Method for verifying model update

The federated learning system includes a moderator and a plurality of client devices. Each client device performs a method for verifying model update as follows: receiving a hash function and a general model; training a client model according to the general model and raw data; computing a difference between the general model and the client model as an update parameter, sending the update parameter to the moderator so that the moderator receives a plurality of update parameters; inputting the update parameter to the hash function to generate a hash value; sending the hash value to other client devices, thereby receiving a plurality of hash values; summing all hash values to generate a trust value; receiving an aggregation parameter computed according to the update parameters by the moderator; inputting the aggregation parameter to the hash function to generate a to-be-verified value; and updating the client model according to the aggregation parameter when the to-be-verified value equals the trust value.