Abstracts

The thesis investigates how a blockchain can be used to build a decentralised public key infrastructure for the web, by proposing a custom federation blockchain relying on honest majority. Our main contribution is the design of a Proof of Stake protocol based on a stake tree, which builds upon an idea called follow-the-satoshi used in previous papers. Digital identities are stored in an authenticated self-balancing tree maintained by blockchain nodes. Our back-of-the-envelope calculations, based on the size of the domain name system, show that the block size must be set to at least 5.2 MB, while each blockchain node with a one-month transaction history would need to store about 243 GB. Thin clients would have to synchronise about 13.6 MB of block headers per year, and download an additional 3.7 KB of proof data for every leaf certificate which is to be checked. Uppsatsen undersker hur en blockkedja kan anvndas fr att bygga en decentraliserad publik nyckel-infrastruktur fr webben. Vi ger ett designfrslag p en blockkedja som drivs av en plitlig grupp av noder, dr en majoritet antas vara rliga. Vrt huvudsakliga bidrag r utformningen av ett Proof of Stake-protokoll baserat p ett staketrd, vilket bygger p en id som kallas follow-the-satoshi omnmnd i tidigare publikationer. Digitala identiteter sparas i ett autentiserat, sjlvbalanserande trd som underhlls av noder anslutna till blockkedjentverket. Vra preliminra berkningar baserade p storleken av DNS-systemet visar att blockstorleken mste sttas till tminstone 5.2 MB, medan varje nod med en mnads transaktionshistorik mste spara ungefr 243 GB. Webblsare och andra resurssnla klienter mste synkronisera 13.6 MB data per r, och ladda ner ytterligare 3.7 KB fr varje anvndarcertifikat som skall valideras.