A survey of key management for secure group communication <s> KEY MANAGEMENT ROLE <s> Many emerging applications on the Internet requiring group communication have varying security requirements. Significant strides have been made in achieving strong semantics and security guarantees within group environments. However, in existing solutions, the scope of available security policies is often limited. This paper presents Antigone, a framework that provides a suite of mechanisms from which flexible application security policies may be implemented. With Antigone, developers may choose a policy that best addresses their security and performance requirements. We describe the Antigone's mechanisms, consisting of a set of micro-protocols, and show how different security policies can be implemented using those mechanisms. We also present a performance study illustrating the security/performance tradeoffs that can be made using Antigone. <s> BIB001 </s> A survey of key management for secure group communication <s> KEY MANAGEMENT ROLE <s> Secure group communication is an increasingly popular research area having received much attention in recent years. The fundamental challenge revolves around secure and efcient group key management. While centralized methods are often appropriate for key distribution in large groups, many collaborative group settings require distributed key agreement techniques. This work investigates a novel approach to group key agreement by blending binary key trees with DiAEe-Hellman key exchange. The resultant protocol suite is very simple, secure and fault-tolerant. Moreover, its eAEciency surpasses that of prior art. <s> BIB002
Key management plays an important role enforcing access control on the group key (and consequently on the group communication). It supports the establishment and maintenance of key relationships between valid parties according to a security policy being enforced on the group BIB001 . It encompasses techniques and procedures that can carry out: -Providing member identification and authentication. Authentication is important in order to prevent an intruder from impersonating a legitimate group member. In addition, it is important to prevent attackers from impersonating key managers. Thus, authentication mechanisms must be used to allow an entity to verify whether another entity is really what it claims to be. -Access control. After a party has been identified, its join operation should be validated. Access control is performed in order to validate group members before giving them access to group communication 1 (the group key, in particular). -Generation, distribution and installation of key material. It is necessary to change the key at regular intervals to safeguard its secrecy  ]. Additional care must be taken when choosing a new key to guarantee key independence. Each key must be completely independent from any previous used and future keys, otherwise compromised keys may reveal other keys. The key secrecy can be extended to membership changes. When a group requires backward and forward secrecy BIB002 , the key must be changed for every membership change. Backward secrecy is used to prevent a new member from decoding messages exchanged before it joined the group. If a new key is distributed for the group when a new member joins, it is not able to decipher previous messages even if it has recorded earlier messages encrypted with the old key. Forward secrecy is used to prevent a leaving or expelled group member to continue accessing the group's communication (if it keeps receiving the messages). If the key is changed as soon as a member leaves, that member will not be able to decipher group messages encrypted with the new key. As multicast is being used for group transmission, it is generally assumed that multicast should also be used to rekey the group. 2 It is not reasonable to consider transmitting data using a scalable multicast communication and rekeying the members under a non-scalable peerto-peer communication. If the group has thousands of members, sending them a new key one by one would not be efficient. Although rekeying a group before the join of a new member is trivial, 3 rekeying the group after a member leaves it is far more complicated. The old key cannot be used to distribute a new one, because the leaving member knows the old key. A group key distributor must therefore provide other mechanisms to rekey the group using multicast messages while maintaining the highest level of security possible.