Friend-to-friend

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A friend-to-friend (or F2F) computer network is a particular type of anonymous P2P in which people use direct connexions with their "friends". F2F softwares only allow people you trust (using IP addresses or digital signatures you trust) to exchange files directly with your computer. Then your friends'own friends (and so on) can indirectly exchange files with your computer, never using your IP address.

Dan Bricklin introduced the term F2F in August 11, 2000 bricklin.com

MUTE, ANts P2P, Metanet, and WASTE are examples of F2F networks.

Uses of F2F

• F2F prevents random people from proving that your IP address can effectively be used to get some controversial files (and as soon as you know all the IP addresses of your friends, you can even use a firewall to block all the other addresses from accessing your F2F port)

• F2F that use link encryption but no end-to-end encryption (Metanet,Mute and Waste) allow you to control (using your favorite sniffer) what kind of files your friends exchange with your node, in order to stop them from exchanging files that you disapprove of. Stop them by removing their public keys or by using a firewall to slow or stop their connexion with your node. You can even give their IP to the police, but since they are your friends you should kindly warn them first. Maybe one of their own friends made them do that. Now they can warn this friend in turn. And so on.

• Far less security problems: since only your friends can connect to your node, no random cracker can try to break into your computer by connecting with your P2P node and then using a bug in the communication part of the software. Dangerous documents (i.e. with viruses, buffer overflow attacks...) could even be avoided using strong reputation based networks (see "Future uses" below)

• Third party storage (e.g. FTP, Web, email servers) can be used to get faster downloads and to prevent your ISP from logging your friends'IP addresses (using encryption with the third party)

Future uses of F2F

• Strong encrypted F2F networks will mainly use strong symmetric encryption (in particular, the provably secure one time pad) for every link. This can only be achieved in real F2F networks since when you communicate with someone you never met in person, you have to use asymmetric encryption (along with some serious man in the middle problems).

• A very strong digital reputation based network could be built using a strong encrypted F2F network: each document on this network would be automatically given a new "trust percentage" by each node that forwards it ( new_trust% = old_trust% * local_reputation%_of_the_provider). If a document appears to be incorrect then you can manually decrease the local reputation% of the friend that sent it to you (the provider) and decrease the trust% of this document. You can even block this document from being exchanged again through your node.

• Such a strong reputation network could be safely used to exchange electronic money with fewer greed and corruption: altruists.org

What F2F is not

• a F2F is more powerful than an encrypted private FTP server. Your F2F node can forward a file (or a request for a file) anonymously between two of your friends (when forwarding a file or a request between them, your node doesn't tell any of them who is the other and what is the other address). Then these friends'nodes can in turn forward anonymously this same file (or request) to several of their own friends. And so on.

• a F2F is different from a private DirectConnect hub, since inside a DC hub everyone can know and use all the IP addresses of all the users (even when the address is from a friend from a friend from a friend..., someone you may never know)

• GNUnet and Freenet are not F2F because for efficiency reasons (path shortening) they allow some random nodes to connect directly to your node, thus knowing your IP and which files you can provide.

Some security breaches in current networks and their solutions

Besides the fact that current networks don't use provably secure crypto (see "Future uses" above), here are some other breaches:

• In countries where anonymous P2P is forbidden, your ISP can suspect that you use F2F since the networks don't use the default standard ports of popular encrypted programs like webphones or webcams (this solution, along with using a layer of the same encryption as webphones, would be a very simple form of steganography). Using a third party storage (F3F) is a similar solution with more advantages. Networks that use generic VPN software as Metanet does, are less vulnerable to this issue.
• Traffic analysis of all your links by your ISP could easily show that you automatically forward some documents. Solution: add padding bytes to files, and even when you get no more request from a friend, send him some files similar to the ones he usually asks for (this solution is not far from how Konspire2b already works now)
• In countries where strong crypto is forbidden (or where you can be forced to give your keys), serious steganography should be used (even for storing files in your hard disk, since it could be seized)

These breaches are not F2F specific: they are shared with most of the current P2P networks.