Moderation and rich metadata

Currently every peer can publish .torrent files using BuddyCast. No moderation mechanism exists yet.

Research problem: the metadata infrastructure for Video on Demand

Research question : Design, implementation, and evaluation of an efficient epidemic protocol for distribution of rich-metadata with pollution prevention measures

Operational Python code

Performance analysis results

• Propagation speed of moderation
• Moderation participation (<0.1%, 1%, 2%)
• Malicious peer levels (<0.1%, 1%, 2%)

Related Gossip work

Update on progress

We have chosen to design and implement the simple moderation protocol using gossiping (based on BuddyCast). Peers can create and receive moderations, which contain extra data for a given torrent:

• spoken language
• subtitles
• description
• thumbnail
• tags

We have chosen not to enable peers to change the title of a torrent. This would make finding a torrent with a badly moderated title very difficult. Furthermore we have decided not to include majority voting as a tie-breaker between moderations, but to use the last moderation. This is far more scalable when there is no trust mechanism. (Determining the majority in a non-secure environment requires either trust or every peer gathering all the moderations itself.)

As a pollution prevention measure we use blacklisting. Users can block moderators that send bad moderations. This is done for the PermID and also for the IP-address of the peer. To further prevent the propagation of bad moderations we do not automatically forward moderations. Peers have to indicate that they are willing to forward moderations for certain moderators.

Moderations are signed using the Elliptic Curve Digital Signature Algorithm which is also used to verify the PermIDs. This enables the peers to verify the authenticity of the message even if it is forwarded by a third party.

The protocol allows for rate-control to minimize bandwidth consumption.

For a more detailed explenation of the protocol, we refer the reader to the ModerationCAST design document

Thesis outline

• Introduction
• Problem Description section
  Rich meta-data with pollution prevention
• Design of ModerationCast?
  A complete solution is too hard, we take the first step
  Smaller focus: How to efficiently distribute user-generated annotations?
  Incremental improvement of deployed system.
  Algorithms: (Discuss alternatives, pick a winner)
  • Priorities of information (newest first, random old stuff)
  • Rate control (sliding window, forwarders principle+voting)
  • Security framework (signature implementation+voting)
• Experiments and evaluation
  Trace-based simulations
  Spreading speed(torrent/moderation),

Introduction of Video on Demand in P2P by Vincent