Organizations: Key Laboratory of Computing Power Network and Information Security, Ministry of Education, Shandong Computer Science Center, and Shandong Provincial Key Laboratory of Industrial Network and Information System Security, Shandong Fundamental Research Center for Computer Science, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China · Department of Computer Science, City University of Hong Kong (Dongguan), Dongguan, Guangdong 518057, China · School of Information Science and Engineering, Dalian Polytechnic University, Dalian 116034, China · School of Computer and Information Sciences, College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW 2308, Australia
Fixed image distortions do not cover an attacker that learns from paired clean and watermarked images. We study this paired-training threat with single-image inference: deployment uses neither the clean reference nor the watermark key, payload, or decoder. An encoder maps each image to a structural latent g and an auxiliary residual latent u. Push supervision reconstructs the watermarked image from D(gw,uw). Pull supervision trains the zero-auxiliary output D(Ag(gw;k),0) toward the paired clean image. At k=1.10,u=0, the four-method sweep gives an average BER of 0.3958, PSNR of 31.07 dB, and SSIM of 0.9554. Restoring u from 0 to 0.15 moves average BER from 0.3893 to 0.3357, while PSNR falls from 30.99 to 28.23 dB. The intervention supports decoder dependence on the auxiliary input in the evaluated setting. The accompanying theory is a conditional, post-hoc account of this behavior rather than an experimentally verified information-relocation result.
Figures & tables
Resource
Training and offline selection
Deployment on one image
Image input
Paired (xc,xw) examples
One watermarked image xw
Watermark families
Four represented families
The trained mapping can be applied to any input; results distinguish seen from excluded families
Clean reference
Used as the supervised target
Unavailable
Key, payload, or seed
Not required by the attack training loss
Unavailable
Decoder or detector
Used after training to report metrics and select (k,u)
Not queried or supplied to Aθ
Objective
Learn the paired clean target while retaining reconstruction fidelity
Produce one attacked image under the fixed selected setting
Table 1: Attacker capability by phase. Evaluator access is separated from the deployment inputs.
Figure 1: Paired push–pull training and single-image inference. Push reconstructs the watermarked input from (gw,uw) . Pull supervises the attacked zero-auxiliary output toward the paired clean target. Deployment follows xw→E→(gw,uw)→(Ag(gw;k),0)→xatk and does not use the clean reference or watermark verifier.
Figure 2: Pair-level supervision. The shared encoder maps aligned clean and watermarked images to two decoder inputs. The full watermarked path is pushed toward xw ; the attacked zero-auxiliary path is pulled toward xc .
Group
Representative terms
Function
Full-path push
∥D(gw,uw)−xw∥1
Preserve the watermarked input when both decoder inputs are present.
Structural pull
∥Ag(gw;k)−gc∥1
Align the attacked structural input with the paired clean representation.
Zero-auxiliary pull
∥D(Ag(gw;k),0)−xc∥1
Train the exact form of the deployed decoder input toward the paired clean target.
Reconstruction constraints
Clean reconstruction and ∥uc∥1
Retain visible content and discourage unnecessary clean residual storage.
Fidelity constraints
Perceptual, high-frequency, and edge losses
Penalize content, texture, and boundary changes in the attacked output.
Spectral constraints
Quantization and multiband magnitude losses
Regularize the attacked structural latent and its frequency profile.
Table 2: Functional groups in the training objective. The first three rows implement the paired push–pull structure; the remaining rows constrain fidelity and optimization.
Figure 3: Structural-latent frequency intervention. The rFFT coefficients are divided into radial bands, modified by the k -controlled operator, and returned to the decoder through an inverse rFFT.
k
u
BER →0.5
PSNR ↑
SSIM ↑
1.10
0.00
0.3958
31.07
0.9554
1.00
0.00
0.3938
31.07
0.9553
0.90
0.00
0.3867
31.11
0.9586
0.90
0.03
0.3720
31.30
0.9591
Table 3: Shared fine-sweep settings over DwtDct, DwtDctSvd, RivaGAN, and SSL Watermarking. Bold BER is closest to 0.5 ; bold PSNR/SSIM is larger.
u
BER →0.5
PSNR ↑
SSIM ↑
0.00
0.3893
30.99
0.9568
0.03
0.3695
31.05
0.9571
0.06
0.3521
30.83
0.9571
0.15
0.3357
28.23
0.9548
0.20
0.3426
26.09
0.9509
Table 4: Fine-sweep averages by auxiliary scale. Bold BER is closest to 0.5 ; bold PSNR/SSIM is larger.
