Binding of endpoints to identifiers by on-chain proofs

In many applications, identity management (IdM) is used to associate a subject public key with an endpoint at which the subject can be contacted (telephone number, email, etc.). In decentralized applications based on blockchains, it is desirable for the IdM to be decentralized as well. In certain applications, it is paramount to be certain that an endpoint actually belong to a specific subject. Currently, when this is needed, endpoints are either verified by who needs it, which is impractical in blockchain-based applications, or by a centralized authority, which contrasts with the spirit of the blockchain.In this paper, we show two layer-two blockchain-based protocols to prove the association between a subject and an endpoint in a decentralized manner. Our protocols are compatible with a wide variety of endpoints and contribute to fill the gap of the current self sovereign IdM approaches with respect to decentralization. We analyze the security of our proposals and evaluate performances and costs against the common approaches.