Drifting Towards Better Error Probabilities in Fully Homomorphic Encryption

Researchers have developed new techniques to improve security and efficiency in Fully Homomorphic Encryption (FHE), which will be presented at EUROCRYPT 2025. The study addresses the challenge of balancing computational efficiency and strong security, particularly concerning decryption failure, which poses a vulnerability when moving from standard IND-CPA security to the more robust IND-CPA D security. The research introduces the concept of ciphertext drift, noting that traditional modulus switching operations contribute significantly to error growth in FHE schemes like FHEW, TFHE, and FINAL. By mitigating drift without increasing cryptographic parameters, the proposed methods enhance security without impacting performance. The introduction of sIND-CPA D, a stronger security model, further strengthens resilience against sophisticated adversaries. The findings suggest that existing FHE parameter sets can be optimized using these techniques, which have significant implications for privacy-preserving AI and secure data processing applications. The research will be showcased at EUROCRYPT 2025, and interested parties are invited to discuss its impact at the conference in Madrid.