# A Fragile Watermarking Scheme for Authenticity Verification of 3D Models in GLB Format
## 1 Introduction  
The advent of technology has given rise to novel methods and media for transmitting data, including various three-dimensional (3D) models. The utilisation of 3D models has become pervasive in the domain of electronic entertainment, encompassing areas such as gaming, animation, virtual reality (VR), augmented reality (AR), and the internet of things (IoT). In this sector, numerous enterprises offer remote work opportunities. For instance, a graphic designer prepares a model, which is sent to a programmer, who implements the object in the virtual world. Furthermore, the range of applications for 3D models is expanding at an accelerating rate. Thanks to 3D scanning technology, medical data [1], cultural monuments [2], measurement results [3] and crime scenes [4] can be captured as 3D models. Data protection continues to be a top priority, as evidenced by the rapidly increasing number of online frauds and rising digital crime [5, 6]. While cryptographic techniques offer a solution, they can limit data access or necessitate the storage and transmissionof an additional electronic signature file alongside the data. Steganographic techniques, which involve attaching additional hidden information directly to the data, are devoid of these drawbacks. Steganographic techniques that allow data to be hidden in sound [7], images [8], video [9] and 3D models are popular. The media in which data is hidden are called covers, and there is dedicated research concerning the creation of covers that can hide large amounts of data [10]. In addition, steganographic techniques allow for the attachment of robust watermarks [11] and also for fragile watermarking [12]. There is also a branch of research focused on reversible watermarking. The term reversible refers to the ability to embed and later extract a watermark or other data without permanently modifying the asset [13; 14]. The implementation of a fragile watermark necessitates that even the most minuscule alteration to the model will result in the act of tampering. This mechanism is highly effective for authentication, as any damage to the watermark definitively indicates data modification. In the field of watermarking, fragile watermarking is a niche issue--the majority of existing methods focus on robust watermarking [15; 16; 17; 18]. Among the methods for the fragile watermarking of 3D models, virtually all place the watermark in the coordinates of the vertex positions [19; 20] and operate on standard formats such as ply, obj or fbx. To date, no publications have addressed the implementation of model watermarking in the glb file, which is a binary version of the graphics library transmission format (gITF). The gITF standard facilitates the storage of sophisticated three-dimensional scenes comprising multiple models and information such as light sources, camera settings, animations, and transformation matrices. The motivation for writing this article was the desire to explore the issue of watermarking for glb files and the possibility of embedding the watermark in vertex attributes other than position. The use of normal vectors, texture coordinates, or other vertex attributes to embed a watermark represents an unexplored domain that exhibits considerable potential in the context of steganographic applications. The authors also wanted to propose a method suitable for low-cost devices such as VR, AR, and IoT. The primary objective of this paper is to present a watermarking method for 3D models stored in files with the glb extension. The method is designed to introduce minimal distortion while simultaneously ensuring the concealment of the introduced modifications. Additionally, it is intended to enable the detection of even a single bit alteration within the model. Furthermore, a series of tests were conducted to ascertain the relationship between the number of introduced changes in various vertex attributes (position, texture coordinates, normal vectors) and the level of model distortion and transparency.