  Be it in the IoT or automotive domain, implicit certificates are gaining ever
more prominence in constrained embedded devices. They present a
resource-efficient security solution against common threat concerns. The
computational requirements are not the main issue anymore. The focus is now
placed on determining a good balance between the provided security level and
the derived threat model. A security aspect that often gets overlooked is the
establishment of secure communication sessions, as most design solutions are
based only on the use of static key derivation, and therefore, lack the perfect
forward secrecy. This leaves the transmitted data open for potential future
exposures by having keys tied to the certificates rather than the communication
sessions. We aim to patch this gap, by presenting a design that utilizes the
Station to Station (STS) protocol with implicit certificates. In addition, we
propose potential protocol optimization implementation steps and run a
comprehensive study on the performance and security level between the proposed
design and the state-of-the-art key derivation protocols. In our comparative
study, we show that with a slight computational increase of 20\% compared to a
static ECDSA key derivation, we are able to mitigate many session-related
security vulnerabilities that would otherwise remain open.