Method
Family
BER/Acc Rem.
PSNR
SSIM
DwtDct
Unseen
0.4106
31.69
0.9656
DwtDctSvd
Seen
0.4856
31.54
0.9659
RivaGAN
Seen
0.3697
31.65
0.9597
SSL Watermarking
Unseen
0.3207
29.43
0.9303
StegaStamp
Seen
0.4251
31.37
0.9470
Stable Signature
Unseen
0.2275
28.35
0.8934
Table 5: Selected-point results on all methods. Tree-Ring reports Acc Removal; other rows report BER, with values closer to 0.5 preferred.
Attack
Mean RR ↑
Mean PSNR ↑
Mean SSIM ↑
Tree-Ring Acc Removal ↑
Tree-Ring PSNR ↑
Tree-Ring SSIM ↑
JPEG
0.1774
35.87
0.9669
0.0000
43.18
0.9923
Gaussian noise
0.4769
20.99
0.4947
0.0100
22.45
0.4555
CtrlRegen
0.9276
21.28
0.6139
0.2200
21.68
0.6570
WatermarkAttacker
0.8251
24.13
0.7049
0.1500
24.98
0.7702
SADRE-Cheng
0.7692
30.73
0.8792
0.0400
31.36
0.8812
Ours ( k=1.10,u=0 )
0.7464
30.67
0.9436
0.3200
26.81
0.8799
Table 6: Compact baseline comparison. Bit metrics average DwtDct, DwtDctSvd, RivaGAN, SSL Watermarking, StegaStamp, and Stable Signature. Tree-Ring detector results are not included in those averages.
Figure 4: Representative outputs, absolute residuals ∣xatk−xw∣×8 , and signed residuals (xatk−xw)×8 . Red and blue denote positive and negative signed changes. The full grid is in Appendix E .
Attack
Acc Removal ↑
PSNR ↑
SSIM ↑
No ring notch
0.3200
26.81
0.8799
r=0.40
0.3400
26.60
0.8723
r=0.45
0.3600
26.31
0.8727
r=0.50
0.3900
25.47
0.8724
r=0.55
0.3500
25.40
0.8739
r=0.60
0.3200
26.24
0.8770
Table 7: Tree-Ring ring-notch radius scan at k=1.10,u=0 .
Variant
Δ BER
Δ PSNR
w/o spectral alignment
−0.044
+1.19
w/o scheduled drop0 term
+0.038
−3.37
w/o perceptual constraint
+0.010
−0.31
w/o high-frequency residual
−0.001
−0.01
Fourier groups 4
+0.004
−0.06
Fourier groups 16
+0.001
−0.06
Table 8: Mean ablation changes over six bit-decoder methods. Tree-Ring is excluded. Positive Δ BER moves toward 0.5 because all values remain below 0.5 .
Appendix figures & tables15 assets
Supplementary material from the paper’s appendix.
Appendix
Setting
k
u
Avg. BER →0.5
PSNR ↑
SSIM ↑
Method BERs
K0U0
0.00
0.00
0.4042
22.51
0.9144
0.339/0.444/0.489/0.344
K1U0
1.00
0.00
0.3913
31.07
0.9553
0.316/0.414/0.470/0.365
K0U1
0.00
1.00
0.0697
37.80
0.9883
0.012/0.240/0.026/0.001
K1U1
1.00
1.00
0.1137
27.95
0.8583
0.125/0.225/0.105/0.000
Appendix
Table 9: Coarse-grid corners. Method BERs follow SSL Watermarking/DwtDct/DwtDctSvd/RivaGAN. Bold BER is closest to 0.5 ; bold PSNR/SSIM is larger.
