The contract concerns the project „pac4j“ which covers the development of credential verification for the European Digital Identity Wallet in pac4j, an open source Java library that checks who users are and what they may access in web applications. As part of four consecutive milestones, the contract covers the reworking of pac4j for a new major version, with a review of every module and of its fifteen framework integrations; the development of the trust mechanisms through which organisations recognise each other without prior registration, beyond their current basic form; the expansion of wallet credential verification to new ways for services to identify themselves and to tie a credential to one approved transaction, examined empirically against several wallets; and the validation of the resulting implementations against the conformance tests of the OpenID Foundation. The aim of this service is to give public bodies and smaller organisations across Europe a secure, independently validated, and openly licensed way to accept the European Digital Identity Wallet, and to reduce the security risk carried by a library downloaded about one million times per month.