International Association
for Cryptologic Research

Homomorphic encryption (HE) allows for computations on encrypted data without requiring decryption. HE is commonly applied to outsource computation on private data. Due to the additional risks caused by data outsourcing, the ability to recover from losses is essential, but doing so on data encrypted under an HE scheme introduces additional challenges for recovery and usability. This work introduces X-Cipher, which aims to make HE data resilient by ensuring it is private and fault-tolerant simultaneously at all stages during data-outsourcing. X-Cipher allows for data recovery without decryption, and maintains its ability to recover and keep data private when a cluster server has been compromised. X-Cipher allows for reduced ciphertext storage overhead by introducing novel encoding and leveraging previously introduced ciphertext packing. X-Cipher's capabilities were evaluated on synthetic dataset, and compared to prior work to demonstrate X-Cipher enables additional security capabilities while enabling privacy-preserving outsourced computations.