Description:

SARI (Self-Authentication-and-Recovery Images) is a semi-fragile watermarking technique that gives "life" to digital images. Like a gecko can recover its cutted tail, a watermarked SARI image can detect malicious crop-and-replacement manipulations and recover an approximated original image on the altered area. Another important characteristic of SARI is its thorough compatibility to JPEG lossy compression. SARI authenticator can sensitively detect malicious changes while accepting alteration introduced by JPEG compression. The lowest acceptable JPEG quality factor depends on a adjustable watermarking strength in the embedder. SARI images are secure because the embedded watermarks are dependent on their own content (and on their owner).

==> Click here to see a brief technical description.

You are welcomed to test this SARI system. Now, you can download the SARI embedder to your machine, embed watermark to your image, manipulate it, and then authenticate it on-line. Your feedback on its system performance, usefulness, bugs, promising application, your expectation, etc, will be very appreciated.

Installation and Execution:

Step 1: Download SARI Embedder -- PC Windows version

Step 1-1: SARI Embedder needs Java Virtual Machine. If you need it, click here to download Java 2 Runtime Environment..

Step 2: Use Winzip to unzip the SARI Embedder. Click Check-Out to generate a group named SARI. If CheckOut does not work, you can click EXTRACT to extract these files to a new directory.

Step 3: In the SARI Group, double-click "sariwater" to launch watermark embedder. (Use "sariwater-j2" if you use Java JDK 1.2.) If the Winzip doesn't generate a group, then please open the MS-DOS prompt and change directory to the SARI directory. Type "sariwater" to launch watermark embedder.

Step 4: Using SARI Embedder, you can load your local image, choose the type of watermarks for embedding, and then click watermark it. SARI Embedder accepts Black-and-White/ Indexed Color/ True Color Images of the following formats: BMP/ GIF/ JPG/ PPM/ PGM.
[ Click here --> Tips and Performance Charts for SARI Embedder ]

Step 5: Save the watermarked image as BMP format. This image will be able to authenticate and/or recovery itself from malicious manipulations. The watermarked image is referred as a SARI image.

Manipulation:

You can manipulate a SARI image using a general image editing/manipulation tool (e.g. Photoshop). SARI is designed especially for detecting the malicious crop-and-replacement manipulation.

You can try the following two kinds of test:

(1) Format transformation only. (from BMP to JPG)

(2) Crop-and-replacement and then do the format transformation.

After manipulation, images can be saved as BMP or JPEG. (The extent of surviving low quality JPEG compression depends on the robustness of embedded watermark.)

Authentication:

Launch Authenticator -- It can authenticate your image on-line. This on-line authenticator only accept BMP and JPEG formats.

Example: the authentication results of the above image

==> Click here to see the authentication result.

==> Click here to see the recovered image.

• This on-line shareware version of embedder and authenticator is for demonstration/evaluation only. The formal version includes key management functionalities that provide restricted access control to the embedding and authentication processes.
• If you find any problem while running these programs, please inform me. Your help will be very much appreciated.
• This system is partially described at Ching-Yung Lin and Shih-Fu Chang, "Semi-Fragile Watermarking for Authenticating JPEG Visual Content," SPIE Security and Watermarking of Multimedia Contents II, EI '00, San Jose, CA, Jan. 2000. [download]
• Multimedia Authentication Main Page -- including links to an introduction of multimedia authentication and a bibliography of multimedia authentication research papers.

Copyright 2000-2005 by Ching- Yung Lin, ADVENT Lab, Columbia Univeristy Last updated : Aug 10, 2000 If you are interested in the multimedia authentication topics, please contact me or sign my guestbook !!