Telecommunications Lab
(Lehrstuhl für Nachrichtentechnik)
Saarland University, NTF I - 6.2 Computer Science
Campus C6 3, Floor 10
P.O. Box 151150
66041 Saarbrücken

WS 2006/07

Main Seminar "Attacking a Visual CAPTCHA"

Supervisor: Dr. Igor Fischer

Overall organization

The seminar will be executed during the semester, with meetings approximately every two weeks. Extensive homework is expected between the meetings. The final meeting is a longer block where the students present their work. The seminar is divided into following topics:

Nr.   Topic   Student  
1.   Generalized shape context    
2.   Fast pruning and pruning with bigrams    
3.   Detailed matching (bipartite graph matching)    
4.   Finding letter hypotheses    
5.   Extracting candidate words    
6.   Scoring the candidates and choosing the best    
7.   Layers of words    
8.   Scoring the candidates and choosing the three best    
9.   Interpolating the background    

For each topic one student:
  • implements and tests a block in the CAPTCHA-breaking pipeline (during the semester)
  • writes a report on the purpose and capabilities of his module
  • reports this orally (block seminar at the end of semester)


The organizational flow of the seminar is the following:

Date   Time   Place   What
until 24.10.       www   On-line registration
24.10.   16:00   C6 2 U.26   Kick-Off meeting: Introduction.
24.10. - 14.11.           Reading and understanding the background literature. Writing a short informal summary of the functionality and interfaces of one's part.
14.11.   14:00   C6 2 U.26   Briefly and informally report about one's part and its interfaces. Get a short introduction to Matlab and Subversion. Establish interfaces and naming conventions.
14.11. - 28.11.           Program the interfaces (at least!) in Matlab. Document them and check them into Subversion repository.
28.11.   16:00   C6 2 U.26   Testing the interfaces, discussing problems.
28.11. - 12.12.           Writing one's block and testing it on suitable data. Extensively document the Matlab code (comments!). Checking the code into the repository. Writing an extended description of its function, challenges encountered, properties...
12.12.   16:00   C6 2 U.26   Seminar meeting: Testing the whole pipeline.
12.12. - 09.01.           Debugging the code, making sure everything works perfectly. Checking the code into the repository. Writing the seminar paper and the presentation.
23.01.   16:00   C6 2 U.26   Final build and testing.
23.01. - 30.01.           Finalizing the seminar paper and the presentation.
30.01.   07:00   e-mail   Submitting the paper and the presentation.
06.02. - 07.02.   16:00   C6 2 U.26   Seminar presentation.