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Access Control to BitTorrent Swarms using Closed Swarms
Dr. Njål BorchNorthern research institute,
Tromsø, Norway
Why access control?
• No access control– Limited commercial possibilities
• DRM– Control content, not distribution– Limits usability from end user perspective
• Closed swarms– Distributed access control mechanism– Differentiated services– Control network resources
DRM
• Manage restrictions on content• Favoured by Broadcast TV
– Non-authorized users costs zero– Loss of profit if people break it
• But online (unicast)?– Non-authorized user costs money– Accumulates high bandwidth cost if broken or circumvented
Control access to resources
• Central system– Authentication service– Username/password– Fairly simple solution– Accumulates bandwidth costs
• P2P system– Cost saving– Appealing scalability properties– Centralized access control on central bits– Leaking nodes
• But: Both (all really) systems can experience leaking content
Closed Swarms – the Idea
Create a flexible authentication mechanism for P2P which is both scalable and allows for experimental and innovative business models.
The nodes
AN L
The Math
The Math
The Math
So basically...
• Non-authorized nodes can be of use– They can even be explicitly allowed
• Can subsidize bandwidth to selected nodes
The basics
Proof of
AccessNode Key
Swarm
Swarm Key
Node
The Protocol
Node A- Generate and send Nonce
- Send signed PoA
- Verify PoA, allow upload
Node B
- Generate and send Nonce
- Verify PoA, allow upload- Send signed PoA
Points
• Seeds do not need to sign and send PoAs• No central access required to validate PoAs• No need to know a node's keys in advance• Only performed on connect (handshake)• BitTorrent implementation backwards compatible
– But non-CS clients are non-authorized
• Allows easy addition of seeds– Provide data or a PoA for the seedbox
Possible applications
• Sell guarantees– Free user gets community service. Might VoD, might not.– Paying customer is guaranteed high speed seeds, will VoD.
• Sell guarantees 2– Home user can watch a live event, if there is capacity– A venue can buy access to an event, and is guaranteed seeds.
• Closed group sharing– Only authorized nodes are allowed access
• Combine with Scalable video coding (SVC)– SD for free users, pay for HD