Digital credentials management system using rejectable soulbound tokens

Digital credentials are being issued by authorized entities to facilitate the digital identification of their users. Blockchain offers some inherent features that are highly advantageous for the management of credentials. Non-fungible tokens, or NFTs, might seem to be a perfect fit for the implementation of digital credentials. However, some crucial requirements for credentials are the non-transferability of the credential and that the authorized entity should receive explicit acceptance from the user who will own the new credential, which are features lacking in the current NFTs. This paper introduces a management system focused on issuing digital access credentials, enhancing traditional features by enabling the association of terms and conditions (T &C) during issuance and providing users with non-repudiation of reception evidence upon acceptance. Leveraging an enhanced version of the soulbound tokens (SBTs), called RejSBTs, introduced in our previous work, the new system guarantees non-repudiation of reception and origin proofs. Furthermore, we provide a detailed implementation of the system, including solidity smart contracts, accompanied by a comprehensive cost and security analysis.