An architecture for security-oriented perfective maintenance of legacy software

This work presents an implementation strategy which exploits separation of concerns and reuse in a multi-tier architecture to improve the security (availability, integrity, and confidentiality) level of an existing application. Functional properties are guaranteed via wrapping of the existing software modules. Security mechanisms are handled by the business logic of the middle-tier: availability and integrity are achieved via replication of the functional modules, confidentiality is obtained via cryptography. The technique is presented with regard to a case study application. We believe our experience can be used as a guideline for software practitioners to solve similar problems. We thus describe the conceptual model behind the architecture, discuss implementation issues, and present technical solutions.