US 12,174,923 B1
Zero-watermarking method and device for BIM data, and medium
Xingxiang Jiang, Changsha (CN); Qianwen Zhou, Huaian (CN); Changqing Zhu, Nanjing (CN); Hua Sun, Changsha (CN); Luanyun Hu, Changsha (CN); Sheng Chen, Changsha (CN); Xi Liu, Changsha (CN); Tan Chen, Changsha (CN); Yujing Liu, Shaoyang (CN); and Na Ren, Nanjing (CN)
Assigned to The Third Surveying and Mapping Institute of Hunan Province, Changsha (CN); and Nanjing Normal University, Nanjing (CN)
Filed by The Third Surveying and Mapping Institute of Hunan Province, Changsha (CN); and Nanjing Normal University, Nanjing (CN)
Filed on Jun. 4, 2024, as Appl. No. 18/732,644.
Claims priority of application No. 202311445493.5 (CN), filed on Nov. 2, 2023.
Int. Cl. G06F 21/16 (2013.01); G06F 21/60 (2013.01)
CPC G06F 21/16 (2013.01) [G06F 21/602 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A zero-watermarking method for building information modeling (BIM) data, comprising:
screening, based on a secret key Key, primitives of a model with original BIM data to obtain primitives of a target type, and adding the primitives of the target type to a set E; calculating a coordinate Vi(xi, yi, zi), i∈[1, N] of a center point of each of the primitives of the target type, wherein N represents a length of the set E; and taking an average value of coordinates of the primitives of the target type as a coordinate Vc(xc, yc, zc) of a center point of the model;
sorting Z values of the primitives of the target type in the set E to obtain a sorted Z value set [Zmin, Zmax];
in response to Zmax<2×Zmax−1 and Zmin>2×Zmin+1, determining the sorted Z value set [Zmin, Zmax] as a target Z value set [Zmin, Zmax];
in response to Zmax>2×Zmax−1 or Zmin<2×Zmin+1, obtaining, based on the sorted Z value set [Zmin, Zmax], the target Z value set [Zmin Zmax] through performing the following steps at least once until the target Z value set [Zmin, Zmax] satisfies Zmax<2×Zmax−1 and Zmin>2×Zmin+1: for the sorted Z value set [Zmin, Zmax], in a situation of Zmax>2×Zmax−1, deleting Zmax from the sorted Z value set [Zmin, Zmax]; and in a situation of Zmin<2×Zmin+1, deleting Zmin from the sorted Z value set [Zmin, Zmax], to thereby obtain a next Z value set [Zmin, Zmax] as the sorted Z value set [Zmin, Zmax];
calculating, based on a length n of an original watermarking sequence, a step length ΔZ by using a formula (3), wherein the formula (3) is expressed as follows:

OG Complex Work Unit Math
wherein Zmax represents a maximum value of the target Z value set [Zmin, Zmax], which is considered as a maximum Z value of the primitives of the target type in the set E, and Zmin represents a minimum value of the target Z value set [Zmin, Zmax], which is considered as a minimum Z value of the primitives of the target type in the set E;
dividing, according to the step length ΔZ, the primitives of the target type in the set E into n clusters to obtain n primitive clusters, wherein Z coordinates of primitives of the target type in each primitive cluster satisfy the following formula (4):

OG Complex Work Unit Math
wherein k represents a number of primitives of the target type in a jth primitive cluster Cj, and Ei represents an ith primitive of the target type in the primitive cluster Cj;
calculating a norm ρi of each primitive of the target type in the primitive cluster Cj to the center point Vc of the model to calculate norm skewness measurement, and constructing, based on positivity and negativity of the norm skewness measurement, watermarking information Wj by using a formula (5) to thereby obtain a watermarking sequence W, wherein the formula (5) is expressed as follows:

OG Complex Work Unit Math
wherein αj represents the norm skewness measurement of the primitive cluster Cj, when the norm skewness measurement αj is 0, indicating that norms of the primitives of the target type in the primitive clusters are symmetrical; and the watermarking information Wj is set as 1; and
performing, based on a formula (6), an exclusive or (XOR) operation on the watermarking sequence W and a scrambled original watermarking sequence W0 to obtain a zero-watermarking binary sequence W′; wherein the formula (6) is expressed as follows:
W′=W⊕W0  (6);
wherein ⊕ represents the XOR operation.