Adapting the TPL Trust Policy Language for a Self-Sovereign Identity World

Lukas Alber*, Stefan More*, Sebastian Mödersheim*, Anders Schlichtkrull*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference paperpeer-review


Trust policies enable the automated processing of trust decisions for electronic transactions.
We consider the Trust Policy Language TPL of the LIGHTest project that was designed for businesses and organizations to formulate their trust policies. Using TPL, organizations can decide if and how they want to rely on existing trust schemes like Europe's eIDAS or trust scheme translations endorsed by them. While the LIGHTest project is geared towards classical approaches like PKI-based trust infrastructures and X.509 certificates, novel concepts are on the rise: one example is the self-sovereign identity (SSI) model that enables users better control of their credentials, offers more privacy, and supports decentralized solutions. Since SSI is based on distributed ledger (DL) technology, it is a question how TPL can be adapted so that organizations can continue to enjoy the benefits of flexible policy descriptions with automated evaluation at a very high level of reliability.

Our contribution is a first step towards integrating SSI and the interaction with a DL into a Trust Policy Language. We discuss this on a more conceptual level and also show required TPL modifications. We demonstrate that we can make a integration of SSI concepts into TPL without changing syntax and semantics of TPL itself, and just have to add new formats and introduce a new built-in predicates for interacting with the DL. Another advantage of this is that the "business logic" aspect of a policy does not need to change, enable re-use of existing policies with the new trust model.
Original languageEnglish
Title of host publicationLecture Notes in Informatics
Subtitle of host publicationOpen Identity Summit 2021
Place of Publication Bonn
PublisherGesellschaft für Informatik
ISBN (Electronic)978-3-88579-706-7
Publication statusPublished - 30 Mar 2021
EventOpen Identity Summit 2021 - DTU Compute Lyngby, Lyngby, Denmark
Duration: 1 Jun 20212 Jun 2021


ConferenceOpen Identity Summit 2021
Abbreviated titleOID 2021
Internet address


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