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Fingerprinting schemes are technical means to discourage people from illegally redistributing the digital data they have legally purchased. These schemes enable the original merchant to identify the original users of the digital data. Anonymous fingerprinting schemes allow a seller to fingerprint information sold to a user without knowing the identity of the user and without the seller seeing the fingerprinted copy. Finding a (redistributed) fingerprinted copy enables the seller to find out and prove to third party whose copy it was. The merchant does not need to be trusted either fordistribution or to associate a pseudonym with the identity of a buyer. The protocols for distribution and for traitor tracing described below are proven to work even if the merchant is not trusted. In addition, our scheme can prevent the collusion of merchant and registration center to make false-accusation to honest users.
Merchant distributes copies of the content legally to the seed buyers. Each fragment of the content contains a different segment of the fingerprint embedded into it. The segments have low pair-wise correlations.
They receive fingerprinted copies of the contents from the merchant that are used by the P2P distribution system to bootstrap the system. They can be either real or dummy buyers
In case of illegal re-distribution, it participates in the tracing protocol that is used to identify the illegal re-distributor(s).
KG is honest-but-curious, which can honestly perform the assigned tasks and return correct results. However, it will collect as many sensitive contents as possible.In system, the entity is responsible for the users’ enrollment. Meanwhile, it not only generates most part of system parameter, but also creates most part of secret key for each user(Buyer).
Admin holdes all the buyers and merchants.Admin gives the access permission to every buyers and merchants because admin identify the illegal users.Then admin holds the all merchants upload files and secrete key details.
Most fingerprinting systems can be classified in three categories, namely symmetric, asymmetric and anonymous schemes. In symmetric schemes, the merchant is the one who embeds the fingerprint into the content and forwards the result to the buyer; hence, the buyer cannot be formally accused of illegal re-distribution, since the merchant also had access to the fingerprinted content and could be responsible for the re-distribution.
In asymmetric fingerprinting, the merchant does not have access to the fingerprinted copy, but he can recover the fingerprint in case of illegal re-distribution and thereby identify the offending buyer. In anonymous fingerprinting, in addition to asymmetry, the buyer preserves her anonymity (privacy) and hence she cannot be linked to the purchase of a specific content, unless she participates in an illegal re-distribution.
The content is divided into several ordered fragments and each of them is embedded separately with a random binary sequence. The binary sequence for each fragment is called segment and the concatenation of all segments forms the whole fingerprint.The merchant distributes different copies to a reduced set of M seed buyers. The fingerprints of these buyers are such that their segments have low pair-wise correlations.
The buyers other than the seed ones engage on P2P transfers of the content in such a way that each new buyer obtains fragments from at least two other buyers. The total number of buyers is N _ M.The communication between peer buyers is anonymous through an onion routing-like protocol using a proxy.The fingerprint of each new buyer is built as a recombination of the segments of its parents.
Proxies know the pseudonyms of source and destination buyers and they have access to the symmetric keys used for encrypting the multimedia content.A transaction record is created by a transaction monitor to keep track of each transfer between peer buyers. These records do not contain the embedded fingerprints, but only an encrypted hash of them.The fingerprints’ hashes are encrypted in such a way that the private key of at least one parent is required for obtaining their cleartext.
The real identities of buyers are known only by the merchant. The transaction monitor records buyers’ pseudonyms.In case of illegal re-distribution, a search is required through the distribution graph. The search starts from the seed buyers and is directed by a correlation function between the traced fingerprint and the fingerprints of the tested buyers.
These tested buyers must co-operate with a tracing authority to compute the correlation between their fingerprint and the one extracted from the illegally re-distributed file. The fingerprints’ hashes recorded in the transaction monitor are enough to prevent buyers from cheating in this step. At each step of the traitor tracing protocol, the buyer with maximum correlation is chosen as the most likely ancestor of the illegal re-distributor. This criterion is mostly right, but some incorrect choices may occur during the search process, requiring the exhaustion of a subgraph and backtracking.The search ends when perfect correlation is found between the fingerprint of the tested buyer and that of the illegally re-distributed file. If a buyer refuses to take a correlation test, the hash recorded in the transaction monitor can be used as evidence against her.
The use of automatic recombined fingerprints has been recently suggested in the literature showing remarkable advantages: the fingerprints of buyers are unknown to the merchant (achieving anonymity) and fingerprint embedding is required only for a few seed buyers, whereas the other fingerprints are automatically obtained as a recombination of segments. However, the published system has some shortcomings: 1) it requires an expensive graph search in order to identify an illegal re-distributor, 2) some innocent buyers are requested to co-operate for tracing, and 3) the P2P distribution protocol requires honest proxies. This paper shows that the co-operation of honest buyers in traitor tracing entails several relevant drawbacks that can make the published system fail under some circumstances.