Freenet: A Distributed Anonymous Information Storage and Retrieval System

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Freenet A Distributed Anonymous Information
Storage and Retrieval System

• Ian Clarke, Oskar Sandberg, Brandon
  Wiley,Theodore W. Hong
• Presented by Zhengxiang Pan
• Jan. 30

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Design Goals

• Anonymity for both producers and consumers of
  information
• Deniability for storers of information
• Resistance to attempts by third parties to deny
  access to information
• Efficient dynamic storage and routing of
  information
• Decentralization of all network functions

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Architecture -overview

• A cooperative distributed file system
• Location independence
• Transparent lazy replication
• Local datastore dynamic routing table
• No privilege
• No hierarchy
• No central point

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Architecture Keys and Searching

• KSK keyword-signed key
• Easy to remember
• Problematic flat global namespace
• SSK signed-subspace key
• Personal namespace
• Manage directory
• CHK content-hash key
• Pseudo-unique file key
• Useful for updating and splitting

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Architecture Retrieving data
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Architecture Storing data

• Calculate file key
• Send insert message like request
• If all clear send the data to insert
• Stored in each node alone the path
• Each node add entry to routing table associating
  the key and the data source (can be random
  decided)

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Architecture others

• Managing data
• LRU Least Recently Used Cache
• Routing table entries in same fashion but will
  be kept longer
• Encrypted contents
• Adding nodes
• Find existing nodes by out-of-band means
• New-node announcement
• Consistent random key for new node in routing
  table

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Protocol details

• Flexible in transport mechanism
• Node address e.g. tcp/192.168.1.119114
• 64-bit transaction ID
• Hops-to-live depth

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Performance analysis -convergence
Time evolution of the request pathlength
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Performance analysis -scalability
Request pathlength VS network size
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Performance analysis fault tolerance
Change in request pathlength under network failure
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Performance analysis small world model
Distribution of link number among Freenet nodes
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Security

• Anonymity of requestors and inserters
• Key anonymity vulnerable to dictionary attack
• Sender anonymity local eavesdrop
• Anonymity of storer encrypted contents
• Malicious modification keys
• Denial-of-service a large number of junk files

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• More ?
• http//www.freenetproject.org/