Alibaba Group Holding Limited
HOMOMORPHIC DATA DECRYPTION METHOD AND APPARATUS FOR IMPLEMENTING PRIVACY PROTECTION

Abstract:

A computer-implemented method, non-transitory, computer-readable medium, and computer-implemented system are provided for implementing privacy protection. In an implementation, a public key pk={N, h} corresponding to a target user is obtained, where h is a generator of a predetermined cyclic group with a size of k in a random number space Z*.sub.N, a length of k is i bits, a length of N is n bits, and i<<n. A random number r is selected, so that h.sup.r belongs to the predetermined cyclic group. To-be-encrypted data m, corresponding to the target user using the public key pk and the random number r, is processed to generate a homomorphic ciphertext c=(1+N).sup.m(h.sup.N mod N.sup.2).sup.r mod N.sup.2. The homomorphic ciphertext c is provided to the target user, where the homomorphic ciphertext c can be decrypted using a private key sk to obtain the data m.