Mitra, Aritra2021-02-012021-02-012021-02-012021-01-20http://hdl.handle.net/10012/16784Since the advent of Bitcoin in 2008, the interest in blockchain technology has surged tremendously. Numerous applications have been proposed in the field of finance, healthcare, and supply chain over the last decade. And, as the popularity of blockchains continue to rise, blockchain platforms must be enhanced to support new application needs. We propose one such enhancement that is essential for financial applications and online marketplaces – support for time-based logic. Online marketplaces may need to validate transaction time-stamps against a perishable product’s expiry date to prevent sale of expired products. Similarly, financial applications in banking may also need a history of recent transactions for extending credit (like an overdraft) to a customer. As nodes in a blockchain operate in a distributed and trustless setting, it is imperative that they can access a global and trusted clock for verifying deadlines or examining a window of recent activity. In this thesis, we present a lightweight solution that assigns time-stamps to blocks at transaction validation time, which can be referenced as a global clock by all nodes in the network. Moreover, our solution also maintains a cache reflecting the effects of recent transactions. We implement our solution, called TimeFabric, in Hyperledger Fabric, a popular permissioned blockchain platform, and experimentally demonstrate high throughput and minimal overhead (approximately 3%) of maintaining trusted time. We also demonstrate a 2x performance improvement due to the cache, compared to retrieving transaction histories directly from the ledger.enpermissioned blockchain systemshyperledger fabricMaster Thesis