The theoretical part of the Master thesis describes basic information about the key management and cryptographic libraries NSS (Network Security Services), GnuTLS, and OpenSSL. The practical part describes the design and the process of the experiment for the use of the NSS, GnuTLS and OpenSSL systems for management of cryptographic keys and public key certificates. In collaboration with the tutor and the consultant, we prepared individual tasks for the students of PA193 Secure Coding Principles and Practices of FI MU. Based on the results of this experiment the usability of the various systems was compared and specific improvements were suggested. The specific steps in performing the experiment for the DevConf 2017 conference in Brno were suggested as well. The wireframes of the graphical user interface of NSS for specialized cryptographic certificate operations were designed.