Usability issues that exist in security APIs cause programmers to embed those security APIs incorrectly to the applications they develop. This results in introduction of security vulnerabilities to those applications. One of the main reasons for security APIs to be not usable is currently there is no proper method by which the usability issues of security APIs can be identified. We conducted a study to assess the effectiveness of the cognitive dimensions questionnaire based usability evaluation methodology in evaluating the usability of security APIs. We used a cognitive dimensions based generic questionnaire to collect feedback from programmers who participated in the study. Results revealed interesting facts about the prevailing usability issues in four commonly used security APIs and the capability of the methodology to identify those issues.