Setup-Free Secure Search on Encrypted Data: Faster and Post-Processing Free

We present a novel secure search protocol on data and queries encrypted with Fully Homomorphic Encryption (FHE). Our protocol enables organizations (client) to (1) securely upload an unsorted data array x = (x[1], . . . , x[n]) to an untrusted honest-but-curious sever, where data may be uploaded over time and from multiple data-sources; and (2) securely issue repeated search queries q for retrieving the first element (i*, x[i*]) satisfying an agreed matching criterion i* = min { i ∈ [n] | IsMatch(x[i], q) = 1 }, as well as fetching the next matching elements with further interaction. For security, the client encrypts the data and queries with FHE prior to uploading, and the server processes the ciphertexts to produce the result ciphertext for the client to decrypt. Our secure search protocol improves over the prior state-of-the-art for secure search on FHE encrypted data (Akavia, Feldman, Shaul (AFS), CCS’2018) in achieving: