Nowadays, there are a plethora of services that are provided and paid for online, such as
video streaming subscriptions, car-share, vehicle parking, purchasing tickets for events, etc. Online
services usually issue tokens that are directly related to the identities of their users after they sign
up to a platform; users need to authenticate themselves by using the same credentials each time
they use the service. Likewise, when using in-person services, such as going to a concert, after
paying ...
Nowadays, there are a plethora of services that are provided and paid for online, such as
video streaming subscriptions, car-share, vehicle parking, purchasing tickets for events, etc. Online
services usually issue tokens that are directly related to the identities of their users after they sign
up to a platform; users need to authenticate themselves by using the same credentials each time
they use the service. Likewise, when using in-person services, such as going to a concert, after
paying for this service, the user usually receives a ticket, which proves that he/she has the right to
use that service. In both scenarios, the main concerns surround the centralization of these systems
and that they do not ensure customers’ privacy. The involved service providers are trusted third
parties—authorities that offer services and handle private data about users. In this paper, we designed
and implemented FORT, a decentralized system that allows customers to prove their rights to use
specific services (either online or in-person) without revealing sensitive information. To achieve
decentralization, we proposed a solution where all of the data are handled by a blockchain. We
describe and uniquely identify users’ rights using non-fungible tokens (NFTs), and possession of
these rights is demonstrated by using zero-knowledge proofs—cryptographic primitives that allow
us to guarantee customers’ privacy. Furthermore, we provide benchmarks of FORT, which show
that our protocol is efficient enough to be used in devices with low computing resources, such as
smartphones or smartwatches, which are devices commonly used in our use case scenario
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