852 research outputs found
Mental Card Gaming Protocols Supportive Of Gameplay Versatility, Robustness And Efficiency
Pennainan kad mental merupakan protokol kriptografi yang membolehkan pennainan yang
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disahkan adil di kalangan parti-parti jauh yang penyangsi dan berpotensi menipu. Pennainan
kad ini setidak-tidaknya patut menyokong-tanpa memperkenal~an parti ketiga yang dipercayai
(TTP)--rahsia kad, pengesanan penipuan dan keselamatan bersyarat ke atas pakatan pemain.
Tambahan kepada keperJuan asas ini, kami meninjau isu-isu pennainan kad mental yang
berkaitan dengan fungsian permainan, keteguhan operasional dan kecekapan implementasi.
Pengkajian kami diberangsang oleh potensi pennainan berasaskan komputer dan rangkaian yang
melewati batas kemampuan kad fizikal, terutamanya pembongkaran maklumat terperinci kad
(seperti warna, darjat, simbol atau kebangsawanan) sambil merahsiakan nilai keseluruhan kad
tersebut.
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Mental card games are cryptographic protocols which permit verifiably fair gameplay among a
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priori distrustful and potentially untrustworthy remote parties and should minimally providewithout
the introduction of a trusted third party (TTP)---for card confidentiality, fraud detection
and conditional security against collusion. In addition to these basic requirements, we explore
into gameplay functionality, operational robustness and implementation efficiency issues of
mental card gaming. Our research is incited by the potential of computer-based and networkmediated
gameplay beyond the capability of physical cards, particularly fine-grained
information disclosure (such as colour, rank, symbol or courtliness) with preservation of card
secrecy. On the other hand, being network connected renders the protocol susceptible to
(accidental or intentional) disconnection attack, as well as other malicious behaviours
CALYPSO: Private Data Management for Decentralized Ledgers
Distributed ledgers provide high availability and integrity, making them a key enabler for practical and secure computation of distributed workloads among mutually distrustful parties. Many practical applications also require strong confidentiality, however. This work enhances permissioned and permissionless blockchains with the ability to manage confidential data without forfeiting availability or decentralization. The proposed Calypso architecture addresses two orthogonal challenges confronting modern distributed ledgers: (a) enabling the auditable management of secrets and (b) protecting distributed computations against arbitrage attacks when their results depend on the ordering and secrecy of inputs.
Calypso introduces on-chain secrets, a novel abstraction that enforces atomic deposition of an auditable trace whenever users access confidential data. Calypso provides user-controlled consent management that ensures revocation atomicity and accountable anonymity. To enable permissionless deployment, we introduce an incentive scheme and provide users with the option to select their preferred trustees. We evaluated our Calypso prototype with a confidential document-sharing application and a decentralized lottery. Our benchmarks show that transaction-processing latency increases linearly in terms of security (number of trustees) and is in the range of 0.2 to 8 seconds for 16 to 128 trustees
Recurring Contingent Service Payment
Fair exchange protocols let two mutually distrustful parties exchange digital
data in a way that neither party can cheat. They have various applications such
as the exchange of digital items, or the exchange of digital coins and digital
services between a buyer/client and seller/server.
In this work, we formally define and propose a generic blockchain-based
construction called "Recurring Contingent Service Payment" (RC-S-P). It (i)
lets a fair exchange of digital coins and verifiable service reoccur securely
between clients and a server while ensuring that the server is paid if and only
if it delivers a valid service, and (ii) ensures the parties' privacy is
preserved. RC-S-P supports arbitrary verifiable services, such as "Proofs of
Retrievability" (PoR) or verifiable computation and imposes low on-chain
overheads. Our formal treatment and construction, for the first time, consider
the setting where either client or server is malicious.
We also present a concrete efficient instantiation of RC- S-P when the
verifiable service is PoR. We implemented the concrete instantiation and
analysed its cost. When it deals with a 4-GB outsourced file, a verifier can
check a proof in only 90 milliseconds, and a dispute between a prover and
verifier is resolved in 0.1 milliseconds.
