Abstract. Bitcoin is a distributed digital currency which has attracted a substantial number of users. We perform an in-depth investigation to understand what made Bitcoin so successful, while decades of research on cryptographic e-cash has not lead to a large-scale deployment. We ask also how Bitcoin could become a good candidate for a long-lived stable currency. In doing so, we identify several issues and attacks of Bitcoin, and propose suitable techniques to address them.

With the growing realization that current Internet protocols are reaching the limits of their senescence, a number of on-going research efforts aim to design potential next-generation Internet architectures. Although they vary in maturity and scope, in order to avoid past pitfalls, these efforts seek to treat security and privacy as fundamental requirements. Resilience to Denialof-Service (DoS) attacks that plague today's Internet is a major issue for any new architecture and deserves full attention.In this paper, we focus on DoS in a specific candidate nextgeneration Internet architecture called Named-Data Networking (NDN) -an instantiation of Information-Centric Networking approach. By stressing content dissemination, NDN appears to be attractive and viable approach to many types of current and emerging communication models. It also incorporates some basic security features that mitigate certain attacks. However, NDN's resilience to DoS attacks has not been analyzed to-date. This paper represents the first step towards assessment and possible mitigation of DoS in NDN. After identifying and analyzing several new types of attacks, it investigates their variations, effects and counter-measures. This paper also sheds some light on the long-standing debate about relative virtues of self-certifying, as opposed to human-readable, names.

Authentication of communication channels between devices that lack any previous association is an challenging problem. It has been considered in many contexts and in various flavors

The open and anonymous nature of a P2P network makes it an ideal medium for nttnckers to spread maliciuus content. In this paper: we describe a reputation-based trust management pmrocol fur P2P networks where users rate the reliability of parties they deal with, and share this information with their peers. The protocol helps estnblishing trust among goodpeers ns well as identibing the malicious ones. Results of various simulation experiments show that the proposed system can be highly effective in preventing the spread of malicious content in P2P networks.

As the Internet struggles to cope with scalability, mobility, and security issues, new network architectures are being proposed to better accommodate the needs of modern systems and applications. In particular, Content-Oriented Networking (CON) has emerged as a promising next-generation Internet architecture: it sets to decouple content from hosts, at the network layer, by naming data rather than hosts. CON comes with a potential for a wide range of benefits, including reduced congestion and improved delivery speed by means of content caching, simpler configuration of network devices, and security at the data level. However, it remains an interesting open question whether or not, and to what extent, this emerging networking paradigm bears new privacy challenges. In this paper, we provide a systematic privacy analysis of CON and the common building blocks among its various architectural instances in order to highlight emerging privacy threats, and analyze a few potential countermeasures. Finally, we present a comparison between CON and today's Internet in the context of a few privacy concepts, such as, anonymity, censoring, traceability, and confidentiality.Further, endpoint authentication mechanisms (whereby an endpoint can only authenticate the counterpart, but not the message) have been challenged by frequent attacks against SSL [34,42] and the hacking of certification authorities [46]. Also, the Internet today often struggles with mobility and resilience to disruption. Transport layer is, by design, unable to manage mobile parties and addon features -e.g., Mobile IPv6 (MIPv6) and Hierarchical MIPv6 [19] -have been suggested, albeit suffering from handoff latency and packet losses [26].Motivated by these issues, new architectures have been proposed, in the last few years, aiming to redesign the Internet (see, e.g., NSF's Future Internet Architecture multi-million program [57]), and accommodate content-oriented applications. In particular, Content-Oriented Networking (CON) [22] has set to decouple contents from hosts, at the network layer, by relying on the publish/subscribe paradigm. CON shifts identification from host to content, so that this can be located anywhere in the network. The content-centric communication paradigm introduced by CON relies on naming the content itself, rather than its location, and thus radically changes the way data is handled. Content is selfcontained, has a unique name, can be retrieved by means of an interest for that name, cached in any arbitrary location, and digitally signed to ensure its integrity and authenticity.