associating some kind of identity (e.g. a domain name or an email
address) with a public key. CAs are used with TLS and S/MIME
certificates, and the CA system has a big list of possible and real
-problems which are summarized in \cite{https13}.
+problems which are summarized in section \ref{sec:hardeningpki} and
+\cite{https13}.
The Web of Trust is a decentralized system where people sign each
others keys, so that there is a high chance that there is a ``trust