Reputation System Fights P2P Junk

yeejiun writes "Many of the files that are shared on p2p networks tend to be junk. Organizations such as the RIAA and music labels regularly pollute these networks with nonsense files masquerading as real music/video files. These junk files make it difficult for users to find what they want on such p2p networks. Some researchers at Cornell University have developed a reputation system called Credence, that works on the Gnutella network, allowing users to tell the good files from the bad ones."

Comments

eDonkey

[mnemonic_]

Doesn't the eDonkey2000 network already have a system like this? Users identify fakes and report them, then the phony file information propagates throughout the network and the fake file dies.

Re:eDonkey

[mnemonic_]

Ah, found it: donkey-fakes. eMule automatically downloads the fakes list upon startup, and prevents the files from spreading.

Good summary

[kernel_dan]

For those of you that can't be bothered to RTFA, this system takes a profile of how you vote on files and matches you with other people who voted similarly. Thus, the spammers would see different ratings than 'normal users.'

rtfa, sucka.

[knowles420]

7. Can a group of spammers game the Credence algorithm by voting thumbs-up for each others' spam ?

No. The trustworthiness computation is designed to preclude such attacks.

8. What happens when a large number of spammers vote each others' spam up ? Can they fool the reputation system ?

No. Credence's reputation computation is similar to Google's PageRank, but is more general - every node computes a different rank based on its own votes. Reputation flows from a given good node along trust edges towards other nodes. Spammers can create tight cliques in which everyone votes on each others' spam, but the entire clique will be deemed untrustworthy. And if anyone in the spammer clique does a search, they will see each others' spam ranked high.

or, just do whatever you want.

Re:rtfa, sucka.

[PylonHead]

No, the pot smoker is right. Your brain is too small to absorb their goodness.

In their system there is no single "high reputation" metric. Everyone had a different reputation to each other. Three people, A, B and C. A may have a high reputation as far as B is concerned, but C thinks A has a low reputation.

They do this by grouping people who vote the same way. So you trust the people that vote like you do.

Assuming that you vote good files up and bad files down, you will be grouped with people who do the same. At some point, the spammers have to start voting differently than you do.. voting their spam up. This will distance them from your trust network, and cause you to value their opinion less.

Re:rtfa, sucka.

[xquark]

yes correct, and in-fact it can be taken one step further:

assume the system is able to determine symmetric groups.
that is groups that have totally (or near totally) different
voting directions, an example would be the honest group and
the spammers group.

if say the spammers vote something up, instead of the honest
group ignoring their rating, they can use the symmetric
properties between their group and the spammer's group to
re-enforce their vote (aka the credence) of the file in
question - in this case rate it down even further.

If the right restrictions were put in place such as the fact
that the symmetric effect will only effect files that have a
negative credence and not files that have a positive credence,
then various forms of collusion can be over come.

A lie can always be turned into a truth and a truth into a lie...

Arash Partow
__________________________________________________
Be one who knows what they don't know,
Instead of being one who knows not what they don't know,
Thinking they know everything about all things.
http://www.partow.net/

Re:Torrents can be bogus too.

[nunchux]

True... But a bogus torrent usually doesn't survive too long and certainly doesn't see too many seeders. If it's been up for a day or two you can be reasonably sure it's valid.

Also, even the "pirate" torrent sites are centralized and often even have administrators, sometimes even comment boards. If a torrent is bogus, someone will take it down. (Not that I've been to those sites, of course...)

Of course this could all be manipulated, but AFAIK it hasn't been yet by the powers-that-be... And I don't see why they'd bother, when a threatening letter is all it usually takes to take a torrent site down, and it would take considerably more effort than turning a bunch of scratchy mp3's loose on kazaa.

Re:Self-policing is needed

[Penguin]

Yeah, because 300 years certainly isn't enough for a word to be recognized...?

From http://www.etymonline.com/index.php?term=pirate :

"Meaning "one who takes another's work without permission" first recorded 1701"

Come on, the term is older than RMS!