1 / 1

Protecting the Web with Transparent Proof-of-Work

Protecting the Web with Transparent Proof-of-Work. Web Server. URL w/ valid PoW. Content. Solution Scripts. Content. mod_kaPoW. Clients. URL w/ invalid PoW. Error Page. Error Page. Wu-chang Feng, Tom Shrimpton, Ed Kaiser (student) { wuchang,teshrim,edkaiser}@cs.pdx.edu.

asis
Download Presentation

Protecting the Web with Transparent Proof-of-Work

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Protecting the Web with Transparent Proof-of-Work Web Server URL w/ valid PoW Content Solution Scripts Content mod_kaPoW Clients URL w/ invalid PoW Error Page Error Page Wu-chang Feng, Tom Shrimpton, Ed Kaiser (student){wuchang,teshrim,edkaiser}@cs.pdx.edu • 1. Problem: Attacks on the Web • 2. CAPTCHA to the rescue? • Problem #1: Inaccessible • Problem #2: Economics broken • Fixed human workload • Outsourced for under $0.01 per CAPTCHA • Mechanical Turk, getafreelancer.com • Problem #3: Hackers are solving the hard AI problem • Yahoo! CAPTCHA broken 1/16/2008 • http://network-security-research.blogspot.com/ • Windows Live and Google CAPTCHAs broken 2/6/2008 , 2/22/2008 • http://www.websense.com/securitylabs/blog/ • Many others Click fraud Distributed Denial-of-Service Comment spam Ticket purchasing robots • 3. What about Proof-of-Work (PoW)? • Addresses Problem #1: No user-interface issues • Addresses Problem #2: Variable workload • Addresses Problem #3: Hard cryptographic problem • Q: Why is the landscape littered with unused PoW protocols? • Hashcash, TLS puzzles, TCP puzzles, IP puzzles, Public work • A: PoW requires protocol changes and universal deployment • CAPTCHAs do not! • 4. mod_kaPoW • Apache module for embedding PoW challenges into URLs • Leverage ubiquitous JavaScript support to deploy PoW • Server dynamically embeds PoWs in embedded URLs • Client-side JavaScript solver must calculate answers for access • No network protocol changes • No web browser changes • No web server content changes 5. Example New approach • Proof-of-Work without protocol changes • Dynamic embedding of PoW into URLs Research Impact • Deployable alternative to CAPTCHAs • New weapon against today’s web attacks • 6. Implementation • JavaScript solver (kaPoW.js) • “onLoad” event handler to solve PoW challenges for embedded images • “onClick” event handler to solve challenges for embedded links • Solve routine finds a value A, such that • SHA1(NC || URL || A)  0 mod DC • DC client-specific server-assigned difficulty • NC client-specific server-generated nonce • mod_kaPoW Apache module • 8. Future work • Policy module for setting per-client Dc • Client history • Client reputation • Client location • Request type • Resource requested • Adding to applications • Forums (phpBB) • Wikis (MediaWiki) • Blogs (WordPress, Slashcode) • Web 2.0 / AJAX • Economic analysis • What is the cost of idle CPU cycles? • Markets based on CPU cycles 7. Thwarting DoS • 10. Publications • E. Andreeva, G. Neven, B. Preneel T. Shrimpton, “Seven-Property Preserving Iterated Hashing: ROX”, ASIACRYPT 2007. • T. Ristenpart, T. Shrimpton, “How to Build a Hash Function From Any Collision-Resistant Function”, ASIACRYPT 2007. • W. Feng, E. Kaiser, “The Case for Public Work”, Global Internet 2007. • E. Kaiser, W. Feng, “mod_kaPoW: Protecting the Web with Transparent Proof-of-Work”, in submission. • 9. Availability • Demo site • http://kapow.cs.pdx.edu • Non-commercial source release • In progress

More Related