HiDDeN

Pytorch implementation of paper "HiDDeN: Hiding Data With Deep Networks" by Jiren Zhu*, Russell Kaplan*, Justin Johnson, and Li Fei-Fei: https://arxiv.org/abs/1807.09937
*: These authors contributed equally

The authors have Lua+Torch implementation here: https://github.com/jirenz/HiDDeN

Note that this is a work in progress, and I was not yet able to fully reproduce the results of the original paper.

Requirements

You need Pytorch 1.0 with TorchVision to run this. If you want to use Tensorboard, you need to install TensorboardX and Tensorboard. This allows to use a subset of Tensorboard functionality to visualize the training. However, this is optional. The code has been tested with Python 3.6+ and runs both on Ubuntu 16.04, 18.04 and Windows 10.

Data

We use 10,000 images for training and 1,000 images for validation. Following the original paper, we chose those 10,000 + 1,000 images randomly from one of the coco datasets. http://cocodataset.org/#download

The data directory has the following structure:

<data_root>/
  train/
    train_class/
      train_image1.jpg
      train_image2.jpg
      ...
  val/
    val_class/
      val_image1.jpg
      val_image2.jpg
      ...

train_class and val_class folders are so that we can use the standard torchvision data loaders without change.

Running

You will need to install the requirements, then run

python main.py new --name <experiment_name> --data-dir <data_root> --batch-size <b> 

By default, tensorboard logging is disabled. To enable it, use the --tensorboard switch. If you want to continue from a training run, use

python main.py continue --folder <incomplete_run_folder>

There are additional parameters for main.py. Use

python main.py --help

to see the description of all of the parameters. Each run creates a folder in ./runs/<experiment_name date-and-time> and stores all the information about the run in there.

Running with Noise Layers

You can specify noise layers configuration. To do so, use the --noise switch, following by configuration of noise layer or layers. For instance, the command

python main.py new --name 'combined-noise' --data-dir /data/ --batch-size 12 --noise  'crop((0.2,0.3),(0.4,0.5))+cropout((0
.11,0.22),(0.33,0.44))+dropout(0.2,0.3)+jpeg()'

runs the training with the following noise layers applied to each watermarked image: crop, then cropout, then dropout, then jpeg compression. The parameters of the layers are explained below. It is important to use the quotes around the noise configuration. Also, avoid redundant spaces If you want to stack several noise layers, specify them using + in the noise configuration, as shown in the example.

Update 16.04.2019 Prior to this, the noise layers in our implementation worked sequentially, that is, resize(...)+jpeg() first resized the image and then applied jpeg compression. This is different from the behaviour described in the paper. From 16.04.2019, this has been changed. Now, if several noise layers are specified, one of them is picked at random and applied to the batch.

Noise Layer paremeters

• Crop((height_min,height_max),(width_min,width_max)), where (height_min,height_max) is a range from which we draw a random number and keep that fraction of the height of the original image. (width_min,width_max) controls the same for the width of the image. Put it another way, given an image with dimensions H x W, the Crop() will randomly crop this into dimensions H' x W', where H'/H is in the range (height_min,height_max), and W'/W is in the range (width_min,width_max). In the paper, the authors use a single parameter p which shows the ratio (H' * W')/ (H * W), i.e., which fraction of the are to keep. In our setting, you can obtain the appropriate p by picking height_min, height_max width_min, width_max to be all equal to sqrt(p)
• Cropout((height_min,height_max), (width_min,width_max)), the parameters have the same meaning as in case of Crop.
• Dropout(keep_min, keep_max) : where the ratio of the pixels to keep from the watermarked image, keep_ratio, is drawn uniformly from the range (keep_min,keep_max).
• Resize(keep_min, keep_max), where the resize ratio is drawn uniformly from the range (keep_min, keep_max). This ratio applies to both dimensions. For instance, of we have Resize(0.7, 0.9), and we randomly draw the number 0.8 for a particular image, then the resulting image will have the dimensions (H * 0.8, W * 0.8).
• Jpeg does not have any parameters.

Experiments

The data for some of the experiments are stored in './experiments/ folder. This includes: figures, detailed training and validation losses, all the settings in pickle format, and the checkpoint file of the trained model. Here, we provide summary of the experiments.

Setup

We try to follow the experimental setup of the original paper as closely as possibly. We train the network on 10,000 random images from COCO dataset. We use 200-400 epochs for training and validation. The validation is on 1,000 images. During training, we take randomly positioned center crops of the images. This makes sure that there is very low chance the network will see the exact same cropped image during training. For validation, we take center crops which are not random, therefore we can exactly compare metrics from one epoch to another.

Due to random cropping, we observed no overfitting, and our train and validation metrics (mean square error, binary cross-entropy) were extremely close. For this reason, we only show the validation metrics here.

When measuring the decoder accuracy, we do not use error-correcting codes like in the paper. We take the decoder output, clip it to range [0, 1], then round it up. We call this "Decoder bitwise error". We also report mean squate error of of the decoder for consistency with the paper.

Experimental runs

This table summarizes experimental runs. Detailed information about the runs can be found in ./experiments folder.

experiment_name	loss	encoder_mse	bitwise-error	dec_mse	epoch
crop(0.2-0.25)	0.046	0.0019	0.0603	0.0435	300
cropout(0.55-0.6)	0.071	0.0011	0.0647	0.0662	300
dropout(0.55-0.6)	0.033	0.0019	0.008	0.0298	300
jpeg	0.0272	0.0025	0.0096	0.0253	300
resize(0.7-0.8)	0.0251	0.0016	0.0052	0.0238	300
combined-noise	0.1681	0.0028	0.2109	0.1648	400

• No noise means no noise layers.
• Crop((0.2,0.25),...) is shorthand for Crop((0.2,0.25),(0.2,0.25)). This means that the height and the weight of the cropped image have the expected value of (0.25 + 0.2)/2 = 0.225. Therefore, the ratio of (expected) area of the Cropped image against the original image is 0.225x0.225 ≈ 0.05. The paper used p = 0.035.
• Cropout((0.55,0.6),...) is a shorhand for Cropout((0.55,0.6),(0.55,0.6)). Similar to Crop(...), this translates to ratio of Cropped vs original image areas with p ≈ 0.33. The paper used p = 0.3
• Jpeg the same as the Jpeg layer from the paper. It is a differentiable approximation of Jpeg compression with the highest compression coefficient.
• combined-noise is the configuration 'crop((0.4,0.55),(0.4,0.55))+cropout((0.25,0.35),(0.25,0.35))+dropout(0.25,0.35)+resize(0.4,0.6)+jpeg()'. This is somewhat similar to combined noise configuation in the paper.