Organizations nowadays are largely computerized, with a mixture of internal and external services providing them with on-demand functionality. In some situations (e.g. emergency situations), cross-organizational collaboration is needed, providing external users access to internal services. Trust between partners in such a collaboration can however be an issue. Although (federated) access control policies may be in place, it is unclear which data was requested and delivered after a collaboration has finished. This may lead to disputes between participating organizations. The open-source permissioned blockchain Hyperledger Fabric is utilized to create a logging mechanism for the actions performed by the participants in such a collaboration. T...