IMAGE-BASED CAPTCHA GENERATION SYSTEM

• US 20070201745A1
• Filed: 01/30/2007
• Published: 08/30/2007
• Est. Priority Date: 01/31/2006
• Status: Active Grant

• Current Assignee: Penn State Research Foundation
• Original Assignee: Penn State Research Foundation
• Inventors: Wang, James, Li, Jia, Datta, Ritendra
• Granted Patent: US 7,929,805 B2
• Time in Patent Office: Days
• US Class Current: 382/181
• CPC Class Codes: G06F 18/00 Pattern recognition

Abstract

In a system and method for the generation of attack-resistant, user-friendly, image-based CAPTCHAs (Completely Automated Public test to Tell Computers and Humans Apart), controlled distortions are applied to randomly chosen images and presented to a user for annotation from a given list of words. An image is presented that contains multiple connected but independent images with the borders between them distorted or otherwise visually obfuscated in a way that a computer cannot distinguish the borders and a user selects near the center of one of the images The distortions are performed in a way that satisfies the incongruous requirements of low perceptual degradation and high resistance to attack by content-based image retrieval systems. Word choices are carefully generated to avoid ambiguity as well as to avoid attacks based on the choices themselves.

Claims

1. A method of generating a Completely Automated Public test to Tell Computers and Humans Apart (CAPTCHA), comprising the steps of:

presenting at least one distorted photographic or graphical image along with a list of words, one of which best corresponds to the image; and

assuming that the recipient of the image is a human as opposed to a machine if the correct word is selected.

2. The method of claim 1, wherein the image is distorted using one or more of the following:

dithering, partitioning, quantization, noise addition, color re-mapping, and selective cut-and-resize.

3. The method of claim 1, further including the step of:

presenting a plurality of different images to a recipient to select a single one thereof.

4. The method of claim 1, further including the step of:

presenting a plurality of different images to choose from, the images being separated by borders which are distorted or otherwise visually obfuscated.

5. The method of claim 1, wherein the words are generated to avoid ambiguity with respect to the selected image.

12. The method of claim 5, wherein the process is repeated.

6. A method of generating a Completely Automated Public test to Tell Computers and Humans Apart (CAPTCHA), comprising the steps of:

presenting a plurality of different images to a recipient to select a single one thereof;

distorting the image selected, and presenting the distorted image along with a list of words, one of which best corresponds to the image; and

assuming that the recipient of the image is a human as opposed to a machine if the correct word is selected.

7. The method of claim 6, wherein the image is distorted using one or more of the following:

dithering, partitioning, quantization, noise addition, color re-mapping, and selective cut-and-resize.

8. The method of claim 6, further including the step of:

presenting a plurality of different images to a recipient to select a single one thereof.

9. The method of claim 6, further including the step of:

presenting a plurality of different images to choose from, the images being separated by borders which are distorted or otherwise visually obfuscated.

10. The method of claim 6, wherein the words are generated to avoid ambiguity.

11. The method of claim 6, wherein the image is distorted using content-based image retrieval and annotation.

13. A Completely Automated Public test to Tell Computers and Humans Apart (CAPTCHA) system, comprising:

a database for storing annotated images;

a processor for distorting one or more of the images;

a display for presenting one or more of the distorted images to a user along with a plurality of annotations to choose from; and

an input allowing a user to select the annotation that best corresponds to the image.

14. The CAPTCHA system of claim 13, wherein the processor is operative to:

display a composite containing a plurality of images.

15. The CAPTCHA system of claim 13, wherein the input allows a user to select one or more of the images from the composite prior to annotation.

16. The CAPTCHA system of claim 13, wherein the processor is operative to:

present a plurality of different images to choose from, the images being separated by borders which are distorted or otherwise visually obfuscated.