CertHat - Tools for Microsoft PKI is described as 'PKI solution based on Microsoft AD CS (Active Directory Certificate Services) offers a affordable and powerful digital certificates environment, however sometimes it can be challenging to use without additional tools (3rd party utilities or scripts)'. There are nine alternatives to CertHat - Tools for Microsoft PKI for a variety of platforms, including Windows, Linux, Self-Hosted solutions, Mac and Online / Web-based. The best alternative is xca - X Certificate and Key management, which is both free and Open Source. Other great apps like CertHat - Tools for Microsoft PKI are Smallstep Certificates (Free, Open Source), EJBCA (Freemium, Open Source), VeriSign (Paid) and OpenXPKI (Free, Open Source).
X Certificate and Key management is an interface for managing asymetric keys like RSA or DSA. It is intended as a small CA for creation and signing certificates. It uses the OpenSSL library for the cryptographic operations.
The Dogtag Certificate System is an enterprise-class open source Certificate Authority (CA). It supports all aspects of certificate lifecycle management, including key archival, OCSP and smartcard management, and much more.