1,666 research outputs found
Cob: a leaderless protocol for parallel Byzantine agreement in incomplete networks
No full textIn this paper we extend the Multidimensional Byzantine Agreement (MBA) Protocol, a leaderless Byzantine agreement for lists of arbitrary values, into a protocol suitable for wide gossiping networks: Cob. This generalization allows the consensus process to be run by an incomplete network of nodes provided with (non-synchronized) same-speed clocks. Not all nodes are active in every step, so the network size does not hamper the efficiency, as long as the gossiping broadcast delivers the messages to every node in reasonable time. These network assumptions model more closely real-life communication channels, so Cob may be applicable to a variety of practical problems, such as blockchain platforms implementing sharding. Cob has the same Bernoulli-like distribution that upper-bounds the number of steps as the MBA protocol. We prove its correctness and security assuming a supermajority of honest nodes in the network, and compare its performance with Algorand
Extensible decentralized secret sharing and application to Schnorr signatures
No full textStarting from links between Coding Theory and Secret Sharing Schemes, we develop an extensible and decentralized version of Shamir Secret Sharing, that allows the addition of new users after the initial share distribution. On top of it we design a totally decentralized (t, n)-threshold Schnorr signature scheme that needs only t users online during the key generation phase, while the others join later. Under standard assumptions we prove our scheme secure against adaptive malicious adversaries. Furthermore, we show how our security notion can be strengthened when considering a rushing adversary. Using a classical game-based argument, we prove that if there is an adversary capable of forging the scheme with non-negligible probability, then we can build a forger for the centralized Schnorr scheme with non-negligible probability
A Provably-Unforgeable Threshold Schnorr Signature With an Offline Recovery Party
No full textThe increase in the interest in cryptocurrencies, and the consequent need for technological
maturity of blockchain-based platforms, has been the fuel for some recent advances in cryptographic research. In this context, digital signature protocols have a central role since they guarantee ownership and control of digital assets.
The absence of trusted central authorities in public blockchains, which is the very foundation of this technology, poses some interesting challenges on the management of digital identities. In particular, the computational infeasibility of restoring a lost key is a threat to anyone possessing this kind of digital assets. A possible solution to this problem is to use threshold multi-signatures,
partially relying on a recovery-party whose only role, even though of paramount importance, is to intervene in case of key loss.
We present a Schnorr multi-party digital signature scheme that supports an offline participant during the key-generation phase, without relying on a trusted third party. Under standard assumptions we prove our scheme secure against adaptive malicious adversaries and capable of achieving the resiliency of the recovery in the presence of a malicious party
The Pottesman Collection in the British Museum. Early Dynastic and Sargonic administrative texts. With an Appendix on a Palmyrene Inscription
No full textEdizione, trascrizione, traduzione e commento di un frammento di iscrizione palmirena inedita presente nella collezione Pottesman del British Museum (Appendice Agostini).The British Museum houses a small collection of six cuneiform tablets and a Palmyrene dedicatory inscription purchased in 1987 from the private collection of Solomon Pottesman. The aim of the present contribution is to provide a catalog of this lot and an edition of the so far unpublished cuneiform texts. In the appendix, Alessio Agostini added the edition of the Palmyrene inscription, which would have otherwise gone beyond the capabilities of the present author
Electronic Attacks as a Cyber False Flag against Maritime Radars Systems
No full textRadar systems have long been essential for safe navigation in various transportation sectors, including aviation, maritime, and automotive. While these systems provide invaluable situational awareness and decision-making capabilities, they increasingly become targets for malicious actors aiming to disrupt their normal operations. Electronic countermeasures (ECM) have traditionally been the predominant form of attack. However, recent findings have uncovered their vulnerability to cyber-based actions, capitalizing on their digitization and network connectivity. In this paper, we propose a novel threat model that exploits cyber attack capabilities against radar systems to simulate the effects of ECM. This model goes beyond known attacks by introducing a deceptive element, challenging attribution. To evaluate the feasibility of these attacks, extensive experimentation is conducted using a realistic case study involving the maritime domain. Through this research, we aim to highlight the evolving threats facing radar systems and the need for comprehensive security measures
Provably Unforgeable Threshold EdDSA with an Offline Participant and Trustless Setup
No full textWe present an EdDSA-compatible multi-party digital signature scheme that supports an offline participant during the key-generation phase, without relying on a trusted third party. Under standard assumptions, we prove our scheme secure against adaptive malicious adversaries. Using a classical game-based argument, we prove that if there is an adversary capable of forging the scheme with non-negligible probability, then we can build a forger for the original EdDSA scheme with non-negligible probability. The scheme requires only two communication rounds in the signature generation phase and avoids expensive multi-party evaluation of cryptographic hash functions. We present our solution in a setting where two parties generate the keys and compute signatures, with a third party which can be brought online after the key generation when one of the other parties becomes unavailable. This setting is a perfect fit for custodial solutions where partially trusted services are employed by a user to increase resiliency. We provide also a possible solution to retain the resiliency of the recovery in the presence of a malicious party
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