پخش آفلاین از نظیر به نظیر با ناشناس بودن: | Offline Peer-to-Peer Broadcast with Anonymity:
Offline Peer-to-Peer Broadcast with Anonymity:
Content broadcasting is an effective method of delivering content to a large number of users.
Several products are now available to support live broadcasting in IP-based networks.
However, live broadcasting in a peer-to-peer (P2P) network involves a heavy concentrated communication load and incurs network delays that result in users not necessarily viewing a live transmission simultaneously.
In this paper we consider an alternative type of P2P broadcasting scheme, offline broadcasting, which provides a decentralized broadcasting service with anonymity.
This scheme provides a practical alternative to existing techniques for broadcasting content that can be created in advance.
We present security analysis of the scheme from the following aspects: security of our timed release encryption scheme, timed release capability, content plagiarism, masquerading, denial of service, and content protection.
Content broadcasting services are used for simultaneously distributing information to a great number of users.
A conventional broadcasting service requires a broadcasting server with huge computational resources and places a heavy burden on the network, which makes a broadcasting service costly.
We are seeing an increase in the significance of personal users as multimedia content providers.
For example, Consumer generated media (CGM) is a term that is increasingly used to describe multimedia content that is created by consumers and delivered over the Internet in relation to their own experience of products or services.
We have also seen the rise of YouTube  as a successful content distribution service for the likes of CGM.
Notably, YouTube provides for anonymous content distribution, which may be one of the reasons for its popularity since virtual identities are a widely used in Internet communities.
However, applications such as YouTube tend to adopt a centralized approach to content distribution, which does not suit all application environments.
The increasing importance of CGM raises the interesting question as to whether it is possible for personal users to advance from the open publication of multimedia content, which they can do already, to the provision of their own broadcasting services, which we term personal broadcasting.
From experience of existing applications such as YouTube, the capability to support anonymous broadcasting would seem a desirable property of any personal broadcasting application.
1-2 Peer-to-Peer Broadcasting:
Peer-to-peer (P2P) networks provide efficient decentralized platforms for distributing multimedia content.
Several network architectures have been proposed for P2P technology, for example Content-Addressable Network (CAN) , and Chord .
It has also been shown that a P2P network can reduce the overall cost to content providers in comparison with a content distribution scheme based on a centralized server .
A number of products to support live broadcast services in P2P networks are now available.
One example is PeerCast , which organizes user nodes into a hierarchical structure in order to enable efficient forwarding of streamed content.
Several other P2P live broadcasting schemes use a similar approach [8,9].
These schemes successfully use decentralization to reduce the heavy burden of providing a broadcasting service.
However, these live broadcasting schemes suffer from two problems.
Firstly, at the time of a live broadcast the network experiences a concentrated communication load as the live content stream is propagated throughout the community of nodes.
The network is further stressed if two or more nodes are simultaneously broadcasting.
Secondly, although these schemes aim to be efficient, it is unavoidable that there are delays in delivery of the broadcast content, with some nodes receiving it before others.
1-3 Offline Broadcasting:
In this paper, we propose an alternative approach to providing broadcasting services in a P2P network.
We refer to it as offline broadcasting since the content is distributed ahead of its start time, but users cannot view the content until a designated time.
While offline broadcasting cannot be used for live streaming, it does have the following properties:
1- nodes all have the capability to simultaneously access the content.
2- there is no communication congestion at the designated broadcast time.
3- broadcasters can create content anonymously.
Our offline broadcasting scheme does not require direct communication between the broadcasting server and users.
By predistributing the content, the heaviest burden of the scheme is temporally and spatially distributed amongst the users.
One way to implement an offline broadcasting scheme would be to distribute encrypted content in advance and then make the decryption key available at the broadcast start time.
However, if the broadcaster forwards this decryption the key at the start time then similar network delays to those for live broadcasting schemes will be experienced.
Alternatively, if the decryption key is released by a central key server then the complex issue of managing content-specific keys at the server end needs to be addressed.
We propose the use of a timed-release encryption scheme, which only requires the periodic broadcasting of time information.
In this way the offline broadcasting scheme requires no interaction between the broadcaster and users at the time of viewing.
With respect to anonymity, broadcasters can choose whether or not to link their identity to the content.