The Automated Certificate Management Environment (ACME) protocol, defined in RFC 8555, is a widely used protocol for automating the certificate issuance and management process. ACME eliminates the need for manual interactions in certificate lifecycle operations, making it well-suited for IoT devices, cloud services, and other automated environments.
ACME is primarily designed for Public Key Infrastructure (PKI) deployments that require automated certificate provisioning, renewal, and revocation. It enables clients to communicate with a certificate authority (CA) using a standardized, secure, and automated process.
Wichtig
Device Trust Manager uses ACME to issue certificates from certificate authorities (CAs) that are connected to private trust Root CAs. Because of this, Device Trust Manager does not implement the domain validation portion of the ACME protocol. Domain validation is typically required for certificates issued by publicly trusted CAs. However, since Device Trust Manager is used for private PKI deployments where domain validation is unnecessary, this step is skipped.
Automated certificate issuance: ACME automates the process of requesting and obtaining certificates, reducing the need for manual intervention.
Challenge-based Authorization: The protocol typically verifies control over a domain using challenges. Domain validation is not implemented in Device Trust Manager as it is not necessary for issuing certificates from private trust CAs.
Automated certificate renewal: ACME allows clients to automatically renew certificates before they expire, ensuring uninterrupted security.
RESTful API communication: ACME operates over HTTPS and uses JSON-based messages for structured communication between clients and the CA.
Cryptographic proof-of-control: Clients use cryptographic signatures to prove ownership of the private key associated with a certificate request.
IoT device identity management: Securely provisioning and managing certificates for connected devices to establish trust.
Enterprise PKI deployments: Automating certificate issuance within organizations using a private CA hierarchy.
Cloud service authentication: Enabling cloud-based services to obtain and manage certificates without manual intervention.
DevOps and CI/CD pipelines: Automating certificate provisioning for secure application deployment.
Authentication handshake
Device Trust Manager generates an HMAC and Key ID.
The HMAC and Key ID are entered into the ACME client configuration.
The ACME client generates a key pair.
The ACME client connects to the ACME Service and uses the HMAC and Key ID to pass its public key to the ACME Service.
Certificate request and issuance
The client submits a certificate signing request (CSR) to the CA through ACME.
The CA processes the request and issues the certificate, provided all requirements are met.
Anmerkung
Domain validation is not required for private trust CAs in Device Trust Manager.
Certificate renewal
Before expiration, the ACME client automatically requests a renewal.
The CA verifies the request and issues a new certificate.
Certificate revocation
The ACME client can request certificate revocation when a key compromise or decommissioning occurs.
The CA processes the revocation request and updates its certificate status.
Private CA trust model: ACME in Device Trust Manager is designed for private PKI deployments; what this means is certificates will not be trusted by public browsers or operating systems unless explicitly added to the trust store.
No domain validation requirements: Unlike public ACME implementations (for example, Let's Encrypt, which is a free, automated, and open Certificate Authority), Device Trust Manager does not require domain validation, simplifying the certificate issuance process for IoT and enterprise environments.
Automation readiness: Organizations should ensure their infrastructure supports automated certificate issuance and renewal through ACME.
Security best practices: Proper key management, access controls, and monitoring should be implemented to prevent unauthorized certificate requests.
ACME provides a streamlined, automated approach to certificate management, making it highly beneficial for device identity provisioning and enterprise PKI automation.
Device Trust Manager's ACME implementation focuses on private trust CA issuance, removing the need for domain validation while maintaining security and efficiency. By leveraging ACME, organizations can enhance security, reduce operational overhead, and ensure continuous certificate availability.