Chaodong Zheng

Bio: Chaodong Zheng is an academic researcher from Nanjing University. The author has contributed to research in topics: Jamming & Node (networking). The author has an hindex of 5, co-authored 22 publications receiving 833 citations. Previous affiliations of Chaodong Zheng include University of Freiburg & National University of Singapore.

A Secure Sharding Protocol For Open Blockchains

Abstract: Cryptocurrencies, such as Bitcoin and 250 similar alt-coins, embody at their core a blockchain protocol --- a mechanism for a distributed network of computational nodes to periodically agree on a set of new transactions. Designing a secure blockchain protocol relies on an open challenge in security, that of designing a highly-scalable agreement protocol open to manipulation by byzantine or arbitrarily malicious nodes. Bitcoin's blockchain agreement protocol exhibits security, but does not scale: it processes 3--7 transactions per second at present, irrespective of the available computation capacity at hand. In this paper, we propose a new distributed agreement protocol for permission-less blockchains called ELASTICO. ELASTICO scales transaction rates almost linearly with available computation for mining: the more the computation power in the network, the higher the number of transaction blocks selected per unit time. ELASTICO is efficient in its network messages and tolerates byzantine adversaries of up to one-fourth of the total computational power. Technically, ELASTICO uniformly partitions or parallelizes the mining network (securely) into smaller committees, each of which processes a disjoint set of transactions (or "shards"). While sharding is common in non-byzantine settings, ELASTICO is the first candidate for a secure sharding protocol with presence of byzantine adversaries. Our scalability experiments on Amazon EC2 with up to $1, 600$ nodes confirm ELASTICO's theoretical scaling properties.

SCP: A Computationally-Scalable Byzantine Consensus Protocol For Blockchains

Abstract: In this paper, we design a new blockchain Byzantine consensus protocol SCP where the throughput scales nearly linearly with the computation: the more computing power available, the more blocks selected per unit time. SCP is also efficient that the number of messages it requires is nearly linear in the network size. The computational scalability property offers the flexibility to tune bandwidth consumption by adjusting computational parameters (e.g., proof-of-work difficulty). The key ideas lie in securely establishing identities for network participants, randomly placing them in several committees and running a classical consensus protocol within each committee to propose blocks in parallel. We further design a mechanism to allow reaching consensus on blocks without broadcasting actual block data, while still enabling efficient block verification. We prove that our protocol is secure, efficient and applicable to several case studies. We conduct scalability experiments on Amazon EC2 with upto 80 cores, and confirm that SCP matches its theoretical scaling properties.

SybilCast: Broadcast on the Open Airwaves

Abstract: Consider a scenario where many wireless users are attempting to download data from a single base station. While most of the users are honest, some users may be malicious and attempt to obtain more than their fair share of the bandwidth. One possible strategy for attacking the system is to simulate multiple fake identities, each of which is given its own equal share of the bandwidth. Such an attack is often referred to as a sybil attack. To counter such behavior, we propose SybilCast, a protocol for multichannel wireless networks that limits the number of fake identities and, in doing so, ensures that each honest user gets at least a constant fraction of his or her fair share of the bandwidth. As a result, each honest user can complete his or her data download in asymptotically optimal time. A key aspect of this protocol is balancing the rate at which new identities are admitted and the maximum number of fake identities that can coexist while keeping the overhead low. Besides sybil attacks, our protocol can also tolerate spoofing and jamming.

Who Are You? Secure Identities in Ad Hoc Networks

Abstract: Sybil attacks occur when malicious users create multiple fake identities to gain an advantage over honest users. Wireless ad hoc networks are particularly vulnerable to these attacks because the participants are not known in advance, and they use an open and shared communication medium. In this paper, we develop algorithms that thwart sybil attacks in multi-channel wireless ad hoc networks using radio resource testing strategies. In particular, we describe and analyze new anti-sybil algorithms that guarantee, with high probability, that each honest device accepts a set of trusted and unforgeable identities that include all other honest devices and a bounded number of fake (sybil) identities. The proposed algorithms provide trade-offs between time complexity and sybil bounds. We also note that these algorithms solve, as subroutines, two problems of independent interest in this anonymous wireless setting: Byzantine consensus and network size estimation.

SybilCast: broadcast on the open airwaves (extended abstract)

Abstract: Consider a scenario where many wireless users are attempting to download data from a single base station. While most of the users are honest, some users may be malicious and attempt to obtain more than their fair share of the bandwidth. One possible strategy for attacking the system is to simulate multiple fake identities, each of which is given its own equal share of the bandwidth. Such an attack is often referred to as a sybil attack. To counter such behavior, we propose SybilCast, a protocol for multichannel wireless networks that limits the number of fake identities, and in doing so, ensures that each honest user gets at least a constant fraction of their fair share of the bandwidth. As a result, each honest user can complete his or her data download in asymptotically optimal time. A key aspect of this protocol is balancing the rate at which new identities are admitted and the maximum number of fake identities that can co-exist, while keeping the overhead low. Besides sybil attacks, our protocol can also tolerate spoofing and jamming.

