1. A computer-implemented method for Joint Factor Analysis (JFA) scoring in speech processing systems performed by a computerized device, comprising: carrying out an enrollment session offline to enroll a speaker model in a speech processing system using JFA, including: providing an equation for calculating a score representative of the extent to which a speaker of a received test speech signal matches an enrolled speaker, based on speaker factors, a first component of channel factors which loosely depend on the test speech signal and a second component of channel factors which strongly depend on the test speech signal; receiving an enrollment speech signal from a user; extracting the speaker factors from the enrollment speech signal; estimating one or more values of the first component of channel factors from the enrollment speech signal, without using a test speech signal; carrying out a test session including: receiving a test speech signal; retrieving an estimated first component of channel factors which was estimated in the enrollment session without using the test speech signal, for the received test speech signal; calculating the second component of channel factors strongly dependent on the test session, based on the test speech signal; and generating a score based on the provided equation, the speaker factors, the estimated first component and the calculated second component of channel factors.