November 2001

1
IHE Year 4,the basis for a security solution
Cor Loef Philips Medical Systems IHE Planning and
Technical Committee
2
Overview

• Why Information Security in Radiology?
• Requirements
• Proposed solution in IHE Year 4
• Is the a reasonable solution?

3
IHE year 4 collection of trusted nodes

• Local authentication of user (Userid, Password)
• Authentication of the remote node (digital
  certificates)
• Local access control
• Audit trail
• Time synchronization

System B
System A
Secure network
Secure domain
Secure domain
4
Selection of standards

• X.509 certificates for node identity and keys
• TCP/IP Transport Layer Security Protocol (TLS)
  for node authentication, and optional encryption
• Reliable Delivery for Syslog (RFC 3195)
• Network Time Protocol ( NTP) for time
  synchronization

5
Selection of standards

• Audit trail open issue events and content
• HL7 Security and Accountability SIGCommon Audit
  Message (informative document)
• ASTM PS 115 Provisional Standard Specification
  for Audit and Disclosure Logs for Use in Health
  Information Systems
• IHE in Technical Framework Use XML and vendor
  DTD for defined content

6
Next level of security

• Full user authentication between nodes, key
  management
• Much more functionality and detail in
  authorization ( role based, patient related ),
  using central directory service
• Encryption
• Digital signatures (Reporting function)
• De-identification
• Support for Secure media
• Intrusion Detection Systems

7
Background on RFC-3195

• Reliable replacement for BSD Syslog
• Provides BEEP message structure, store and
  forward transport, common mandatory fields, and
  an XML payload.
• Options for encryption and signatures.

8
Audit Trail

• RFC - Basic information fields.
• HL7 Security SIG - Information content
  recommendations for audit trails.
• Missing component - a DTD

9
DTD

• Joint or separate HL7 and DICOM DTDs?
• There will be variety vendor DTDs in any real
  network
• Audit management will be prepared for multiple
  DTDs
• It makes sense for WG 14 to define DICOM
  transaction related DTD

10
What level of detail to describe?

• IHE is recommending routine audit at the patient
  level
• C2, CAPP (DoD) require adjustable detail level
• normally high level surveillance
• very detailed for high risk items and for suspect
  users
• Is it reasonable to define messages at the
  levels
• patient, study, series, instance, DIMSE
• DTD is prepared for the future beyond IHE basic
  support.