  In a global economy with many competitive participants, licensing and
tracking of 3D printed parts is desirable if not mandatory for many use-cases.
We investigate a blockchain-based approach, as blockchains provide many
attractive features, like decentralized architecture and high security
assurances. An often neglected aspect of the product life-cycle management is
the confidentiality of transactions to hide valuable business information from
competitors. To solve the combined problem of trust and confidentiality, we
present a confidential licensing and tracking system which works on any
publicly verifiable, token-based blockchain that supports tokens of different
types representing licenses or attributes of parts. Together with the secure
integration of a unique eID in each part, our system provides an efficient,
immutable and authenticated transaction log scalable to thousands of
transactions per second. With our confidential Token-Based License Management
system (cTLM), large industries such as automotive or aviation can license and
trace all parts confidentially.
