METHOD AND SERVER FOR EVALUATING A PROBABILITY OF AN OBSERVATION SEQUENCE STORED AT A CLIENT WITH RESPECT TO A HIDDEN MARKOV MODEL

摘要

A probability of an observation sequence stored at a client is evaluated securely with respect to a hidden Markov model (HMM) stored at a server. The server determines for each state of the HMM an encryption of a log probability of a current element of the observation sequence. Determines for each state an encryption of a log summation of a product of a likelihood of the observation sequence based on a previous element of the observation sequence and a transition probability to each state. Determines an encryption of a log likelihood of the observation sequence for each state as a product of the encryption of a log summation and an encryption of a corresponding log probability of the current element of the observation sequence. Determines an encryption of the log probability of the observation sequence based on the log likelihood of the observation sequence for each state.