Major benefit of Digital Twins lies in collaboration across value added chains based on semantic interoperability. The concept of the Asset Administration Shell (AAS) enables sharing of semantically enriched information in Industrie 4.0 application scenarios and beyond. Nevertheless, a technical infrastructure is needed that can ensure data sovereignty, i.e. integrity, confidentiality and availability of information shared across business partners in value added chains. This paper presents the current state of work on such a technical infrastructure for Asset Administration Shells (AAS). It combines three technologies: a blockchain books who changed an AAS and when, a peer-to-peer (P2P) distributed file system encrypts and stores each version of an AAS and a version-control system tracks changes to an AAS in detail. An exemplary value added chain is defined, which will be implemented in a demonstrator. This demonstrator will be used to evaluate and improve the proposed technical infrastructure for collaboration of AAS across value added chains.