Future-Proofing Cloud Security Against Quantum Attacks: Risk, Transition, and Mitigation Strategies

Quantum Computing (QC) introduces a transformative threat to digital security, with the potential to compromise widely deployed classical cryptographic systems. This survey offers a comprehensive and systematic examination of quantumsafe security for Cloud Computing (CC), focusing on the vulnerabilities, transition strategies, and mitigation mechanisms required to secure cloud infrastructures in the quantum era. We evaluated the landscape of quantum threats across the entire CC stack, demonstrating how quantum algorithms can undermine classical encryption and compromise cloud security at multiple architectural layers. Using a structured risk assessment methodology based on the STRIDE model, we evaluate quantum-induced attack vectors and their impact on cloud environments. To address these challenges, we propose a layered security framework that integrates hybrid cryptographic transition strategies, cryptographic agility, and proactive risk mitigation. We analyze the preparation and implementation approaches of the major Cloud Service Providers (CSPs), including AWS, Azure and GCP, synthesizing platform-specific initiatives toward Post-Quantum Cryptography (PQC). Furthermore, we provide a detailed evaluation of standardized PQC algorithms, exploring their resilience to side-channel and active attacks within cloud-native deployments. This survey serves as a strategic reference for cloud architects, policymakers, and researchers, offering actionable insights for navigating the complex transition to quantum-resilient cloud systems. We conclude by identifying six key future research directions: standardization and interoperability, performance and scalability, implementation security, integration with emerging technologies, systemic preparedness, and crypto-agile migration frameworks.