At CCS 2017, two blockchain-based protocols were proposed to support the fair
exchange of digital coins and a certain verifiable service; namely, PoR. In
this work, we show that these protocols (i) are susceptible to a free-riding
attack which enables a client to receive the service without paying the server,
and (ii) are not suitable for cases where parties' privacy matters, e.g., when
the server's proof status or buyer's file size must remain private from the
public. RC- S-P simultaneously mitigates the above attack and preserves the
parties' privacy
ARPA Whitepaper
We propose a secure computation solution for blockchain networks. The
correctness of computation is verifiable even under malicious majority
condition using information-theoretic Message Authentication Code (MAC), and
the privacy is preserved using Secret-Sharing. With state-of-the-art multiparty
computation protocol and a layer2 solution, our privacy-preserving computation
guarantees data security on blockchain, cryptographically, while reducing the
heavy-lifting computation job to a few nodes. This breakthrough has several
implications on the future of decentralized networks. First, secure computation
can be used to support Private Smart Contracts, where consensus is reached
without exposing the information in the public contract. Second, it enables
data to be shared and used in trustless network, without disclosing the raw
data during data-at-use, where data ownership and data usage is safely
separated. Last but not least, computation and verification processes are
separated, which can be perceived as computational sharding, this effectively
makes the transaction processing speed linear to the number of participating
nodes. Our objective is to deploy our secure computation network as an layer2
solution to any blockchain system. Smart Contracts\cite{smartcontract} will be
used as bridge to link the blockchain and computation networks. Additionally,
they will be used as verifier to ensure that outsourced computation is
completed correctly. In order to achieve this, we first develop a general MPC
network with advanced features, such as: 1) Secure Computation, 2) Off-chain
Computation, 3) Verifiable Computation, and 4)Support dApps' needs like
privacy-preserving data exchange
Multi-instance publicly verifiable time-lock puzzle and its applications
Time-lock puzzles are elegant protocols that enable a party to lock a message such that no one else can unlock it until a certain time elapses. Nevertheless, existing schemes are not suitable for the case where a server is given multiple instances of a puzzle scheme at once and it must unlock them at different points in time. If the schemes are naively used in this setting, then the server has to start solving all puzzles as soon as it receives them, that ultimately imposes significant computation cost and demands a high level of parallelisation. We put forth and formally define a primitive called “multi-instance time-lock puzzle” which allows composing a puzzle’s instances. We propose a candidate construction: “chained time-lock puzzle” (C-TLP). It allows the server, given instances’ composition, to solve puzzles sequentially, without having to run parallel computations on them. C-TLP makes black-box use of a standard time-lock puzzle scheme and is accompanied by a lightweight publicly verifiable algorithm. It is the first time-lock puzzle that offers a combination of the above features. We use C-TLP to build the first “outsourced proofs of retrievability” that can support real-time detection and fair payment while having lower overhead than the state of the art. As another application of C-TLP, we illustrate in certain cases, one can substitute a “verifiabledelay function” with C-TLP, to gain much better efficiency
Pisa: Arbitration outsourcing for state channels
State channels are a leading approach for improving the scalability of blockchains and cryptocurrencies. They allow a group of distrustful parties to optimistically execute an application-defined program amongst themselves, while the blockchain serves as a backstop in case of a dispute or abort. This effectively bypasses the congestion, fees and performance constraints of the underlying blockchain in the typical case. However, state channels introduce a new and undesirable assumption that a party must remain online and synchronised with the blockchain at all times to defend against execution fork attacks. An execution fork can revert a state channel's history, potentially causing financial damage to a party that is innocent except for having crashed. To provide security even to parties that may go offline for an extended period of time, we present Pisa, the first protocol to propose an accountable third party who can be hired by parties to cancel execution forks on their behalf. To evaluate Pisa, we provide a proof-of-concept implementation for a simplified Sprites and we demonstrate that it is cost-efficient to deploy on the Ethereum network
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