Blockchain-Based Anonymization Methods with Smart Contract for Data Expiry: Toward GDPR-Compliant Lifecycle Management

Abstract

This paper introduces a privacy-preserving framework for blockchain systems using the Smart Contract for Data Expiry (SCDE). SCDE governs data registration, retention, and erasure through on-chain policies and off- chain encrypted storage. It combines AES-256 encryption, a Key Management System (KMS) for cryptographic erasure, and Zero-Knowledge Proofs (ZKPs) for verifiable deletion without revealing data. Decentralized Identifiers (DIDs) enable pseudonymization and user accountability. Comparative results show that traditional and off-chain approaches lack automated, verifiable erasure. SCDE achieves full GDPR compliance with moderate overhead, demonstrating that privacy, transparency, and immutability can coexist in decentralized environments