Can Poisoning Peer to Peer Networks Work?

andrewchen writes "Can poisoning peer to peer networks really work? Business 2.0 picked up my research paper from Slashdot and wrote an article about it. In my paper, I argue that P2P networks may have an inherent "tipping point" that can be triggered without stopping 100% of the nodes on the network, using a model borrowed from biological systems. For those who think they have a technical solution to the problem, I outlined a few problems with the obvious solutions (moderation, etc.)."

Checksumming can work

[Pedrito]

I disagree with your suggestion that checksums can't work. A way they could work is as follows.

Create a website with logins for the users. Users of this web site can create lists of checksum for the files they create or have downloaded and verified as valid.

Other users can check any given user's list, and perhaps even post comments about the user's list, a form of moderation, if you will.

The validity of any single file on any random user's list would certainly be questionable, but some lists would become "trusted" by the community through trial and error. Others would be recognized as bogus and ignored.

Just a thought. Give me more than a few minutes and I might be able to come up with a better one.

Re:Obvious technical solution take 2

[Dooferlad]

eDonkey 2000 / http://www.sharereactor.com do this. The eDonkey network works by using links (as in clickable on web pages) that contain MD4 sums of the file + file size to let users know about files on the network. It does have some searching capabilities but they are limited. This is persumably fixed in the new Overnet project the guy is doing.

The files are all downloaded in segments from multiple sources, and you sometimes get bad segments, but they are only a fraction of the total file size so you don't really care.

You just plain can't poison eDonkey / Overnet - it won't work. It is also the only network that I would be tempted to use to distribute real content since it is guaranteed that the user will get what you want them to.

Use Limewire

[asv108]

The latest versions of limewire use hashes from a specification called HUGE that probably defeat this type of posioning attack. You can check out a recent interview with limewire team here [zeropaid.com]. Go here [limewire.org] if you want to download the code or check out the dev docs(Which are pretty outdated).

Fake Checksums

[nuggz]

Here is a file
Bobs_Song.mp3 5 M Hash -XXXXXXX
You don't know that I gave you the wrong hash till you're done.
It can only tell you that you have the wrong file, after you have it

Sharereactor and edonkey

[dotslash]

A P2P program call edonkey (don't laugh) has partially solved this problem.

In order to dowload a file, you can use a URI such as (ed2k://|file|The_Adventrues_Of_Pluto_Nash(2002).C D1.FTF.eDKDistro.Sharereactor.bin|559778352|1b153e 31f5fdbe829488989d04dda2b1|/ [ed2k]
). The URI contains the "local filename", size and SHA-1 hash. A companion web site [sharereactor.com] acts as a directory of URI's for popular content. The content is screened by the folks running the site. It has now reached the point where the "pirate" teams have accounts and post SHA-1 encoded URIs before releasing the content into the wild. Most edonkey users don't use the embedded search and instead use directories such as sharereactor.

Checksums and signatures work

[mikec]

Mr Chen apparently does not understand public key cryptography. Using a "web of trust" does in fact work.

The author writes

For the uninitiated, checksums work by examining a file and creating a string that "fingerprints" the data. It can be used in many situations, but the most common application is to verify that a file has been correctly transfered. The basic idea, in relation to P2P, is that every file on a user's computer is checksummed, and this checksum is then published to everyone else. Then, it may be possible to create a directory of "correct" checksums, to make sure you are actually downloading what you want. Although this idea works for newsgroups and some other centralized services, it does not with P2P. Basically, it comes down to the fact that you must trust whomever is actually doing the checksumming, or else they can just lie and publish false checksums. In the case of P2P networks, the checksumming is done by the same person you want to figure out if you can trust! As far as I know, this is an unresolvable problem.

This is not an unresolvable problem at all; this is where web of trust comes in. The basic idea is for the publisher to sign the checksum using his or her private key. Others can then verify the signature using the publishers public key. This allows me to verify, using only a few bytes of information, that a publisher named SecretAgent did indeed publish a file. If I know that SecretAgent has previously published a lot of "good" files, then the file is probably good. If I don't have any experience with SecretAgent, but I do know that PrivateBenji is trustworthy, and PrivateBenji vouches for SecretAgent, then the file is probably good.

The author fundamentally misunderstands webs of trust:

Another idea that is often proposed is moderation, specifically "webs of trust." That is, people keep lists of people they trust, and then they implicitly trust (often with diminishing degree) the people they trust, and so on. In the context of P2P, the each user would then receive a "trust rating," reflecting the number of people that trust them. However, this can also be defeated fairly easily, by creating groups of malicious users that trust each other - then, untrustworthy users may have high scores leading to problems in the future. This kind of fraud has happened on eBay, where people give themselves recommendations to mislead future partners.

A web of trust is not a "trust rating" ala eBay. A web of trust is a specific group of people who vouch for each other. Creating a malicious group of people who trust each other does not cause problems. (In fact, it can actually help.) If I trust A, based on experience, and if A trusts B, based on experience, then I can probably trust B. The fact that C, D, and E are malicious doesn't cause problems, because neither A nor B trusts them.

Overkill

[Cryogenes]

Distributed trust and peer review are fine and good but not even needed for the simple task at hand.

Look at the warez scene to see how it goes. A handful of release groups whose names are known to everybody who is even vaguely interested is sufficient to ensure supply. If these groups are attacked by fake releases (rarely happens) they can use hash keys as you suggest (some already do).

Websites like www.sharereactor.com also safeguard against fakes - another mechanism which is strong enough to defeat the entire problem by itself.

What I am saying is that distributed moderating à la slashdot will not evolve. Instead, we will have a handful of "authorities" - Web sites or public keys - that everyone trusts.

Note that authority - when not combined with power - is a Good Thing (TM).