A Threshold Cryptography Framework for Secure and Resilient Symmetric Key Management in Multi-Cloud Environments

Abstract

This paper addresses the critical security and availability risks inherent in centralized key management systems (KMS) for cloud data protection. The compromise or failure of a single KMS can lead to catastrophic data breaches or loss of access. We propose a decentralized framework to mitigate this single point of failure. Technology or Method: We introduce the Threshold Key Management System (TKMS), a novel framework that leverages threshold cryptography to manage symmetric encryption keys. The framework employs a (k, n)-threshold secret sharing scheme to shard a master symmetric key across n independent Key Management Nodes (KMNs), which are distributed across multiple cloud provider infrastructures. Key generation is performed collaboratively using a Distributed Key Generation (DKG) protocol, eliminating the need for a trusted dealer. Results: The security analysis demonstrates that TKMS guarantees key confidentiality as long as fewer than k KMNs are compromised. The system provides high availability, tolerating the failure of up to n − k nodes. The projected performance evaluation indicates that the cryptographic overhead is manageable and offers a favorable trade-off for the significantly enhanced security and resilience. Conclusions: TKMS presents a robust and fault-tolerant alternative to traditional cloud KMS. By distributing trust across multiple administrative domains, it significantly raises the bar for attackers and protects against provider-level failures. Impact: This work provides a practical blueprint for building highly secure, resilient, and trust-minimized data protection services in the cloud, with direct applications in securing sensitive corporate data, personal information, and critical infrastructure backups.