Freenet A Distributed Anonymous Information Storage and Retrieval

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Freenet: A Distributed Anonymous Information Storage and Retrieval System Ian Clarke, Oskar Sandberg, Brandon

Freenet: A Distributed Anonymous Information Storage and Retrieval System Ian Clarke, Oskar Sandberg, Brandon Wiley, Theodore W. Hong Presented by Zhengxiang Pan Jan. 30

Design Goals Anonymity for both producers and consumers of information n Deniability for storers

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

Architecture -overview A cooperative distributed file system n Location independence n Transparent lazy replication

Architecture -overview A cooperative distributed file system n Location independence n Transparent lazy replication n Local datastore & dynamic routing table n No privilege n No hierarchy n No central point n

Architecture –Keys and Searching n KSK: keyword-signed key Easy to remember n Problematic flat

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

Architecture –Retrieving data

Architecture –Retrieving data

Architecture –Storing data Calculate file key n Send insert message like request n If

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

Architecture –others n Managing data LRU: Least Recently Used Cache n Routing table entries:

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

Protocol details Flexible in transport mechanism n Node address e. g. tcp/192. 168. 1.

Protocol details Flexible in transport mechanism n Node address e. g. tcp/192. 168. 1. 1: 19114 n 64 -bit transaction ID n Hops-to-live & depth n

Performance analysis -convergence Time evolution of the request pathlength

Performance analysis -convergence Time evolution of the request pathlength

Performance analysis -scalability Request pathlength VS network size

Performance analysis -scalability Request pathlength VS network size

Performance analysis –fault tolerance Change in request pathlength under network failure

Performance analysis –fault tolerance Change in request pathlength under network failure

Performance analysis –small world model Distribution of link number among Freenet nodes

Performance analysis –small world model Distribution of link number among Freenet nodes

Security n Anonymity of requestors and inserters Key anonymity: vulnerable to dictionary attack n

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

More ? n http: //www. freenetproject. org/ n

More ? n http: //www. freenetproject. org/ n