3rd place solution of ALASKA2 Image Steganalysis

Code for 3rd place solution of ALASKA2 Image Steganalysis on Kaggle.

A description of the method can be found in the following paper and this post in the kaggle discussion.

An Ensemble Model using CNNs on Different Domains for ALASKA2 Image Steganalysis
Kaizaburo Chubachi

Run Instructions

Environments

Run it on the docker image shown in env/Dockerfile.

(Optional) We mounted tmpfs in /tmp/ram because we used there to pass images read from the zip file to jpegio during training.

Data Preparation

# download data
mkdir -p data/input/
cd data/input/
kaggle competitions download alaska2-image-steganalysis
unzip alaska2-image-steganalysis.zip
cd ../../

# clone codes for some architectures
git clone https://github.com/facebookresearch/pycls
git clone https://github.com/iduta/pyconv

# extract metadata such as qualities of JPEG files.
python scripts/make_assets/make_quality_df.py
python scripts/make_assets/make_payload_stats.py

Reproduce the final submission

Run reproduce_final_submission.sh. We primarily used four NVIDIA Tesla V100 16GB to perform the training, so the script is written to use four GPUs.

Train 3-channel color image models

Make a configuration file like scripts/rgb_naive/rgb-4class-eb5-cutmix-p100.yaml. Put the file as scripts/rgb_naive/${CONFIG_NAME}.yaml. Then run following commands.

python scripts/rgb_naive/train.py \
    --config scripts/rgb_naive/${CONFIG_NAME}.yaml \
    --task download_model
python -m torch.distributed.launch --nproc_per_node=4 \
    scripts/rgb_naive/train.py \
    --resume \
    --config scripts/rgb_naive/${CONFIG_NAME}.yaml \
    --task train

Train a DCT coefficient model

Make a configuration file like scripts/dct_d8/dct-d8-stride-1-2-l16-q-cos.yaml. Put the file as scripts/dct_d8/${CONFIG_NAME}.yaml. Then run following commands.

python scripts/dct_d8/train.py \
    --config scripts/dct_d8/${CONFIG_NAME}.yaml \
    --task download_model
python -m torch.distributed.launch --nproc_per_node=4 \
    scripts/dct_d8/train.py \
    --resume \
    --config scripts/dct_d8/${CONFIG_NAME}.yaml \
    --task train

Train a MLP

Before training, dump feature maps of trained CNNs.

python -m torch.distributed.launch --nproc_per_node=4 \
    scripts/rgb_naive/train.py \
    --config scripts/rgb_naive/${CONFIG_NAME}.yaml \
    --task predict_feature

Make a configuration file like scripts/cnn_feature_concat/dct-d8-stride-1-2-l16-q-cos.yaml, and put the file as scripts/dct_d8/${CONFIG_NAME}.yaml. Then run following commands.

python scripts/cnn_feature_concat/train.py \
    --config scripts/cnn_feature_concat/${CONFIG_NAME}.yaml \
    --task train

Citation

@inproceedings{chubachi2020alaska,
  author={Kaizaburo Chubachi},
  booktitle={2020 IEEE International Workshop on Information Forensics and Security (WIFS)}, 
  title={An Ensemble Model using CNNs on Different Domains for ALASKA2 Image Steganalysis}, 
  year={2020},
  pages={1-6},
  doi={10.1109/WIFS49906.2020.9360892}
}