912 research outputs found
Ouroboros: A Provably Secure Proof-of-Stake Blockchain Protocol
We present ``Ouroboros,\u27\u27 the first blockchain protocol based on
proof of stake with rigorous security guarantees. We
establish security properties for the protocol comparable to those
achieved by the bitcoin blockchain protocol. As the protocol
provides a ``proof of stake\u27\u27 blockchain discipline, it offers
qualitative efficiency advantages over blockchains based on proof
of physical resources (e.g., proof of work). We also present a
novel reward mechanism for incentivizing proof of stake protocols
and we prove that, given this mechanism, honest behavior is an
approximate Nash equilibrium, thus neutralizing attacks such as
selfish mining. We also present initial evidence of the
practicality of our protocol in real world settings by providing
experimental results on transaction confirmation and processing
QuickSync: A Quickly Synchronizing PoS-Based Blockchain Protocol
To implement a blockchain, we need a blockchain protocol for all the nodes to
follow. To design a blockchain protocol, we need a block publisher selection
mechanism and a chain selection rule. In Proof-of-Stake (PoS) based blockchain
protocols, block publisher selection mechanism selects the node to publish the
next block based on the relative stake held by the node. However, PoS
protocols, such as Ouroboros v1, may face vulnerability to fully adaptive
corruptions.
In this paper, we propose a novel PoS-based blockchain protocol, QuickSync,
to achieve security against fully adaptive corruptions while improving on
performance. We propose a metric called block power, a value defined for each
block, derived from the output of the verifiable random function based on the
digital signature of the block publisher. With this metric, we compute chain
power, the sum of block powers of all the blocks comprising the chain, for all
the valid chains. These metrics are a function of the block publisher's stake
to enable the PoS aspect of the protocol. The chain selection rule selects the
chain with the highest chain power as the one to extend. This chain selection
rule hence determines the selected block publisher of the previous block. When
we use metrics to define the chain selection rule, it may lead to
vulnerabilities against Sybil attacks. QuickSync uses a Sybil attack resistant
function implemented using histogram matching. We prove that QuickSync
satisfies common prefix, chain growth, and chain quality properties and hence
it is secure. We also show that it is resilient to different types of
adversarial attack strategies. Our analysis demonstrates that QuickSync
performs better than Bitcoin by an order of magnitude on both transactions per
second and time to finality, and better than Ouroboros v1 by a factor of three
on time to finality
Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks
As cryptographic tokens and altcoins are increasingly being built to serve as
utility tokens, the notion of useful work consensus protocols, as opposed to
number-crunching PoW consensus, is becoming ever more important. In such
contexts, users get rewards from the network after they have carried out some
specific task useful for the network. While in some cases the proof of some
utility or service can be proved, the majority of tasks are impossible to
verify. In order to deal with such cases, we design Proof-of-Prestige (PoP) - a
reward system that can run on top of Proof-of-Stake blockchains. PoP introduces
prestige which is a volatile resource and, in contrast to coins, regenerates
over time. Prestige can be gained by performing useful work, spent when
benefiting from services and directly translates to users minting power. PoP is
resistant against Sybil and Collude attacks and can be used to reward workers
for completing unverifiable tasks, while keeping the system free for the
end-users. We use two exemplar use-cases to showcase the usefulness of PoP and
we build a simulator to assess the cryptoeconomic behaviour of the system in
terms of prestige transfer between nodes.Comment: 2019 IEEE International Conference on Blockchain and Cryptocurrency
(ICBC 2019
Decentralized trust in the inter-domain routing infrastructure
Inter-domain routing security is of critical importance to the Internet since it prevents unwanted traffic redirections. The current system is based on a Public Key Infrastructure (PKI), a centralized repository of digital certificates. However, the inherent centralization of such design creates tensions between its participants and hinders its deployment. In addition, some technical drawbacks of PKIs delay widespread adoption. In this paper we present IPchain, a blockchain to store the allocations and delegations of IP addresses. IPchain leverages blockchains' properties to decentralize trust among its participants, with the final goal of providing flexible trust models that adapt better to the ever-changing geopolitical landscape. Moreover, we argue that Proof of Stake is a suitable consensus algorithm for IPchain due to the unique incentive structure of this use-case, and that blockchains offer relevant technical advantages when compared to existing systems, such as simplified management. In order to show its feasibility and suitability, we have implemented and evaluated IPchain's performance and scalability storing around 350k IP prefixes in a 2.5 GB chain.Peer ReviewedPostprint (published version
A Game-theoretic Approach for Provably-Uniform Random Number Generation in Decentralized Networks
Many protocols in distributed computing rely on a source of randomness,
usually called a random beacon, both for their applicability and security. This
is especially true for proof-of-stake blockchain protocols in which the next
miner or set of miners have to be chosen randomly and each party's likelihood
to be selected is in proportion to their stake in the cryptocurrency.
Current random beacons used in proof-of-stake protocols, such as Ouroboros
and Algorand, have two fundamental limitations: Either (i)~they rely on
pseudorandomness, e.g.~assuming that the output of a hash function is uniform,
which is a widely-used but unproven assumption, or (ii)~they generate their
randomness using a distributed protocol in which several participants are
required to submit random numbers which are then used in the generation of a
final random result. However, in this case, there is no guarantee that the
numbers provided by the parties are uniformly random and there is no incentive
for the parties to honestly generate uniform randomness. Most random beacons
have both limitations.
In this thesis, we provide a protocol for distributed generation of
randomness. Our protocol does not rely on pseudorandomness at all. Similar to
some of the previous approaches, it uses random inputs by different
participants to generate a final random result. However, the crucial difference
is that we provide a game-theoretic guarantee showing that it is in everyone's
best interest to submit uniform random numbers. Hence, our approach is the
first to incentivize honest behavior instead of just assuming it. Moreover, the
approach is trustless and generates unbiased random numbers. It is also
tamper-proof and no party can change the output or affect its distribution.
Finally, it is designed with modularity in mind and can be easily plugged into
existing distributed protocols such as proof-of-stake blockchains.Comment: 36 pages excluding reference. Game-theoretic Randomness for
Proof-of-Stake in MARBLE (2023
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