3D Watermarking for Additive Manufacturing

Details

Supervisors

Macq, Benoît

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil électromécanicien, à finalité spécialisée: mécatronique

Abstract

enAdditive manufacturing, and Fused Deposition Modeling in particular, have become widely accessible, raising new concerns regarding intellectual property rights, authentication and traceability (particularly when a recovered printed object is part of a firearm that contains no information indicating who printed it). In this context, 3D watermarking allows traceability information to be encoded directly into the part at the time of manufacture. This Master’s thesis proposes an approach to watermarking in which a locally generated opaque identifier is embedded in the infill during slicing, within PrusaSlicer, and retrieved from a reconstructed density volume without access to the original model. Two encoding methods have been implemented: the first involves tilting the orientation of the infill layers, and the second involves tilting the lines of the infill grid. A third method, which uses a key-dependent hash to determine the encoded bit on the line, is explored but not implemented. Decoding was validated on cubes printed in PLA on a Prusa MK4S using a CT scanner simulation tool (TomoPy) in place of a physical scanner. These tests enabled the encoding and decoding methods to be optimised, and their capacity, robustness, fidelity and security to be assessed. The first method achieved a BER of 0% and a checksum pass rate of 100% across all tests conducted, but is limited in terms of capacity. Whilst the second method considerably increases this capacity, allowing for redundancy, it does so at the cost of a more fragile decoding chain. Ultimately, the results show that the payload can be encoded into the infill during slicing and decoded from a reconstructed volume without being detected by an average observer.