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The Internet holds both promise and peril for the communications of person-identifiable health information. Because of technical features designed to promote accessibility and interoperability rather than security, Internet addressing conventions and transport protocols are vulnerable to compromise by malicious persons and programs. In addition, most commonly used personal computer (PC) operating systems currently lack the hardware-based system software protection and process isolation that are essential for ensuring the integrity of trusted applications. Security approaches designed for electronic commerce, that trade known security weaknesses for limited financial liability, are not sufficient for personal health data, where the personal damage caused by unintentional disclosure may be far more serious. To overcome these obstacles, we are developing and evaluating an Internet-based communications system called PCASSO (Patient-centered access to secure systems online) that applies state of the art security to health information. PCASSO includes role-based access control, multi-level security, strong device and user authentication, session-specific encryption and audit trails. Unlike Internet-based electronic commerce 'solutions,' PCASSO secures data end-to-end: in the server; in the data repository; across the network; and on the client. PCASSO is designed to give patients as well as providers access to personal health records via the Internet.

The need for security protection in Internet-based healthcare applications is generally acknowledged. Most healthcare applications that use the Internet have at least implemented some kind of encryption. Most applications also enforce user authentication and access control policies, and many audit user actions. However, most fall short on providing strong assurances that the security mechanisms are behaving as expected and that they cannot be subverted. While no system can claim to be totally "bulletproof," PCASSO provides assurance of correct operation through formal, disciplined design and development methodologies, as well as through functional and penetration testing. Through its security mechanisms, backed by strong system assurances, PCASSO is demonstrating "safe" use of public data networks for health care.

The ubiquity and ease of use of the Web have made it an increasingly popular medium for communication of health-related information. Web interfaces to commercially available clinical information systems are now available or under development by most major vendors. To the extent that such interfaces involve the use of unprotected operating systems, they are vulnerable to security limitations of Web client software environments. The Patient Centered Access to Secure Systems Online (PCASSO) project extends the protections for person-identifiable health data on Web client computers. PCASSO uses several approaches, including physical protection of authentication information, execution containment, graphical displays, and monitoring the client system for intrusions and co-existing programs that may compromise security.

Patient Centered Access to Secure Systems Online (PCASSO) is a National Information Infrastructure research project funded by the US National Library of Medicine (NLM). PCASSO is specifically designed to address the problem of enabling secure access to health information over the Internet, not just for healthcare providers and medical researchers, but also for patients to view their own medical records. The project is using familiar Web technologies to support the search and retrieval of information, including patient demographics, medications, lab tests, and transcription reports. State-of-the-art security technologies protect patient privacy and the integrity of patient information. This paper describes the security architecture of the PCASSO system.

The Internet's World-Wide Web (WWW) provides an appealing medium for the communication of health related information due to its ease of use and growing popularity. But current technologies for communicating data between WWW clients and servers are systematically vulnerable to certain types of security threats. Prominent among these threats are "Trojan horse" programs running on client workstations, which perform some useful and known function for a user, while breaching security via background functions that are not apparent to the user. The Patient-Centered Access to Secure Systems Online (PCASSO) project of SAIC and UCSD is a research, development and evaluation project to exploit state-of-the-art security and WWW technology for health care. PCASSO is designed to provide secure access to clinical data for healthcare providers and their patients using the Internet. PCASSO will be evaluated for both safety and effectiveness, and may provide a model for secure communications via public data networks.