@inproceedings{10324,
  abstract     = {Off-chain protocols (channels) are a promising solution to the scalability and privacy challenges of blockchain payments. Current proposals, however, require synchrony assumptions to preserve the safety of a channel, leaking to an adversary the exact amount of time needed to control the network for a successful attack. In this paper, we introduce Brick, the first payment channel that remains secure under network asynchrony and concurrently provides correct incentives. The core idea is to incorporate the conflict resolution process within the channel by introducing a rational committee of external parties, called wardens. Hence, if a party wants to close a channel unilaterally, it can only get the committee’s approval for the last valid state. Additionally, Brick provides sub-second latency because it does not employ heavy-weight consensus. Instead, Brick uses consistent broadcast to announce updates and close the channel, a light-weight abstraction that is powerful enough to preserve safety and liveness to any rational parties. We formally define and prove for Brick the properties a payment channel construction should fulfill. We also design incentives for Brick such that honest and rational behavior aligns. Finally, we provide a reference implementation of the smart contracts in Solidity.},
  author       = {Avarikioti, Zeta and Kokoris Kogias, Eleftherios and Wattenhofer, Roger and Zindros, Dionysis},
  booktitle    = {25th International Conference on Financial Cryptography and Data Security},
  isbn         = {9-783-6626-4330-3},
  issn         = {1611-3349},
  location     = {Virtual},
  pages        = {209--230},
  publisher    = {Springer Nature},
  title        = {{Brick: Asynchronous incentive-compatible payment channels}},
  doi          = {10.1007/978-3-662-64331-0_11},
  volume       = {12675 },
  year         = {2021},
}

@inproceedings{10325,
  abstract     = {Since the inception of Bitcoin, a plethora of distributed ledgers differing in design and purpose has been created. While by design, blockchains provide no means to securely communicate with external systems, numerous attempts towards trustless cross-chain communication have been proposed over the years. Today, cross-chain communication (CCC) plays a fundamental role in cryptocurrency exchanges, scalability efforts via sharding, extension of existing systems through sidechains, and bootstrapping of new blockchains. Unfortunately, existing proposals are designed ad-hoc for specific use-cases, making it hard to gain confidence in their correctness and composability. We provide the first systematic exposition of cross-chain communication protocols. We formalize the underlying research problem and show that CCC is impossible without a trusted third party, contrary to common beliefs in the blockchain community. With this result in mind, we develop a framework to design new and evaluate existing CCC protocols, focusing on the inherent trust assumptions thereof, and derive a classification covering the field of cross-chain communication to date. We conclude by discussing open challenges for CCC research and the implications of interoperability on the security and privacy of blockchains.},
  author       = {Zamyatin, Alexei and Al-Bassam, Mustafa and Zindros, Dionysis and Kokoris Kogias, Eleftherios and Moreno-Sanchez, Pedro and Kiayias, Aggelos and Knottenbelt, William J.},
  booktitle    = {25th International Conference on Financial Cryptography and Data Security},
  isbn         = {9-783-6626-4330-3},
  issn         = {1611-3349},
  location     = {Virtual},
  pages        = {3--36},
  publisher    = {Springer Nature},
  title        = {{SoK: Communication across distributed ledgers}},
  doi          = {10.1007/978-3-662-64331-0_1},
  volume       = {12675 },
  year         = {2021},
}