Chainspace: A Sharded Smart Contracts Platform

Abstract

Chainspace is a decentralized infrastructure, known as a distributed ledger, that supports user defined smart contracts and executes user-supplied transactions on their objects. The correct execution of smart contract transactions is verifiable by all. The system is scalable, by sharding state and the execution of transactions, and using S-BAC, a distributed commit protocol, to guarantee consistency. Chainspace is secure against subsets of nodes trying to compromise its integrity or availability properties through Byzantine Fault Tolerance (BFT), and extremely highauditability, non-repudiation and 'blockchain' techniques. Even when BFT fails, auditing mechanisms are in place to trace malicious participants. We present the design, rationale, and details of Chainspace; we argue through evaluating an implementation of the system about its scaling and other features; we illustrate a number of privacy-friendly smart contracts for smart metering, polling and banking and measure their performance.

Scalable and Privacy-Preserving Design of On/Off-Chain Smart Contracts

“…As can be seen, in this example, the onchain contract consists of four light/public functions and two extra functions while the off-chain contract consists of one heavy/private function and one extra function. Here we note that the parameters, constructor and modifiers (e.g., beforeT1, certifiedparticipantOnly) are omitted in Algorithm 2. a n c e [ p a r t i c i p a n t [ 0 ] ] = 0 ; a c c o u n t B a l a n c e [ p a r t i c i p a n t [ 1 ] ] = 0 ; i f ( w i n n e r == t r u e ) { p a r t i c i p a n t [ 1 ] . t r a n s f e r ( a c c o u n t B a l a n c e [ p a r t i c i p a n t [ 0 ] ] + a c c o u n t B a l a n c e [ p a r t i c i p a n t [ 1 ] ] ) ; } e l s e { p a r t i c i p a n t [ 0 ] .…”

“…Thus, the proposed approach is a plug-and-play solution that is compatible with existing smart contract systems and their time-tested infrastructure and community. In addition, the combination of the proposed approach and other system-level or application-level solutions, such as sharding [1] and zero knowledge proof [6], can further enhance the scalability and privacy of the smart contract systems.…”

AStERISK: Auction-based Shared Economy ResolutIon Markets for Blockchain Platforms

“…We provide an open-source implementation 4 of the AStERISK smart contract presented in Section IV-A for Chainspace [25]. Our implementation does not enforce conditions on timers t commit and t reveal as Chainspace currently does not provide functions to check block heights.…”

“…Weak synchrony[24] is required by many smart contract platforms[25],[26], and by distributed key generation protocols required by Coconut[22] 2. The tumbler application is described at Section V.A of Coconut[22].…”

YODA: Enabling computationally intensive contracts on blockchains with Byzantine and Selfish nodes

“…Moreover, they require on-chain computation of a part of a CIC to determine its correct solution in some cases. Note that off-chain CIC computation is not the same as achieving consensus about blocks using shards [2], [10], [14], [15], [31]. Blocks can in general take many valid values and are computationally easy to verify unlike CIC solutions which have only one correct value and are expensive to verify.…”