Boulder vs OpenXPKI

Boulder is an open-source ACME certificate authority written in Go and used to run Let’s Encrypt. ACME lets a certificate authority verify control of an identifier and allows subscribers to issue or revoke certificates for identifiers they control. Boulder divides its work among web front ends, registration and validation authorities, a certificate authority, storage authority, publisher, and CRL updater. These boundaries separate CA functions by security context, with the certificate authority receiving instructions from the registration authority. Components communicate through gRPC, and the software stores ACME accounts, authorizations, challenges, orders, and certificates. Boulder is free under the Mozilla Public License 2.0 and is listed for API, Linux, and self-hosted use. Maintainers recommend Docker and Docker Compose for development and experimentation, and document connecting Certbot or another ACME client to a local instance. That Docker environment is not suitable for production: it uses publicly available private key material, exposes debug ports, and is described as brittle when components fail. Boulder is built for Let’s Encrypt and Web PKI baseline requirements; maintainers say it often does not fit other organizations’ production needs.

OpenXPKI is PKI and Trustcenter software for managing X.509v3 certificates in professional environments. Its customizable workflows cover requests, renewals, and revocations, with enrollment through SCEP, EST, SimpleCMC, ACME, and a REST-like API with OpenAPI support. One instance can host multiple PKI Realms, each with separate namespaces, profiles, workflows, and policies. The Ember.js web interface serves users, operators, and administrators in major browsers. Connectors reach flat files, LDAP, SQL databases, and web services; Enterprise Edition adds extensions for DigiCert, Sectigo, and SwissSign. Hardware Security Modules are supported through PKCS#11. YAML configuration can be tracked with revision control, and custom reporting workflows can produce downloadable CSVs. Community Edition is free and fully functional, with Debian 12 packages and mailing-list support. Enterprise Edition has packages for RHEL, SLES, and Ubuntu Server LTS; service and commercial support options are also listed, with SLAs available. The software was founded in 2009.