Optionally, the apparatus further includes the following: a ciphertext sending unit 94, configured to send homomorphic ciphertext c₀ to c_s respectively corresponding to data m₀ to m_s to a specified user, so that the specified user performs predetermined operation f( ) that satisfies additive homomorphism on homomorphic ciphertext c₀ to c_s; and the ciphertext decryption unit 92 is configured to receive and decrypt operation result f(c₀?c_s) returned by the specified user, where a value obtained after the decryption is f(m₀?m_s).

The system, apparatus, module, or unit illustrated in the previous implementations can be implemented by using a computer chip or an entity, or can be implemented by using a product having a certain function. A typical implementation device is a computer, and the computer can be a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email receiving and sending device, a game console, a tablet computer, a wearable device, or any combination of these devices.

In a typical configuration, the computer includes one or more processors (CPU), input/output interfaces, network interfaces, and memories.

The memory can include a non-persistent memory, a random access memory (RAM), a nonvolatile memory, and/or another form that are in a computer readable medium, for example, a read-only memory (ROM) or a flash memory (flash RAM). The memory is an example of the computer readable medium.