ISO 17090-5:2017

Overview

ISO 17090-5:2017 - Health informatics - Public key infrastructure - Part 5 - specifies procedural requirements for authenticating entities using Healthcare PKI (HPKI) credentials. The standard focuses on certificate validation processes used by healthcare information systems (including remote access). It clarifies how servers and client applications should validate digital certificates to reduce spoofing, impersonation and other identity-based risks. Authorization procedures and the data format of digital signatures are explicitly out of scope.

Key topics and technical requirements

• Scope and target systems
  • Applies to digital signature libraries and standalone or embedded digital signature creation/verification programs used in healthcare applications.
  • Does not cover application UI, cryptographic library layers (e.g., CSP or PKCS#11) or authorization protocols.
• Three-phase authentication model
  • Preparation phase: CA issues a certificate for the subscriber’s public key; trust anchor stored in a repository.
  • Configuration phase: Server retrieves and stores CA certificates as trust anchors.
  • Authentication phase: Challenge-response flow where the client signs a server-generated nonce with the subscriber’s private key; server retrieves revocation data and verifies signature and certificate.
• Validation elements (minimum checks)
  • Signature value: Verify signature created by the subscriber’s private key.
  • Trust anchor: Ensure certificate chains to a trusted CA stored on the server.
  • Revocation status: Check Certificate Revocation List (CRL) or equivalent (OCSP referenced) to detect revoked keys.
  • Validity date: Ensure certificate is within its valid date range (not expired).
  • Key usage / extensions: Confirm certificate is appropriate for authentication (not a test/demo certificate).
• Token security requirement
  • End-entity private keys should be stored on secure tokens (e.g., smart cards, USB tokens) conforming to requirements equivalent to FIPS 140-2 level 1 (see ISO 17090-3).

Practical applications and users

• Who uses it:
  • Health IT architects, PKI administrators, security officers, and developers of EHR/PHR systems and health information exchanges.
• Practical uses:
  • Implementing secure authentication for clinician access to EHRs, remote system access, cross-organization data exchange, and integration of digital signature verification into healthcare workflows.
  • Designing validation procedures to reduce identity fraud, spoofing, use of revoked/expired keys, and misuse of test certificates.

Related standards

• ISO 17090-1 - Overview of digital certificate services (normative reference).
• ISO 17090-3 - Token and key storage requirements (referenced for FIPS-equivalent requirements).
• The document is part of the ISO 17090 series on Healthcare PKI.

Keywords: ISO 17090-5:2017, Health informatics, Healthcare PKI, authentication, public key infrastructure, digital certificate validation, revocation, trust anchor, CRL, OCSP.