A portable acoustic signal (speech signal) preprocessing (SSP) device for accessing an automatic speech/speaker recognition (ASSR) server comprises a microphone for converting sound including speech, silence and background noise signals to analog signals; an analog signals to digital converter for converting the analog signals to digital signals; a digital signal processor (DSP) for generating feature vector data representing the digitized speech and silence/background noise, and for generating channel characterization signals; and an acoustic coupler for converting the feature vector data and the characterization signals to acoustic signals and coupling the acoustic signals to a communication channel to access the ASSR server to perform speech and speaker recognition at a remote location. The SSP device may also be configured to compress and encrypt data transmitted to the ASSR server via the DSP and encryption keys stored in a memory. The ASSR server receives the preprocessed acoustic signals to perform speech/speaker recognition by setting references, selecting appropriate decoding models and algorithms to decode the acoustic signals by modeling the channel transfer function from the channel characterization signals and processing the silence/background noise data to reduce word error rate for speech recognition and to perform accurate speaker recognition. A client/server system having the portable SSP device and the ASSR server can be used to remotely activate, reset, or change personal identification numbers (PINs) or user passwords for smartcards, magnetic cards, or electronic money cards.