734 research outputs found
FairLedger: A Fair Blockchain Protocol for Financial Institutions
Financial institutions are currently looking into technologies for
permissioned blockchains. A major effort in this direction is Hyperledger, an
open source project hosted by the Linux Foundation and backed by a consortium
of over a hundred companies. A key component in permissioned blockchain
protocols is a byzantine fault tolerant (BFT) consensus engine that orders
transactions. However, currently available BFT solutions in Hyperledger (as
well as in the literature at large) are inadequate for financial settings; they
are not designed to ensure fairness or to tolerate selfish behavior that arises
when financial institutions strive to maximize their own profit.
We present FairLedger, a permissioned blockchain BFT protocol, which is fair,
designed to deal with rational behavior, and, no less important, easy to
understand and implement. The secret sauce of our protocol is a new
communication abstraction, called detectable all-to-all (DA2A), which allows us
to detect participants (byzantine or rational) that deviate from the protocol,
and punish them. We implement FairLedger in the Hyperledger open source
project, using Iroha framework, one of the biggest projects therein. To
evaluate FairLegder's performance, we also implement it in the PBFT framework
and compare the two protocols. Our results show that in failure-free scenarios
FairLedger achieves better throughput than both Iroha's implementation and PBFT
in wide-area settings
Model Checking Paxos in Spin
We present a formal model of a distributed consensus algorithm in the
executable specification language Promela extended with a new type of guards,
called counting guards, needed to implement transitions that depend on majority
voting. Our formalization exploits abstractions that follow from reduction
theorems applied to the specific case-study. We apply the model checker Spin to
automatically validate finite instances of the model and to extract
preconditions on the size of quorums used in the election phases of the
protocol.Comment: In Proceedings GandALF 2014, arXiv:1408.556
HammerHead: Leader Reputation for Dynamic Scheduling
The need for high throughput and censorship resistance in blockchain
technology has led to research on DAG-based consensus. The Sui blockchain
protocol uses a variant of the Bullshark consensus algorithm due to its lower
latency, but this leader-based protocol causes performance issues when
candidate leaders crash. In this paper, we explore the ideas pioneered by
Carousel on providing Leader-Utilization and present HammerHead. Unlike
Carousel, which is built with a chained and pipelined consensus protocol in
mind, HammerHead does not need to worry about chain quality as it is directly
provided by the DAG, but needs to make sure that even though validators might
commit blocks in different views the safety and liveness is preserved. Our
implementation of HammerHead shows a slight performance increase in a faultless
setting, and a drastic 2x latency reduction and up to 40% throughput increase
when suffering faults (100 validators, 33 faults)
Moving formal methods into practice. Verifying the FTPP Scoreboard: Results, phase 1
This report documents the Phase 1 results of an effort aimed at formally verifying a key hardware component, called Scoreboard, of a Fault-Tolerant Parallel Processor (FTPP) being built at Charles Stark Draper Laboratory (CSDL). The Scoreboard is part of the FTPP virtual bus that guarantees reliable communication between processors in the presence of Byzantine faults in the system. The Scoreboard implements a piece of control logic that approves and validates a message before it can be transmitted. The goal of Phase 1 was to lay the foundation of the Scoreboard verification. A formal specification of the functional requirements and a high-level hardware design for the Scoreboard were developed. The hardware design was based on a preliminary Scoreboard design developed at CSDL. A main correctness theorem, from which the functional requirements can be established as corollaries, was proved for the Scoreboard design. The goal of Phase 2 is to verify the final detailed design of Scoreboard. This task is being conducted as part of a NASA-sponsored effort to explore integration of formal methods in the development cycle of current fault-tolerant architectures being built in the aerospace industry
Self-stabilizing Byzantine Multivalued Consensus
Consensus, abstracting a myriad of problems in which processes have to agree
on a single value, is one of the most celebrated problems of fault-tolerant
distributed computing. Consensus applications include fundamental services for
the environments of the Cloud and Blockchain, and in such challenging
environments, malicious behaviors are often modeled as adversarial Byzantine
faults.
At OPODIS 2010, Mostefaoui and Raynal (in short MR) presented a
Byzantine-tolerant solution to consensus in which the decided value cannot be a
value proposed only by Byzantine processes. MR has optimal resilience coping
with up to t < n/3 Byzantine nodes over n processes. MR provides this
multivalued consensus object (which accepts proposals taken from a finite set
of values) assuming the availability of a single Binary consensus object (which
accepts proposals taken from the set {0,1}).
This work, which focuses on multivalued consensus, aims at the design of an
even more robust solution than MR. Our proposal expands MR's fault-model with
self-stabilization, a vigorous notion of fault-tolerance. In addition to
tolerating Byzantine, self-stabilizing systems can automatically recover after
the occurrence of arbitrary transient-faults. These faults represent any
violation of the assumptions according to which the system was designed to
operate (provided that the algorithm code remains intact).
To the best of our knowledge, we propose the first self-stabilizing solution
for intrusion-tolerant multivalued consensus for asynchronous message-passing
systems prone to Byzantine failures. Our solution has a O(t) stabilization time
from arbitrary transient faults.Comment: arXiv admin note: text overlap with arXiv:2110.0859
- …