Ensuring the confidentiality and privacy of sensitive information in cloud computing and outsourced databases is crucial. Homomorphic encryption (HE) offers a solution by enabling computations on encrypted data without decryption, allowing secure outsourcing while maintaining data confidentiality. However, HE faces performance challenges in query-intensive databases. To address this, we propose two novel optimizations, Silca and SilcaZ, tailored to outsourced databases in cloud computing. Silca utilizes a singular caching technique to reduce computational overhead, while SilcaZ leverages modular arithmetic operations to ensure the applicability of singular caching for intensive HE operations. We prove the semantic security of Silca and SilcaZ and implement them with CKKS and BGV in HElib as MySQL loadable functions. Extensive experiments with seven real-world datasets demonstrate their superior performance compared to existing HE schemes, bridging the gap between theoretical advancements and practical applications in applying HE schemes on outsourced databases in cloud computing.

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