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Multicast is what enables a node on a network to address one unit of data to a specific group of receivers.〔Micciancio, Daniele and Saurabh Panjwani. (“Multicast Encryption: How to maintain secrecy in large, dynamic groups?” )〕 In interactive multicast at the data link or network layer, such as IP multicast, Ethernet multicast or MBMS service over cellular network, receivers may join and leave the group using an interaction channel. Only one copy of the data is sent from the source, and multiple copies are created and then sent to the desired recipient by the network infrastructure nodes.〔 In for example IP multicast, a multicast group is identified by a class D IP address. A host enters or exits a group using IGMP (Internet Group Management Protocol).〔 A message sent via multicast is sent to all nodes on the network, but only the intended nodes accept the multicast frames.〔Pessi, Pekka. Department of Computer Science, Helsinki University Of Technology. (“Secure Multicast” ).〕 Multicasting is useful in situations such as video conferencing and online gaming.〔 Multicast was used originally in LANs, with Ethernet being the best example.〔 A problem with multicast communication is that it is difficult to guarantee that only designated receivers receive the data being sent. This is largely because multicast groups are always changing; users come and go at any time. A solution to the problem of ensuring that only the chosen recipient obtains the data is known as multicast encryption.〔 ==ISO Standards== The ISO (International Organization for Standardization) states that confidentiality, integrity, authentication, access control, and non-repudiation should all be considered when creating any secure system.〔 * Confidentiality: No unauthorized party can access appropriate messages. * Integrity: Messages cannot be changed during transit without being discovered. * Authentication: The message needs to be sent by the person/machine who claims to have sent it. * Access control: Only those users enabled can access the data. * Non-repudiation: The receiver can prove that the sender actually sent the message.〔 To be secure, members who are just being added to the group must be restricted from viewing past data. Also, members removed from a group may not access future data.〔Pannetrat, Alain and Refik Molva. (“Multiple Layer Encryption for Multicast Groups” ).〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Multicast encryption」の詳細全文を読む スポンサード リンク
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