Blind Watermarking for 3-D Printed Objects by Locally Modifying Layer Thickness

Abstract

We propose a new blind watermarking algorithm for three-dimensional (3D) printed objects that has applications in metadata embedding, robotic grasping, counterfeit prevention, and crime investigation. Our method can be used on fused deposition modeling (FDM) 3D printers and works by modifying the printed layer thickness on small patches of the surface of an object. These patches can be applied to multiple regions of the object, thereby making it resistant to various attacks such as cropping, local deformation, local surface degradation, or printing errors. The novelties of our method are the use of the thickness of printed layers as a one-dimensional carrier signal to embed data, the minimization of distortion by only modifying the layers locally, and one-shot detection using a common paper scanner. To correct encoding or decoding errors, our method combines multiple patches and uses a two-dimensional (2D) parity check to estimate the error probability of each bit to obtain a higher correction rate than a naive majority vote. The parity bits included in the patches have a double purpose because, in addition to error detection, they are also used to identify the orientation of the patches. In our experiments, we successfully embedded a watermark into flat surfaces of 3D objects with various filament colors using a standard FDM 3D printer, extracted it using a common 2D paper scanner and evaluated the sensitivity to surface degradation and signal amplitude.

Blind 3D-Printing Watermarking Using Moment Alignment and Surface Norm Distribution

“…Maia et al proposed Lay-erCode [37] that prints a 1D barcode across the object using dual-color printing, UV ink, or a layer thickness modification. We proposed a method [38] that embeds 2D tags by locally modifying the thickness of the printed layers.…”

A Voxel-Based Watermarking Scheme for Additive Manufacturing

“…Some researchers proposed to attach fingerprints on the surface of a model or to slightly alter the vertex coordinates or mesh connectivity of the model surface to prevent copyright violation [31][32][33][34]. Nonetheless, these protection mechanisms may be unintentionally damaged in the G-code generation, 3D printing, and post-processing stages.…”

“…As a result, the decoder may fail to accept the watermark in the verification process [4,5]. Hiding the watermark inside the model and printing it by using different materials, layer thickness, or filling patterns alleviate this problem [34,35]. Using the intrinsic characteristics of the 3D printer can offer some help too [36].…”

A Blind Watermarking Model of the 3D Object and the Polygonal Mesh Objects for Securing Copyright

“…Moreover, Ayubi et al in [12] presented a video watermarking method using 2D binary image. On the other hand, in [42,43], the proposed methods watermarked the 3D printed object, and in [18,[44][45][46], the presented methods were based on watermarking the 3D object using a different watermark sequence. e capacities are recorded by the number of bits per pixel (bpp) and the number of bits per vertex (bpv).…”