from collection to courtroom presentation faces persistent challenges including tampering risks, broken chain of custody, and inefficient cross-jurisdictional collaboration. Current blockchain-based digital evidence management systems focus primarily on technical implementation while failing to adequately reflect the procedural legitimacy requirements of criminal justice practice, and lack systematic support for role and authority management in multi-party cooperation scenarios. This project presents the design and implementation of a Blockchain-based Digital Evidence Management System (B-DEMS) that addresses these limitations by systematically integrating forensic procedures with multi-party authorization. The system implements the complete evidence lifecycle from registration to disposal, providing differentiated approaches for inter-agency sharing and conditional access control. B-DEMS distinguishes between voluntary submission and compulsory seizure through multi-signature authentication and smart contract-based conditional decryption. The system employs a sender-receiver architecture with encrypted evidence transfer to support secure cross-jurisdictional sharing while protecting data in transit. Transaction-based destruction protocols ensure transparency and auditability in evidence disposal. Validation through scenario-based case studies and performance evaluation demonstrates that B-DEMS achieves practical applicability for law enforcement agencies while maintaining the procedural legitimacy necessary for court acceptance.
Keywords: Digital Forensics; Evidence Management; Blockchain; Chain of Custody; Smart Contracts; Procedural Legitimacy
Chapter 1: Introduction
1.1 Research Background
Digital evidence plays an increasingly critical role in contemporary criminal investigations. Data from mobile devices, surveillance systems, and digital communications can determine case outcomes in fraud, cybercrime, narcotics trafficking, and violent crime investigations. Global losses from cybercrime are projected to reach $10.5 trillion by 2025, and cross-border complexity coupled with inconsistent regulations further complicates the work of law enforcement agencies.
The integrity of digital evidence is a prerequisite for its admissibility in court. Chain of Custody (CoC) processes ensure that digital evidence is meticulously managed and documented from its point of origin through its use in court. However, traditional paper-based CoC processes suffer from high risk of human error and procedural defects, while centralized databases face internal threats and unauthorized modification risks. When evidence moves across jurisdictions—from police collection to forensic analysis to courtroom presentation—the absence of cryptographically verifiable audit trails makes evidence tampering possible and raises questions about its legitimacy.
Blockchain technology, with its characteristics of decentralization, immutability, and transparent traceability, offers a new paradigm for digital evidence management. B-DEMS (Blockchain-based Digital Evidence Management System) addresses the disconnect between existing blockchain systems and actual criminal justice procedures by systematically reflecting real investigative practices .
1.2 Problem Statement
Current digital evidence management systems face several critical challenges:
Disconnect Between Procedural Legitimacy and Technical Implementation: Existing blockchain-based systems focus primarily on technical aspects such as integrity verification and storage, failing to adequately reflect the complex procedural requirements of criminal justice practice. Judicial authorities require evidence to meet procedural, legal, and ethical standards, which purely technical solutions cannot satisfy .
Inadequate Authority Management in Multi-Party Cooperation: International cooperative investigations require systematic approaches to participant roles and authorities, yet existing systems inadequately address multi-party cooperation processes .
Absence of Complete Lifecycle Management: Existing systems focus primarily on collection and storage phases, lacking systematic management of the complete evidence lifecycle from registration to disposal, particularly in the destruction phase where transparency and auditability are essential .
Cross-Jurisdictional Collaboration Barriers: Differences in legal frameworks across jurisdictions complicate cross-border evidence sharing, with no standardized technical solution to support compliant evidence exchange .
1.3 Research Objectives
This project aims to design and implement a Blockchain-based Digital Evidence Management System (B-DEMS) with the following objectives:
1. Systematically reflect actual criminal justice procedures, achieving procedural legitimacy across jurisdictions by distinguishing between voluntary submission and compulsory seizure .
2. Implement complete evidence lifecycle management from registration to disposal, including transaction-based destruction protocols that ensure transparency and auditability .
3. Support secure evidence sharing between investigative entities through sender-receiver architecture with encrypted transfer and smart contract-based conditional decryption .
4. Implement multi-signature authentication and role-based access control for differential access rights according to evidence acquisition methods .
5. Achieve practical performance levels that enable adoption by law enforcement agencies with varying technical capabilities .
1.4 Thesis Structure
This thesis comprises five chapters. Chapter 1 introduces research background and objectives; Chapter 2 reviews related work in digital forensics standards and blockchain-based evidence management; Chapter 3 presents the system architecture and design; Chapter 4 describes implementation details and evaluation results; Chapter 5 concludes and discusses future work.
Chapter 2: Literature Review
2.1 Digital Forensics Standards and Best Practices
NIST SP 800-86 provides the foundational framework for integrating forensic techniques into incident response. The standard defines four phases: Collection (data identification, labeling, recording, and acquisition using procedures that preserve integrity), Examination (assessment and extraction of data of interest using automated and manual methods), Analysis (deriving useful information using well-documented methods), and Reporting (describing actions employed, explaining tool and procedure selection, and providing recommendations) . This process model, while IT-focused rather than law-enforcement-focused, establishes the conceptual foundation for systematic forensic handling .
ISO/IEC 27037:2012 provides guidelines for specific activities in handling digital evidence: identification, collection, acquisition, and preservation of potential digital evidence that may be of evidential value. The standard provides guidance to individuals regarding common situations encountered throughout the digital evidence handling process and assists organizations in their disciplinary procedures and in facilitating the exchange of potential digital evidence between jurisdictions . This international standard is particularly relevant for cross-border investigations where evidence must satisfy multiple legal frameworks.
ISO/IEC 27037:2012 (R2024) covers digital storage media used in standard computers, mobile phones, PDAs, memory cards, mobile navigation systems, digital still and video cameras (including CCTV), and networks based on TCP/IP and other digital protocols . The standard's broad applicability makes it the reference framework for digital evidence handling across device types and jurisdictions.
PD CEN/TS 18053-1:2024 provides overview and concepts for Digital Chain of Custody (dCoC) for CBRNE evidence. It introduces the concept of Custody Transfer Point (CTP) within the dCoC process, including identification and audit of custody ownership and metadata governance to ensure data integrity at each CTP . This standard complements ISO/IEC 27037 by providing detailed guidance on custody transfer mechanics.
2.2 Blockchain-Based Digital Evidence Management
B-DEMS (Blockchain-based Digital Evidence Management System) represents a comprehensive approach that addresses the gap between technical integrity and investigative procedures. The system encompasses the entire evidence lifecycle from registration to disposal, providing differentiated approaches for inter-agency sharing and conditional access control . Key contributions include systematic reflection of actual criminal justice procedures across South Korea, the United States, the European Union, and China; evidence lifecycle-based management; dynamic authority management for multi-party cooperation; and balance between procedural legitimacy and technical efficiency .
GAS4SEC proposes a framework for designing, validating, and deploying secure, cost-effective, and forensically sound blockchain-based evidence management systems. The system combines formally bound smart contract architecture with role-based access control, immutable evidence records, and custody processes to maintain authenticity, traceability, and accountability. The research includes systematic vulnerability analysis correlated with OWASP smart contract risks to address unauthorized access, logic abuse, and invalid state transitions . Deployed and tested on Polygon Layer-2 blockchain, the approach demonstrates scalable and cost-effective on-chain forensics operations without sacrificing security or forensic integrity .