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Towards Digital Rights Protection in BitTorrent-like P2P Systems Xinwen Zhang Samsung Information Systems America Dongyu Liu and Songqing Chen George Mason.

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Presentation on theme: "Towards Digital Rights Protection in BitTorrent-like P2P Systems Xinwen Zhang Samsung Information Systems America Dongyu Liu and Songqing Chen George Mason."— Presentation transcript:

1 Towards Digital Rights Protection in BitTorrent-like P2P Systems Xinwen Zhang Samsung Information Systems America Dongyu Liu and Songqing Chen George Mason University Zhao Zhang Iowa State University Ravi Sandhu University of Texas at San Antonio, MMCN 2008

2 BitTorrent P2P By the end of 2004, BitTorrent (BT) was accounting for as much as 30% of all Internet traffic. –P2P traffic is 60% of all Internet traffic –Data from CacheLogic compared to , FTP and the Web in general.

3 Trends BT Keeps Growing –In May 2006, the average torrent had 817,588 people participating. 12 months later, that figure had jumped to 1,357,318 seeders and leechers: a 66 percent year- over-year growth rate. –P2P applications account from anywhere between 50 percent and 90 percent of all Internet traffic BitTorrent accounted for between 50 percent to 75 percent in 2006 –http://arstechnica.com/news.ars/post/ p2p-responsible-for-as-much-as-90-percent-of- all-net-traffic.html P2P file sharing Traffic shifts from small file-sizes to huge file-sizes –From music to movies, TV shows, and full albums

4 Current Status There are some legal content sharing –Open source software distributions However, most content shared with BT are not copyright-protected. No practical DRM mechanism built for BT –Due to its highly distributed environment and uncontrolled peer activities

5 Motivation & Challenges Enable DRM in BT-like P2P system –Leverage efficiency of BT for legal content distributions –Enable new business model with P2P Challenges: –Existing DRM schemes are client-server model –Open platforms of peers – –Should be no demanding infrastructure changes P2P users are loath to change.

6 Approach & Features Approach: –An re-encryption crypto scheme based on –An re-encryption crypto scheme based on asymmetric encryption algorithm – –Each piece is re-encrypted at runtime before a peer uploads it to any other peer so that the decryption keys are unique for both different peers and difference pieces. Features: –Leverage the lightly-centralized tracker site to store and distribute re-encryption keys Typically is trusted by content provider or owner – –Any user can take part in the content distribution while only legitimate users can access the plaintext

7 BitTorrent s Basic Idea To best utilize parallel downloading, file is treated as many pieces: –Using SHA-1 to ensure every piece s data integrity –Using rarest first strategy for piece selection to speed up distribution Using a tit-for-tat algorithm (choking for the lowest speed uploader) to encourage uploading Typically there re Web servers to serve.torrent metainfo file Tracker: maintain all peers IP/port information, so each peer can find others Downloaders (leecher/seed) as peers connected to each other

8 Content Distribution

9 Overall Architecture Web page with link to.torrent A B C Peer [Leech] Downloader US Peer [Seed] Peer [Leech] Tracker Web Server.torrent

10 Overall Architecture Web page with link to.torrent A B C Peer [Leech] Downloader US Peer [Seed] Peer [Leech] Tracker Get-announce Web Server

11 Overall Architecture Web page with link to.torrent A B C Peer [Leech] Downloader US Peer [Seed] Peer [Leech] Tracker Response-peer list Web Server

12 Overall Architecture Web page with link to.torrent A B C Peer [Leech] Downloader US Peer [Seed] Peer [Leech] Tracker Shake-hand Web Server Shake-hand

13 Overall Architecture Web page with link to.torrent A B C Peer [Leech] Downloader US Peer [Seed] Peer [Leech] Tracker pieces Web Server

14 Overall Architecture Web page with link to.torrent A B C Peer [Leech] Downloader US Peer [Seed] Peer [Leech] Tracker pieces Web Server

15 Overall Architecture Web page with link to.torrent A B C Peer [Leech] Downloader US Peer [Seed] Peer [Leech] Tracker Get-announce Response-peer list pieces Web Server

16 Enable DRM for BT Overall DRM requirements: –Encrypted content –Flexible policy management (e.g., through license file) –Usage tracking Three different DRM models – –Model 1: encode policy in object Static policy, no update, no tracking – –Model 2: separated policy file with object Same object copy for all users (same encryption key) Break-once-run-everywhere – –Model 3: separate policy from object, and each user obtains a different copy of the object each object is encrypted with a different key Or each encrypted object has a unique ID Strong tracking Strongest DRM scheme

17 Case Study: Windows Media Digital Rights Management

18 Enable Strong DRM in BT Overall requirements: –Confidentiality of data transition between any two peers –no-linkable content secrecy –Immune to passive attacks with intercepted messages. –Immune to compromised peers. –Immune to collusion between any number of peers.

19 Some Naive Solutions Symmetric key algorithm – –Each pair of peers shares a symmetric key – –Key management is an issue – –a peer can share a file piece only after decryption, which makes the system vulnerable to the attack that a malicious peer could upload/distribute plain file pieces to others Traditional public-key algorithm – –Each peer has a public/private key pair. – –Same problems

20 Secure BT scheme for Strong DRM

21 Secure BT Scheme

22 Security of the Scheme

23 Performance Cryptography performance –PEnc is only performed by the initial seed. –PDec is only performed when playing –Selective encryption and pre-processing can increase the speed.

24 Performance Communication overhead measurenent in PlanetLab: – –4 dedicated seeds are set up with an uploading speed of 200 KB/s. – –Randomly selected 120 PlanetLab nodes are used as downloaders, from Asia, Europe, and United States. – –The object is a 640-MB file. Both the seeds and the tracker are running Celeron CPU 2.4 GHz with 1 GB memory, and Linux Fedora and Python – –Change piece size to simulate different download traffic from seeds. 512KB vs. 120 nodes 256KB vs. 240 nodes 128KB vs. 480 nodes 64KB vs. 960 nodes 32KB vs nodes

25 Performance Slightly increase on tracker response time for single download request Less than 10% system throughput decrease

26 Conclusions BT high efficiency has not been leveraged to distribute the majority of copyrighted digital content over the Internet. We propose a security mechanism based on the existing BT infrastructure to enable copyright protection. We have implemented a prototype system and conducted real experiments in PlanetLab. The evaluation results show that our scheme can still achieve comparable content distribution efficiency to the original BT system. – –That is, to enable DRM, our proposed scheme causes less than 10% degradation of the system throughput. We are further optimizing the system performance We are exploring DRM mechanism on tracker-less BT systems

27 Thank you ! Q & A


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