A Secure Sharding Protocol For Open Blockchains

Abstract: Cryptocurrencies, such as Bitcoin and 250 similar alt-coins, embody at their core a blockchain protocol --- a mechanism for a distributed network of computational nodes to periodically agree on a set of new transactions. Designing a secure blockchain protocol relies on an open challenge in security, that of designing a highly-scalable agreement protocol open to manipulation by byzantine or arbitrarily malicious nodes. Bitcoin's blockchain agreement protocol exhibits security, but does not scale: it processes 3--7 transactions per second at present, irrespective of the available computation capacity at hand. In this paper, we propose a new distributed agreement protocol for permission-less blockchains called ELASTICO. ELASTICO scales transaction rates almost linearly with available computation for mining: the more the computation power in the network, the higher the number of transaction blocks selected per unit time. ELASTICO is efficient in its network messages and tolerates byzantine adversaries of up to one-fourth of the total computational power. Technically, ELASTICO uniformly partitions or parallelizes the mining network (securely) into smaller committees, each of which processes a disjoint set of transactions (or "shards"). While sharding is common in non-byzantine settings, ELASTICO is the first candidate for a secure sharding protocol with presence of byzantine adversaries. Our scalability experiments on Amazon EC2 with up to $1, 600$ nodes confirm ELASTICO's theoretical scaling properties.

The Quest for Scalable Blockchain Fabric: Proof-of-Work vs. BFT Replication

Abstract: Bitcoin cryptocurrency demonstrated the utility of global consensus across thousands of nodes, changing the world of digital transactions forever. In the early days of Bitcoin, the performance of its probabilistic proof-of-work (PoW) based consensus fabric, also known as blockchain, was not a major issue. Bitcoin became a success story, despite its consensus latencies on the order of an hour and the theoretical peak throughput of only up to 7 transactions per second.

Enabling Localized Peer-to-Peer Electricity Trading Among Plug-in Hybrid Electric Vehicles Using Consortium Blockchains

Abstract: We propose a localized peer-to-peer (P2P) electricity trading model for locally buying and selling electricity among plug-in hybrid electric vehicles (PHEVs) in smart grids Unlike traditional schemes, which transport electricity over long distances and through complex electricity transportation meshes, our proposed model achieves demand response by providing incentives to discharging PHEVs to balance local electricity demand out of their own self-interests However, since transaction security and privacy protection issues present serious challenges, we explore a promising consortium blockchain technology to improve transaction security without reliance on a trusted third party A localized P 2P E lectricity T rading system with CO nsortium blockchai N (PETCON) method is proposed to illustrate detailed operations of localized P2P electricity trading Moreover, the electricity pricing and the amount of traded electricity among PHEVs are solved by an iterative double auction mechanism to maximize social welfare in this electricity trading Security analysis shows that our proposed PETCON improves transaction security and privacy protection Numerical results based on a real map of Texas indicate that the double auction mechanism can achieve social welfare maximization while protecting privacy of the PHEVs

OmniLedger: A Secure, Scale-Out, Decentralized Ledger via Sharding

Abstract: Designing a secure permissionless distributed ledger (blockchain) that performs on par with centralized payment processors, such as Visa, is a challenging task. Most existing distributed ledgers are unable to scale-out, i.e., to grow their total processing capacity with the number of validators; and those that do, compromise security or decentralization. We present OmniLedger, a novel scale-out distributed ledger that preserves longterm security under permissionless operation. It ensures security and correctness by using a bias-resistant public-randomness protocol for choosing large, statistically representative shards that process transactions, and by introducing an efficient cross-shard commit protocol that atomically handles transactions affecting multiple shards. OmniLedger also optimizes performance via parallel intra-shard transaction processing, ledger pruning via collectively-signed state blocks, and low-latency "trust-but-verify" validation for low-value transactions. An evaluation of our experimental prototype shows that OmniLedger’s throughput scales linearly in the number of active validators, supporting Visa-level workloads and beyond, while confirming typical transactions in under two seconds.

Consortium Blockchain for Secure Energy Trading in Industrial Internet of Things

Abstract: In industrial Internet of things (IIoT), peer-to-peer (P2P) energy trading ubiquitously takes place in various scenarios, e.g., microgrids, energy harvesting networks, and vehicle-to-grid networks. However, there are common security and privacy challenges caused by untrusted and nontransparent energy markets in these scenarios. To address the security challenges, we exploit the consortium blockchain technology to propose a secure energy trading system named energy blockchain. This energy blockchain can be widely used in general scenarios of P2P energy trading getting rid of a trusted intermediary. Besides, to reduce the transaction limitation resulted from transaction confirmation delays on the energy blockchain, we propose a credit-based payment scheme to support fast and frequent energy trading. An optimal pricing strategy using Stackelberg game for credit-based loans is also proposed. Security analysis and numerical results based on a real dataset illustrate that the proposed energy blockchain and credit-based payment scheme are secure and efficient in IIoT.