Freenet File sharing for a political world

Freenet: A Distributed Anonymous Information Storage and Retrieval System I. Clarke, O. Sandberg, B. Wiley, and T. W. Hong

Reasons for development “The importance of the Free flow of information” Censorship by governments Restrictions due to copyright enforcement Napster lawsuits

Freenet Philosophy Communication is what makes us human Knowledge is good Democracy assumes a well informed population Censorship and freedom cannot coexist Anonymity is necessary to defeat censorship

Design Goals Anonymity for both producers and consumers of information Deniability for storers of information Resistance to attempts by 3 rd parties to deny particular information Efficient dynamic storage and routing Decentralization of all network features

Freenet as a layer 3/4 system Freenet is a network layer system that sits on top of TCP It does not provide any applications File-sharing, chatting, ing, and web- browsing have been built on top Routing similar to IP using RIP Unlike IP, all data sent must be stored on Freenet: no non-persistent transfers

The key idea Freenet files are stored and located by keys The keys are usually hashes of the files they represent (160-bit SHA1) called CHK Keys can be KSK which are stored and retrieved based on a text string Third type of key SSK, similar to a website. Key that is generated from combining a subspace hash with a text description.

Examples of three type of keys /TFE//thelist.html I,OejC1NKzRVt1GkRpcW0f4Q (06 Amerika - America.mp3) of-war

How a file is retrieved Obtain or calculate the binary key Check local datastore for key Send data-request to neighboring nodes Receive either data-reply or request-failed messages Message propagates as long as hops-to-live is positive

Middle nodes for a transfer Nodes not originally requesting or replying for a data transfer are middles nodes Middle nodes have routing tables that know where a specific hash-prefix might be found If the table entry returns not found, then try other connected nodes Similar to DNS recursive method, but willing to try other possibilities as well

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Failed file transfer Time to report this error message: ~ 5 minutes

Successful file transfer Time to report this page: ~ 2 minutes

Storing data The first step is to attempt the retrieval of the key to be stored When the retrieve fails (it should), the data is sent along the retrieval path up to a certain HTL and inserted into every node’s datastore Nodes along this path can decide randomly to claim ownership of the new data to maintain anonymity

Adding a new node A node must have the address of one other node to join Then generates a random seed for itself Contacts neighbor and announces itself Neighbor contacts all neighbors with the announcement, etc. Some form of cryptography verifies that nodes do not modify announcement

Managing data Clearly a node’s data store is finite Uses LRU cache policy to decide when to delete keys Keys never requested eventually disappear from Freenet entirely Keys frequently requested are stored in many nodes to provide redundancy

Performance Freenet is not designed to be efficient The number of hops to frequent data is designed to decrease over time Designed to scale to millions of nodes Large amount of interconnectivity allows failure of many nodes Possible denial of service attacks

Current Implementation Freenet engine and web-proxy are written in java and bundled for Windows and UNIX Large CPU usage, engine needs almost 100 threads, 50+ TCP connections to work well Applications add significant CPU and threads These restrictions cause most Freenet users to not be online very often

What is available on Freenet? Copyrighted music, movies, software Underage pornography Plans for and accounts of federal crimes Anti-government writings Anything else that is illegal in any country A few mirrors of legal data

Conclusion Freenet is an excellent way to store data while remaining anonymous Significant work has been done to have fault- tolerance, intelligent routing Efficiency is not a top priority The system could be usable today, yet too many transient nodes