1. Safeguarding and Charging for Information on the Internet Hector Garcia-Molina, Steven P. Ketchpel, Narayanan Shivakumar Stanford University Presented by: Min Ren

2. Outline Introduction E-Commerce Components Safeguarding Information Conclusion

3. Introduction With the rapid expansion of the Internet Population, publishers are tempted to publish on the Internet to cut down on printing and distribution costs. They need an e- commerce infrastructure! With the documents transmitted electronically, one concern is how to safeguard the information. This article addresses this problem by providing possible solutions.

4. E-Commerce Components Shopping Systems These mechanisms enable a customer to search for a product and select goods for purchase. Payment Systems These mechanisms enable a customer to make the payment. Delivery Systems These mechanisms deliver goods to customers. Special safeguards are required for e-contents.

5. Risks of e-content Delivery when the information is transmitted electronically, provider runs the risk of the content being copied and made available to everyone through the World Wide Web.

6. Possible Solutions Copy-protection strategies (prevention) 1. Physical isolation (e.g. on CD-ROMs accessible only through special-purpose systems) 2. Special-purpose hardware for authorization. 3. IBM’s Cryptolopes (content is encrypted; users are given a decryption key after their payment; users view the content through a “trusted viewer”).

7. Possible Solutions 1.Watermarks (detect additional information in distributed copies) 2. Copy Detection (detect exact copies by comparison to originals) Watermarks and Copy Detection (detection):

8. CDS (Copy Detection System) Registration Repository a database to keep registered documents, which are checked with the query documents to find possible copies. Crawler a mechanism to crawl through the WWW and present a stream of documents and images to the CDS. Similarity Matcher a mechanism to compare the query object to objects in the database, if they are match, the owner is notified.

9. SCAM SCAM (Stanford Copy Analysis Mechanism) This is a “proof-of-concept” CDS system implemented by Stanford for text documents. Example Given a document that may have a copy at one of several databases B1,….,Bi. How can we find this copy?

10. SCAM ― Registration  The publisher registers the document at the Registration Server.  “Chunking” is a method used to break documents into smaller primitives.  The document is chunked and the primitives are stored in the database. ― Crawling How to choose a Bi for finer testing? Firstly, to generate a detection query based on important words in the document, submit it to each database, choose the database with high number of documents; Secondly, generate an extraction query to extract the documents that may be copied.

11. Implementation of CDS ― Similarity Matching  Chunking  The query object is chunked and compared with the document registered in the database;  The same rules of chunking in registration step is applied here.  Filtering Expensive Tests  “ false negatives” (fail to detect documents that did overlap significantly).  “false positives” (indicate two documents overlap when they do not).  We can compose these tests to obtain better accuracy and performance.

12. Conclusion This paper addressed some problems in building a good commerce infrastructure. The measures of how to efficiently safeguard illegal copies are discussed.

13. Questions?? What is the relationship between watermarks and CDS?