Future Internet Seminar- Winter Term 2012/2013 Chair for Network Architectures and Services

Secure connections on the Internet are crucial to many ap-plications. Nowadays infrastructure for securing connections on the Internet heavily relies on the X.509 public-key infra-structure (PKI), which is maintained by Certificate Author-ities (CAs). Recent attacks on CAs showed the fragility of the current X.509 system. In order to alleviate or entirely fix problems with the X.509 system, different techniques and systems have been pro-posed. The proposed systems can be categorized into 4 dif-ferent concepts: DNS-based, Pinning-based, Notary-based, and Transparency-based approaches. This paper gives an overview over these concepts and outlines their advantages and disadvantages. It also covers some of the best-known representatives of the concepts. Sovereign Keys, a Transparency-based approach, is discussed in detail