Setting
k
u
Avg. BER →0.5
PSNR ↑
SSIM ↑
Method BERs
Attack optimum
1.10
0.00
0.3958
31.07
0.9554
0.324/0.418/0.479/0.362
Nearby point
1.00
0.00
0.3938
31.07
0.9553
0.324/0.411/0.473/0.368
Balanced point
0.90
0.00
0.3867
31.11
0.9586
0.319/0.418/0.463/0.348
Nonzero- u point
0.90
0.03
0.3720
31.30
0.9591
0.311/0.414/0.486/0.277
Higher- u point
0.90
0.05
0.3550
31.29
0.9593
0.312/0.413/0.475/0.219
Appendix
Table 10: Full set of selected fine-sweep points. Method BERs follow SSL Watermarking/DwtDct/DwtDctSvd/RivaGAN.
u
BER →0.5
Δ BER
PSNR ↑
Δ PSNR
SSIM ↑
0.00
0.3893
0.0000
30.99
0.00
0.9568
0.03
0.3695
−0.0198
31.05
+0.06
0.9571
0.05
0.3570
−0.0323
30.94
−0.05
0.9571
0.06
0.3521
−0.0372
30.83
−0.16
0.9571
0.10
0.3399
−0.0494
30.01
−0.98
0.9566
0.15
0.3357
−0.0536
28.23
−2.76
0.9548
Appendix
Table 11: Fine-sweep averages grouped by auxiliary scale. Deltas are relative to u=0 .
Setting
DwtDct
DwtDctSvd
RivaGAN
SSL Watermarking
BER →0.5
PSNR
SSIM
BER →0.5
PSNR
SSIM
BER →0.5
PSNR
SSIM
BER →0.5
PSNR
SSIM
k=1.10,u=0
0.4181
31.68
0.9656
0.4794
31.54
0.9659
0.3619
31.65
0.9597
0.3237
29.42
0.9302
k=0.90,u=0.03
0.4141
31.85
0.9683
0.4859
31.61
0.9685
0.2772
31.83
0.9627
0.3110
29.92
0.9368
Appendix
Table 12: Per-method fine-sweep metrics. Bold BER is closest to 0.5 ; bold PSNR/SSIM is larger.
Method
Selection
k
u
BER →0.5
PSNR ↑
SSIM ↑
DwtDct
Strongest attack
0.8500
0.2500
0.5003
25.47
0.9613
DwtDct
Best recovery
0.0000
1.0000
0.2403
37.27
0.9900
DwtDct
RR ≥0.50 best PSNR
0.9250
0.0375
0.4153
31.88
0.9679
DwtDctSvd
Strongest attack
0.5000
0.2500
0.5000
27.02
0.9661
DwtDctSvd
Best recovery
0.0000
1.0000
0.0262
37.59
0.9896
DwtDctSvd
RR ≥0.50 best PSNR
0.9400
0.0163
0.4675
31.67
0.9677
Appendix
Table 13: Per-method points recomputed from the scan result files. Strongest attack maximizes RR with PSNR ≥25 dB; constrained rows maximize PSNR subject to an RR floor.
Figure 5: Full PSNR (left) and BER (right) views across attack strength k and auxiliary scale u . BER should be read by proximity to 0.5 .
Attack
DwtDct
DwtDctSvd
RivaGAN
SSL Watermarking
StegaStamp
Stable Signature
Tree-Ring
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
Acc Rem.
PSNR
SSIM
Gaussian blur
0.3481
29.30
0.8906
0.0000
30.36
0.9050
0.0000
30.77
0.8945
0.0000
28.16
0.8413
0.0000
28.09
0.8482
0.1813
30.53
0.9062
0.0000
29.48
0.9003
Gaussian noise
0.6038
20.59
0.4996
0.3025
20.49
0.4762
0.0516
20.55
0.4794
0.5055
20.53
0.5135
0.0018
20.52
0.5072
0.1842
23.28
0.4925
0.0100
22.45
0.4555
JPEG
0.4038
33.67
0.9673
0.0156
34.28
0.9680
0.0025
34.42
0.9653
0.0255
34.43
0.9515
0.0001
34.63
0.9544
0.0848
43.80
0.9950
0.0000
43.18
0.9923
Brightness
0.4591
7.78
0.2871
0.3787
8.00
0.2931
0.1391
8.39
0.2910
0.0023
8.07
0.2538
0.0000
7.87
0.2584
0.3762
7.93
0.2425
0.0700
7.32
0.2448
Contrast
0.4587
14.21
0.6466
0.3787
14.35
0.6687
0.1309
14.39
0.6497
0.0048
14.34
0.5788
0.0000
14.00
0.5811
0.4279
14.69
0.5733
0.0100
13.91
0.5498
Appendix
Table 14: Conventional image-space attacks and our selected point. Bold BER is closest to 0.5 ; bold detector removal and fidelity metrics are larger.
