Let's Encrypt vs XiPKI

Let’s Encrypt is a global Certificate Authority that provides SSL/TLS certificates for HTTPS connections. The ACME protocol verifies control of a domain, and compatible clients can automate issuance, management, and renewal. Its client directory includes Apache HTTP Server, Caddy, nginx, Kubernetes, Docker, and Windows/IIS environments. Certificates are Domain Validation only; Let’s Encrypt says it does not plan to issue Organization Validation or Extended Validation certificates. Wildcard certificates are available through the DNS-01 challenge. Standard certificates last 90 days, with an optional six-day lifetime; these periods cannot be adjusted. Subscribers generate and manage private keys on their own servers. Issued and revoked certificates are publicly recorded, and the service says its certificates are trusted by most browsers and operating systems. Certificates cost nothing. A registered domain can receive up to 50 certificates every seven days under published rate limits. Direct subscriber support is not offered.

XiPKI is an open-source public key infrastructure system for certification authority, registration authority, and OCSP responder functions, aimed at critical infrastructure. It supports multiple CAs in one instance, database clusters, and active instances for the same CA, with management through embedded OSGi commands and an API. Its CA gateway supports EST, SCEP, CMP, ACME, and its RESTful API. The OCSP responder handles RFC 2560, RFC 6960, and RFC 5019, along with signed and unsigned requests, health checks, and multiple certificate status sources. HSM connections use PKCS#11; listed devices include AWS CloudHSM, Nitrokey, nCipher, Sansec, SoftHSM, TASS, Thales, and Utimaco. The project describes native support for ML-DSA, ML-KEM, and composite post-quantum algorithms. XiPKI is free under Apache License 2.0. It supports Linux and macOS and requires Java 11 or later and Tomcat 10 or 11. Listed databases include DB2, MariaDB, MySQL, Oracle, PostgreSQL, H2, and HSQLDB.