Certificate
A digital certificate is an electronic document that uses public-key cryptography to verify the identity of an individual, organization, or server. In the z/OS environment, it primarily serves to establish secure communication channels, authenticate entities, and ensure data integrity and non-repudiation across mainframe applications and network services.
Key Characteristics
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- X.509 Standard: Mainframe digital certificates conform to the ITU-T X.509 standard, defining their format and content, including the public key, owner's identity, issuer's signature, and validity period.
- Public Key Infrastructure (PKI) Component: Certificates are integral to a PKI, relying on a trusted Certificate Authority (CA) to issue and manage them, thereby establishing a chain of trust.
- Key Rings: On z/OS, certificates and their associated private keys are often stored in logical collections called
key rings, which are managed by security managers like RACF. - Authentication and Encryption: They enable strong authentication by binding a public key to an identity and facilitate secure data exchange through encryption protocols like TLS/SSL.
- Validity Period: Each certificate has a defined start and end date, after which it expires and becomes invalid, requiring renewal or replacement.
- Revocation Mechanisms: Certificates can be revoked before their expiration date if their security is compromised, typically managed via Certificate Revocation Lists (CRLs) or Online Certificate Status Protocol (OCSP).
Use Cases
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- Secure Network Communication (TLS/SSL): Used extensively by z/OS applications like CICS, DB2, IMS, and MQ to establish encrypted and authenticated sessions over TCP/IP, protecting data in transit.
- Client and Server Authentication: Authenticating client applications or users connecting to z/OS services, and conversely, authenticating z/OS servers to external clients.
- Digital Signatures: Providing non-repudiation for transactions or data, where a private key signs data, and the corresponding public key in the certificate verifies the signature.
- VPN and IPSec: Securing virtual private network connections and IP Security (IPSec) tunnels between z/OS and other network endpoints.
- Secure FTP and SFTP: Enabling secure file transfers to and from the mainframe using protocols that leverage certificates for authentication and encryption.
Related Concepts
Digital certificates are fundamentally managed by RACF (Resource Access Control Facility) or other SAF (System Authorization Facility)-compliant security products on z/OS. RACF is responsible for defining, storing, and managing certificates within its database, linking them to users, and associating them with key rings. They are essential for implementing TLS/SSL (Transport Layer Security/Secure Sockets Layer), which provides secure communication for many mainframe subsystems like CICS, DB2, IMS, and MQ. The underlying cryptographic principles involve public key cryptography, where the certificate contains the public key, and the corresponding private key is securely stored.
- Centralized Management: Utilize RACF or an equivalent SAF-compliant security product for centralized management of all digital certificates and key rings on z/OS to ensure consistency and control.
- Strong Private Key Protection: Ensure that private keys associated with certificates are highly protected, stored securely (e.g., in hardware security modules - HSMs), and never exposed.
- Regular Renewal and Monitoring: Implement a robust process for tracking certificate expiration dates and renewing them well in advance to prevent service disruptions.
- Implement Revocation Mechanisms: Configure and regularly update Certificate Revocation Lists (CRLs) or use Online Certificate Status Protocol (OCSP) to promptly revoke compromised certificates.
- Least Privilege Access: Grant access to key rings and the ability to manage certificates only to authorized personnel and applications based on the principle of least privilege.