Attack
DwtDct
DwtDctSvd
RivaGAN
SSL Watermarking
StegaStamp
Stable Signature
Tree-Ring
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
Acc Rem.
PSNR
SSIM
BM3D
0.4097
35.45
0.9422
0.3591
36.27
0.9412
0.0191
36.22
0.9391
0.2903
32.37
0.8715
0.0015
32.56
0.8837
0.2035
33.15
0.9019
0.0000
33.22
0.8973
CtrlRegen
0.4216
21.16
0.6242
0.4713
21.58
0.6455
0.4803
21.66
0.6272
0.5298
20.83
0.5594
0.4505
20.91
0.5949
0.5112
21.57
0.6320
0.2200
21.68
0.6570
WatermarkAttacker
0.4153
23.96
0.7154
0.4088
24.59
0.7357
0.4106
24.84
0.7210
0.4885
23.22
0.6439
0.2570
23.37
0.6755
0.5050
24.80
0.7378
0.1500
24.98
0.7702
SADRE-BMSHJ
0.4113
29.30
0.8676
0.4000
29.96
0.8760
0.3934
30.15
0.8615
0.5053
28.31
0.8115
0.3683
28.41
0.8272
0.3360
30.34
0.8679
0.0200
29.91
0.8587
SADRE-Cheng
0.4119
30.59
0.8943
0.3875
31.05
0.8968
0.4025
31.26
0.8851
0.4905
29.94
0.8503
0.3619
30.08
0.8629
0.2533
31.45
0.8861
0.0400
31.36
0.8812
Appendix
Table 15: Denoising, reconstruction, and regeneration attacks compared with our selected point. Bold BER is closest to 0.5 ; bold detector removal and fidelity metrics are larger.
Variant
DwtDct
DwtDctSvd
RivaGAN
SSL Watermarking
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
BER
PSNR
SSIM
Full
0.4106
31.69
0.9656
0.4856
31.54
0.9659
0.3697
31.65
0.9597
0.3208
29.43
0.9303
w/o spectral alignment
0.4131
32.89
0.9772
0.4550
33.01
0.9776
0.2828
32.89
0.9713
0.2717
30.30
0.9517
w/o scheduled drop0
0.4225
27.95
0.9440
0.4928
27.33
0.9425
0.4934
27.52
0.9322
0.3610
26.76
0.8976
w/o perceptual constraint
0.4144
31.35
0.9630
0.4684
31.18
0.9640
0.3159
31.11
0.9558
0.2995
30.00
0.9323
w/o high-frequency residual
0.4147
31.69
0.9656
0.4891
31.58
0.9657
0.3669
31.54
0.9581
0.3090
29.57
0.9303
Appendix
Table 16: Ablations on DwtDct, DwtDctSvd, RivaGAN, and SSL Watermarking at k=1.10,u=0 . Bold BER is closest to 0.5 ; bold PSNR/SSIM is larger.
Variant
StegaStamp
Stable Signature
Tree-Ring
BER
PSNR
SSIM
BER
PSNR
SSIM
Acc Rem.
PSNR
SSIM
Full
0.4251
31.37
0.9470
0.2275
28.35
0.8934
0.3200
26.81
0.8799
w/o spectral alignment
0.3573
33.28
0.9681
0.1975
28.78
0.9001
0.2700
27.54
0.8903
w/o scheduled drop0
0.4640
27.67
0.9175
0.2321
26.57
0.8825
0.1700
24.66
0.8410
w/o perceptual constraint
0.4164
31.04
0.9415
0.3863
27.48
0.8360
0.3700
25.08
0.8579
w/o high-frequency residual
0.4377
31.26
0.9453
0.2135
28.29
0.8922
0.3400
26.36
0.8756
Appendix
Table 17: Ablations on StegaStamp, Stable Signature, and Tree-Ring. Tree-Ring reports Acc Removal, not BER.
Figure 6: Full double residual comparison across all evaluated watermarking systems. Each watermarking block shows attack outputs, absolute residuals ∣xatk−xw∣×8 , and signed residuals (xatk−xw)×8 for the same attack methods as Tables 14 and 15 .
