NOTICE (10/22/00):

• SARI is now version 1.1 !!! Please update to this new version.
• A benchmark of SARI 1.1 is available at http://www.ctr.columbia.edu/sari/benchsari.

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 cut tail, a watermarked SARI image can detect malicious crop-and-replacement manipulations and recover an approximated original image on the altered area. Another important feature of SARI is its thorough compatibility to JPEG lossy compression. SARI authenticator can sensitively detect malicious changes while accepting alteration introduced by JPEG lossy compression. The lowest acceptable JPEG quality factor depends in a adjustable watermarking strength controlled 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.

==> Click here to see a benchmark of SARI 1.1.

You are invited to test this SARI system. Now, you can download the SARI embedder to your machine, embed watermark to your image, manipulate it, and then use our on-line authenticatior. Your feedback on the system performance, bugs, potential applications, etc , will be very appreciated.

Installation and Execution:

Step 1: Download SARI 1.1 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 1.1 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 open the MS-DOS prompt and change directory to the SARI directory. Type "sariwater" to launch watermark embedder.

Step 4: Using SARI 1.1 Embedder, you can load your local image, choose the type of watermarks for embedding, and then click "watermark it." SARI 1.1 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 and possible lossy compression. (from BMP to JPG)

(2) Crop-and-replacement and then format transformation plus possible lossy compression.

Use Photoshop to Crop & Replace Part of Image Content

After manipulation, images can be saved as BMP or JPEG. (The lowest JPEG compression quality that a SARI image can survive can be a robustness parameter set in the embedder.)

Manipulated and JPEG-Compressed Image

Authentication:

Launch SARI 1.1 On-line Authenticator -- It can authenticate your image on-line. This on-line version only accepts 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.
• 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 Resource Page -- including links to an introduction of multimedia authentication and a bibliography of multimedia authentication research papers.

Contact Us:

• SARI includes technologies with patent applications pending.
  
• For technical questions, please contact Ching-Yung Lin or Shih-Fu Chang.
  
• For licensing questions, please contact Robert Schleelein of Columbia Innovation Enterprise (CIE), Ching-Yung Lin or Shih-Fu Chang
  

Webpage Copyright 2000-2001 by Ching- Yung Lin, ADVENT Lab, Columbia Univeristy Last updated : Oct 22, 2000 If you are interested in the multimedia authentication topics, please contact me or sign my guestbook !!