Note: This page is not up-to-date. See the roadmap for current plans.
Below is a more detailed (yet still incomplete) discussion of the major areas of future development on the core I2P network, spanning the plausibly planned releases. This does not include stego transports, porting to wireless devices, or tools to secure the local machine, nor does it include client applications that will be essential in I2P's success. There are probably other things that will come up, especially as I2P gets more peer review, but these are the main 'big things'. See also the roadmap. Want to help? Get involved!
NetworkDB and profile tuning and ejection policy for large nets
Within the current network database and profile management implementation, we have taken the liberty of some practical shortcuts. For instance, we don't have the code to drop peer references from the K-buckets, as we don't have enough peers to even plausibly fill any of them, so instead, we just keep the peers in whatever bucket is appropriate. Another example deals with the peer profiles - the memory required to maintain each peer's profile is small enough that we can keep thousands of full blown profiles in memory without problems. While we have the capacity to use trimmed down profiles (which we can maintain 100s of thousands in memory), we don't have any code to deal with moving a profile from a "minimal profile" to a "full profile", a "full profile" to a "minimal profile", or to simply eject a profile altogether. It just wouldn't be practical to write that code yet, since we aren't going to need it for a while.
That said, as the network grows we are going to want to keep these considerations in mind. We will have some work to do, but we can put it off for later.
Security / anonymity
Full blown n-hop restricted routes with optional trusted links
The restricted route functionality described before was simply a functional issue - how to let peers who would not otherwise be able to communicate do so. However, the concept of allowing restricted routes includes additional capabilities. For instance, if a router absolutely cannot risk communicating directly with any untrusted peers, they can set up trusted links through those peers, using them to both send and receive all of its messages. Those hidden peers who want to be completely isolated would also refuse to connect to peers who attempt to get them to (as demonstrated by the garlic routing technique outlined before) - they can simply take the garlic clove that has a request for delivery to a particular peer and tunnel route that message out one of the hidden peer's trusted links with instructions to forward it as requested.
Hashcash for routerIdentity, destination, and tunnel request
Within the network, we will want some way to deter people from consuming too many resources or from creating so many peers to mount a Sybil attack. Traditional techniques such as having a peer see who is requesting a resource or running a peer aren't appropriate for use within I2P, as doing so would compromise the anonymity of the system. Instead, we want to make certain requests "expensive".
Hashcash is one technique that we can use to anonymously increase the "cost" of doing certain activities, such as creating a new router identity (done only once on installation), creating a new destination (done only once when creating a service), or requesting that a peer participate in a tunnel (done often, perhaps 2-300 times per hour). We don't know the "correct" cost of each type of certificate yet, but with some research and experimentation, we could set a base level that is sufficiently expensive while not an excessive burden for people with few resources.
There are a few other algorithms that we can explore for making those requests for resources "nonfree", and further research on that front is appropriate.
Advanced tunnel operation (batching/mixing/throttling/padding)
To powerful passive external observers as well as large colluding internal observers, standard tunnel routing is vulnerable to traffic analysis attacks - simply watching the size and frequency of messages being passed between routers. To defend against these, we will want to essentially turn some of the tunnels into its own mix cascade - delaying messages received at the gateway and passing them in batches, reordering them as necessary, and injecting dummy messages (indistinguishable from other "real" tunnel messages by peers in the path). There has been a significant amount of research on these algorithms that we can lean on prior to implementing the various tunnel mixing strategies.
In addition to the anonymity aspects of more varied tunnel operation, there is a functional dimension as well. Each peer only has a certain amount of data they can route for the network, and to keep any particular tunnel from consuming an unreasonable portion of that bandwidth, they will want to include some throttles on the tunnel. For instance, a tunnel may be configured to throttle itself after passing 600 messages (1 per second), 2.4MB (4KBps), or exceeding some moving average (8KBps for the last minute). Excess messages may be delayed or summarily dropped. With this sort of throttling, peers can provide ATM-like QoS support for their tunnels, refusing to agree to allocate more bandwidth than the peer has available.
In addition, we may want to implement code to dynamically reroute tunnels to avoid failed peers or to inject additional hops into the path. This can be done by garlic routing a message to any particular peer in a tunnel with instructions to redefine the next-hop in the tunnel.
Stop & go mix w/ garlics & tunnels
Beyond the per-tunnel batching and mixing strategy, there are further capabilities for protecting against powerful attackers, such as allowing each step in a garlic routed path to define a delay or window in which it should be forwarded on. This would enable protections against the long term intersection attack, as a peer could send a message that looks perfectly standard to most peers that pass it along, except at any peers where the clove exposed includes delay instructions.
Performance related improvements are listed on the Performance page.