Byzantine agreement requires a set of parties in a distributed system to agree on a value even if some parties are maliciously misbehaving. A new protocol for Byzantine agreement in a completely asynchronous network is presented that makes use of new cryptographic protocols, specifically protocols for threshold signatures and coin-tossing. These cryptographic protocols have practical and provably secure implementations in the random oracle model. In particular, a coin-tossing protocol based on the Diffie-Hellman problem is presented and analyzed.The resulting asynchronous Byzantine agreement protocol is both practical and theoretically optimal because it tolerates the maximum number of corrupted parties, runs in constant expected rounds, has message and communication complexity close to the optimum, and uses a trusted dealer only once in a setup phase, after which it can process a virtually unlimited number of transactions.
Abstract. Broadcast protocols are a fundamental building block for implementing replication in fault-tolerant distributed systems. This paper addresses secure service replication in an asynchronous environment with a static set of servers, where a malicious adversary may corrupt up to a threshold of servers and controls the network. We develop a formal model using concepts from modern cryptography, give modular definitions for several broadcast problems, including reliable, atomic, and secure causal broadcast, and present protocols implementing them. Reliable broadcast is a basic primitive, also known as the Byzantine generals problem, providing agreement on a delivered message. Atomic broadcast imposes additionally a total order on all delivered messages. We present a randomized atomic broadcast protocol based on a new, efficient multi-valued asynchronous Byzantine agreement primitive with an external validity condition. Apparently, no such efficient asynchronous atomic broadcast protocol maintaining liveness and safety in the Byzantine model has appeared previously in the literature. Secure causal broadcast extends atomic broadcast by encryption to guarantee a causal order among the delivered messages. Our protocols use threshold cryptography for signatures, encryption, and coin-tossing.
Abstract-A PUF or Physical Unclonable Function is a function that is embodied in a physical structure that consists of many random uncontrollable components which originate from process variations during manufacturing. Due to this random structure a physical stimulus or challenge generates unpredictable responses. Because of their physical properties PUFs are unclonable and very promising primitives for the purpose of authentication and storage of cryptographic keys. Previous work on PUFs considers mainly static challenge-response PUFs. In many applications, however, a dynamic PUF would be desirable, e.g., in order to allow the key derived from the PUF to be updated.We define a new primitive, the reconfigurable PUF (rPUF) which is a PUF with a mechanism to transform it into a new PUF with a new unpredictable and uncontrollable challenge-response behavior, even if the challengeresponse behavior of the original PUF is already known. We present two practical instantiations of a reconfigurable PUF. One is a new variant of the optical PUF, and the other is based on phase change memory. We also illustrate how an rPUF can be used to protect non-volatile storage against invasive physical attacks.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.