Analysis of Longitudinal Changes of Certificate Chains

Abstract: Certificate validation is today a vital part of keeping communication secure over the internet. It allows secure daily communication for roughly 5 billion people using the internet. This is done by the help of Certificate Authorities, who use the technique of certificate validation chains for a more relentless validation and to widen the possibilities of secure communication. These chains have been in a changing process since the beginning, which has not been in a single direction. In this thesis, the changes in properties of the certificate chains are studied during the time period 2013 until 2021. The datasets of certificate chains are generated from the crt.sh database. The focus is put on finding changes in the length of the certificate chains and where in the chains these changes appear. Being able to understand and explain these changes is of great value in order to know about the further development of these chains and to predict the future direction that these chains might take. Based on the findings from the analysis of the chains included in the dataset, it was possible to conclude that the average length of the chains has increased over the time period. Though there have been special occasions in the industry-leading to decline in later years of the time period.The findings in this thesis indicates that what is important for the industry has changed. From having a focus on increasing the length to shift focus to shorten the length to provide better performance in terms of speed.