Stage
Operation
Output size
Notes
Input fusion
Concatenate RGB and H(rgb2gray(x))
4×H×W
High frequency extractor uses kernel 5 and σ=1.0 .
Head
Conv 4→64 , ResBlock (64)×2
64×H×W
First shared feature map.
Down 1
DownConv 64→128
128×H/2×W/2
The 64 channel head output is stored as a skip.
Down 2
DownConv 128→256
256×H/4×W/4
The 128 channel feature is stored as a skip.
Bridge
ResBlock (256)×4
256×H/4×W/4
Bottleneck refinement.
Up 1
UpConv 256→128 + skip
128×H/2×W/2
Additive skip from Down 2 input.
Appendix
Table 18: Encoder block table. A residual block is Conv (3,1,1) –ReLU–Conv (3,1,1) plus an identity skip. A down block is Conv (3,2,1) –Conv (3,1,1) –ReLU. An up block is bilinear upsample by 2, Conv (3,1,1) –Conv (3,1,1) –ReLU, followed by skip addition.
Stage
Operation
Output size
Notes
Input fusion
Concatenate g , u , and H(g)
18×H×W
C=16 , so 1+C+1=18 .
Projection
Conv 18→64
64×H×W
3×3 , stride 1, padding 1.
Residual trunk
ResBlock (64)×8
64×H×W
Full resolution residual refinement.
Expansion
Conv 64→256 , GELU
256×H×W
3×3 , stride 1, padding 1.
RGB head
Conv 256→3 , tanh
3×H×W
1×1 projection to RGB in [−1,1] .
Appendix
Table 19: Decoder block table. The decoder is full resolution throughout; it does not downsample.
Weight
Value
Active stage
Loss term / note
λinv
2.0
1–3
MSE between xc and D(gc,uc) .
λgrayc
1.0
1–3
Grayscale conformity for gc .
λrec1
1.0
1–3
Multiplies ∥D(gw,uw)−xw∥1 after the schedule scale srec1(e) .
λg−atk
3.0
2–3
∥Ag(gw;k)−gc∥1 ; zero in Stage 1.
λgray_hatw
1.0
1–3
Grayscale conformity for the attacked structural latent. In Stage 1, Ag is identity.
λdrop0
target 10.0
2–3
Same Stage 3 residual as Lrecov ; warms from 2.0 to 10.0 in Stage 2 and is 10.0 in Stage 3.
Appendix
Table 20: Complete loss weights used in the reported training schedule. Stage 1, Stage 2, and Stage 3 correspond to epochs 0–14, 15–79, and 80–139.
Stage
Epochs
Schedule
Stage 1
0–14
Ag is identity, attack strength k=0 , zero auxiliary attack losses are inactive, and srec1=1 .
Stage 2.1
15–35
Stage 2 starts. Attack strength follows a cosine ramp from 0.25 toward 0.75, λdrop0 warms from 2.0 toward 10.0, and srec1 begins cosine decay.
Stage 2.2
36–57
Middle third of Stage 2; same schedules continue. The pooled VGG Stage 2 scale is min(1,3ps2) and is saturated after the first third of Stage 2.
Stage 2.3
58–79
Final third of Stage 2. Attack strength reaches 0.75 and srec1 reaches its floor 0.2.
Stage 3
80–139
Full objective is active. Attack strength ramps continuously from 0.75 to 1.0 during the first 8 Stage 3 epochs and stays at 1.0 afterwards. Perceptual Stage 3 weights warm up over the first 5 Stage 3 epochs.
Appendix
Table 21: Stage transition and scheduled quantities.
Key Laboratory of Computing Power Network and Information Security, Ministry of Education; Shandong Computer Science Center; Shandong Provincial Key Laboratory of Industrial Network and Information System Security; and Shandong Fundamental Research Center for Computer Science, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, China · Department of Data Science, City University of Hong Kong, Hong Kong, China · School of Computer and Information Sciences, College of Engineering, Science and Environment, The University of Newcastle, Callaghan, NSW 2308, Australia +2
Faculty of Data Science, City University of Macau, Macao SAR, China · Corresponding Author · School of Information and Communications Engineering, Xi’an Jiaotong University, Xi’an 710049, China +2