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ImageCLEF 2019 Security - Stego image discovery

Identify stego images



Note: ImageCLEF Security 2019 is divided into 3 subtasks (challenges):

  • Task 1: Forged File Discovery

  • Task 2: Stego Image Discovery

  • Task 3: Secret Message Discovery

This challenge is about Stego Image Discovery(task 2). For information on the Forged File Discovery(task 1) challenge click here . For information on the Secret Message Discovery(task 3) challenge click here . All of these challenges share similar scenario. Registering for one of these challenges will automatically give you access to the other ones.

Note: Do not forget to read the Rules section on this page.


File Forgery Detection (FFD) is a serious problem concerning digital forensics examiners. Fraud or counterfeits are common causes for altering files. Another example is a child predator who hides porn images by altering the image extension and in some cases by changing the image signature. Many proposals have been made to solve this problem and the most promising ones concentrate on the image content. It is also common that anyone who wants to hide any kind of information in plain sight without being perceived to use steganography. Steganography is the practice of concealing a file, message, image or video within another file, message, image, or video. The word steganography combines the Greek words steganos (στεγανός), meaning “covered” and graphein (γράφειν) meaning “writing”. The most usual cover medium for hiding data are images.

Challenge description

You are a professional digital forensic examiner collaborating with the police, who suspects that there is an ongoing fraud in the Central Bank. After obtaining a court order, police gain access to a suspect’s computer in the bank with the purpose to look for images proving the suspect guilty. However, police suspects that he has managed to change extension and signature of some images, so that they look like pdf files. Additionally, it is highly probable that the suspect has used steganography software to hide messages within some images that could reveal valuable information of his collaborators.

The goal of this challenge is to examine if an image could hide a text message. Identify the altered images that hide steganographic content.


Training set for stego image discovery (i.e. task 2 ) consists of 1000 images of jpg format. 500 of these images are clean while the rest are stego.

Submission instructions

As soon as the submission is open, you will find a “Create Submission” button on this page (just next to the tabs)

Please note that each group is allowed for maximum of 10 runs per task.

** Identify Stego Images**

For the submission of the task we expect the following format:

<Figure-ID>;<yes/no> —> Figure-ID>;<1/0>


1741_02;1 if the image includes stego

1742_02;0 if the image does NOT include stego

1743_02;1 if the image includes stego

You need to respect the following constraints:

  • The separator between the figure ID and the description has to be be a semicolon (;).

  • The file to upload must be a .txt file.

  • Each figure ID of the test set must be included in the runfile exactly once.

  • The result cannot be specified more than once for the same figure ID.


Information will be posted after the challenge ends.


For assessing performance, classic metrics are used: Precision, Recall and F1.

Precision In pattern recognition, information retrieval and binary classification, precision is the fraction of relevant instances among the retrieved instances. Precision could be defined as the fraction of actual detected images with hidden messages among all the detected images with hidden a message:

Precision= nº of actual detected images with hidden messages /Total detections of altered images with hidden messages

Recall In pattern recognition, information retrieval and binary classification, recall is the fraction of relevant instances that have been retrieved over the total amount of relevant instances. Recall could be defined as the fraction of actual detected images with hidden messages among all the images with hidden a message:

Recall = nº of actual detected images with hidden messages /Total altered images with hidden messages

F-measure F-measure is the harmonic mean of precision and recall, mathematically expressed as

F_1=2∙(Precision ∙ Recall)/(Precision + Recall )


Note: In order to participate in this challenge you have to agree on the terms & conditions You will find more information on the ‘Dataset’ tab.

ImageCLEF lab is part of the Conference and Labs of the Evaluation Forum: CLEF 2019. CLEF 2019 consists of independent peer-reviewed workshops on a broad range of challenges in the fields of multilingual and multimodal information access evaluation, and a set of benchmarking activities carried in various labs designed to test different aspects of mono and cross-language Information retrieval systems. More details about the conference can be found here .

Submitting a working note with the full description of the methods used in each run is mandatory. Any run that could not be reproduced thanks to its description in the working notes might be removed from the official publication of the results. Working notes are published within CEUR-WS proceedings, resulting in an assignment of an individual DOI (URN) and an indexing by many bibliography systems including DBLP. According to the CEUR-WS policies, a light review of the working notes will be conducted by ImageCLEF organizing committee to ensure quality. As an illustration, ImageCLEF 2018 working notes (task overviews and participant working notes) can be found within CLEF 2019 CEUR-WS proceedings.


Participants of this challenge will automatically be registered at CLEF 2019. In order to be compliant with the CLEF registration requirements, please edit your profile by providing the following additional information:

  • First name

  • Last name

  • Affiliation

  • Address

  • City

  • Country

  • Regarding the username, please choose a name that represents your team.

This information will not be publicly visible and will be exclusively used to contact you and to send the registration data to CLEF, which is the main organizer of all CLEF labs

Participating as an individual (non affiliated) researcher

We welcome individual researchers, i.e. not affiliated to any institution, to participate. We kindly ask you to provide us with a motivation letter containing the following information:

  • the presentation of your most relevant research activities related to the task/tasks

  • your motivation for participating in the task/tasks and how you want to exploit the results

  • a list of the most relevant 5 publications (if applicable)

  • the link to your personal webpage

The motivation letter should be directly concatenated to the End User Agreement document or sent as a PDF file to bionescu at imag dot pub dot ro. The request will be analyzed by the ImageCLEF organizing committee. We reserve the right to refuse any applicants whose experience in the field is too narrow, and would therefore most likely prevent them from being able to finish the task/tasks.


ImageCLEF 2019 is an evaluation campaign that is being organized as part of the CLEF initiative labs. The campaign offers several research tasks that welcome participation from teams around the world. The results of the campaign appear in the working notes proceedings, published by CEUR Workshop Proceedings (CEUR-WS.org). Selected contributions among the participants, will be invited for publication in the following year in the Springer Lecture Notes in Computer Science (LNCS) together with the annual lab overviews.


Contact us

We strongly encourage you to use the public channels mentioned above for communications between the participants and the organizers. In extreme cases, if there are any queries or comments that you would like to make using a private communication channel, then you can send us an email at :

  • Narciso Garcia, Professor, Dr., Grupo de Tratamiento de Imágenes, Dpto. Señales, Sistemas y Radiocomunicaciones, E.T.S. Ingenieros Telecomunicación, Spain, narciso@gti.ssr.upm.es

  • Ergina Kavallieratou, Associate Professor, Dr, AIlab, Department of Information & Communication Systems Engineering, University of the Aegean, Greece, kavallieratou@aegean.gr

  • Carlos Roberto del Blanco, Assistant Professor, Dr., Grupo de Tratamiento de Imágenes, Dpto. Señales, Sistemas y Radiocomunicaciones, E.T.S. Ingenieros de Telecomunicación, cda@gti.ssr.upm.es

  • Carlos Cuevas Rodríguez, Assistant Professor, Dr., Grupo de Tratamiento de Imágenes, Dpto. Señales, Sistemas y Radiocomunicaciones, E.T.S. Ingenieros de Telecomunicación, Spain, ccr@gti.ssr.upm.es

  • Nikos Vasillopoulos, Phd, Postdoc, AIlab, Department of Information & Communication Systems Engineering, University of the Aegean, Greece, nvasilopoulos@aegean.gr

  • Konstantinos Karampidis, Msc, Phd student, University of the Aegean, Greece, karampidis@aegean.gr

For questions over the Security task e-mail: Imageclefsecurity@aegean.gr

More information

You can find additional information on the challenge here: https://www.imageclef.org/2019/security