Bringing Decentralized Search to Decentralized Services

This paper addresses a key missing piece in the current ecosystem of decentralized services and blockchain apps: the lack of decentralized, verifiable, and private search. Existing decentralized systems like Steemit, OpenBazaar, and the growing number of blockchain apps provide alternatives to existing services. And yet, they continue to rely on centralized search engines and indexers to help users access the content they seek and navigate the apps. Such centralized engines are in a perfect position to censor content and violate users’ privacy, undermining some of the key tenets behind decentralization. To remedy this, we introduce DESEARCH, the first decentralized search engine that guarantees the integrity and privacy of search results for decentralized services and blockchain apps. DESEARCH uses trusted hardware to build a network of workers that execute a pipeline of small search engine tasks (crawl, index, aggregate, rank, query). DESEARCH then introduces a witness mechanism to make sure the completed tasks can be reused across different pipelines, and to make the final search results verifiable by end users. We implement DESEARCH for two existing decentralized services that handle over 80 million records and 240 GBs of data, and show that DESEARCH can scale horizontally with the number of workers and can process 128 million search queries per day.