307 research outputs found
Designing Proof of Human-work Puzzles for Cryptocurrency and Beyond
We introduce the novel notion of a Proof of Human-work (PoH) and present the first distributed consensus protocol from hard Artificial Intelligence problems. As the name suggests, a PoH is a proof that a {\em human} invested a moderate amount of effort to solve some challenge. A PoH puzzle should be moderately hard for a human to solve. However, a PoH puzzle must be hard for a computer to solve, including the computer that generated the puzzle, without sufficient assistance from a human. By contrast, CAPTCHAs are only difficult for other computers to solve --- not for the computer that generated the puzzle. We also require that a PoH be publicly verifiable by a computer without any human assistance and without ever interacting with the agent who generated the proof of human-work. We show how to construct PoH puzzles from indistinguishability obfuscation and from CAPTCHAs. We motivate our ideas with two applications: HumanCoin and passwords. We use PoH puzzles to construct HumanCoin, the first cryptocurrency system with human miners. Second, we use proofs of human work to develop a password authentication scheme which provably protects users against offline attacks
Foundations, Properties, and Security Applications of Puzzles: A Survey
Cryptographic algorithms have been used not only to create robust ciphertexts
but also to generate cryptograms that, contrary to the classic goal of
cryptography, are meant to be broken. These cryptograms, generally called
puzzles, require the use of a certain amount of resources to be solved, hence
introducing a cost that is often regarded as a time delay---though it could
involve other metrics as well, such as bandwidth. These powerful features have
made puzzles the core of many security protocols, acquiring increasing
importance in the IT security landscape. The concept of a puzzle has
subsequently been extended to other types of schemes that do not use
cryptographic functions, such as CAPTCHAs, which are used to discriminate
humans from machines. Overall, puzzles have experienced a renewed interest with
the advent of Bitcoin, which uses a CPU-intensive puzzle as proof of work. In
this paper, we provide a comprehensive study of the most important puzzle
construction schemes available in the literature, categorizing them according
to several attributes, such as resource type, verification type, and
applications. We have redefined the term puzzle by collecting and integrating
the scattered notions used in different works, to cover all the existing
applications. Moreover, we provide an overview of the possible applications,
identifying key requirements and different design approaches. Finally, we
highlight the features and limitations of each approach, providing a useful
guide for the future development of new puzzle schemes.Comment: This article has been accepted for publication in ACM Computing
Survey
An analysis and examination of consensus attacks in blockchain networks
This paper examines consensus attacks as they relate to blockchain networks. Consensus attacks are a significant threat to the security and integrity of blockchain networks, and understanding these attacks is crucial for developers and stakeholders. The primary contribution of the paper is to present blockchain and consensus attacks in a clear and accessible manner, with the aim of making these complex concepts easily understandable for a general audience. Using literature review, the paper identifies various methods to prevent consensus attacks, including multi-chain networks, proof-of-work consensus algorithms, and network auditing and monitoring. An analysis revealed that these methods for preventing consensus attacks are not mutually exclusive and can be used in conjunction with each other. Ultimately, the choice of which methods to implement depends on the specific needs and goals of the network being built. The paper concludes with a discussion of the implications of these findings for blockchain network development and security
The sustainability of blockchain
openBlockchain technology is considered one of the most fascinating technology in the last 20 years. Blockchain system needs improvements due to their problems as all technologies are needed in their lifetime. The major problems are the energy consumption level and CO2 emissions are released into the environment through mining activities. In this thesis, it will be discussed these issues and possible solutions about how to improve blockchain technology as being environmentally friendly
Designing Proof of Transaction Puzzles for Cryptocurrency
One of the Bitcoin\u27s innovations is the Proof of Work puzzle (aka scratch-off puzzle) as a consensus protocol for anonymous networks without pre-established PKI. Bitcoins based on the Proof of Work puzzle have been harshly blamed today for problems such as energy wasted and not easily scalable. In this paper, we construct a novel Proof of Transaction(PoT) puzzle, and prove that PoT puzzle satisfies the basic construction conditions of scratch-off puzzle. We also show construction of PoTcoin as application. PoTcoin has many advantage but not limited as strengthening the network topology, promoting currency circulation, anti-outsourcing computing and environment-friendly
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