In recent high-speed data moderns for use over PSTN or leased line, the data compression technique based on CCITT V.42bis Recommendation is of popular use along sith CCITT V.42 error control function. A remaining concern to advanced-application users is the protection against unintended eavesdropping. This paper proposes the architectural model on how the security mechanism should be adopted into the above mentioned error-correction/data compression moderns. Also, the functional definitions and the operational procedures are described in detail for possible implementation.