Recently the interests in NII, CALS/EC, and security are rapidly increasing. However, only one of the security issues for CALS implementation, i.e., the security for EDI implementation, has been presented in the literature. No comprehensive discussion about CALS security including other CALS applications exists. This paper intends to present such a comprehensive analysis for the security requirements and standards for the well-recognized two-phase CALS implementation. We present a framework for CALS security encompassing security protocols and systems that are arranged into the framework in terms of the CALS implementation phases, application systems, and communication modes. This framework is followed by brief descriptions of the security services and mechanisms for each CALS application.