Cryptography – Key management – Key distribution
Reexamination Certificate
1998-06-30
2001-09-25
Swann, Tod (Department: 2132)
Cryptography
Key management
Key distribution
C380S273000, C713S163000
Reexamination Certificate
active
06295361
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to networking and, specifically, to a method and apparatus allowing a key manager node in a network to initiate a process of changing a group key for multiple members of a group in the network.
Internet Protocol (IP) multicasting is useful for disseminating data to a large group of receivers in a network. Multicasting of data is a form of network communication in which a transmitting node (a “sender”) sends the data via a single message to multiple destinations at once. The multiple destinations are the recipients (“receivers”) of the message. Other methods of network communication include broadcast, in which a sender transmits to all possible recipients, and unicast, in which the sender transmits only to one specific recipient. Multicast is described in more detail in T. A. Maufer,
Deploying IP Multicast in the Enterprise,
Prentice Hall PTR, 1998, which is herein incorporated by reference in its entirety to the extent that it does not conflict with the invention as described herein. A multicast sender may send a message to a selected group of receivers in a multicast group. A multicast group includes at least one sender that transmits data to nodes on a particular multicast address. A multicast group also includes one or more receivers. A receiver is a node that listens on a particular address in the network. Receivers become members of the group because they are interested in receiving messages. A node may be both a sender and a receiver of data to and from other nodes.
In certain conventional multicast systems, a sender distributes a group key to all nodes in the multicast group. Each member in the multicast group receives the same group key. This group key may be used by the one or more senders to encrypt data and by the receivers to decrypt the data sent to the group or to decrypt other, individual keys sent to the group members. When a member leaves a group or is no longer trusted, it is necessary to change the group key so that the former member will not be able to decrypt information encrypted with the group key. It is also wise for the sender to change the group key periodically in case the key has been compromised. It is also wise to change the group key if enough time has passed since the group key was last distributed that the group key could be compromised.
Some conventional multicasting systems, such as the “Enclave” system developed by Li Gong (as described in L. Gong, “Enclaves: Enabling Secure Collaboration over the Internet”. IEEE Journal on Selected Areas in Communications, 15(3):567-575, April 1997) allow the sender to distribute a new key (encrypted separately for each member) directly via multicasting. Unfortunately, this method does not scale to large numbers of members, since the amount of data multicast to all members grows as the number of members grows.
As another example, the SKIP (Simple Key Management for Internet Protocols) protocol distributes keys that are deemed valid for a certain predetermined time period and updates these keys by a unicast. This distribution method causes a problem when a member leaves the group, since the member still has access to the group key until that group key expires. SKIP does not allow for quick key change when a member leaves the group or is suspected to be compromised.
SUMMARY OF THE INVENTION
Described embodiments of the present invention allow a key manager node in a network to initiate the process of changing a group key for all nodes in a multicasting group. A “key manager” is the network entity in charge of key distribution and management. In the described embodiment, the key manager node initiates changing the group key by setting an indicator (called a “key change indicator”) in a multicast packet. The key change indicator indicates that each of the nodes in the multicast group should obtain the new group key. The key manager sets the indicator whenever the key manager determines that the nodes in the group need to change their key. The members in the multicast group then obtain the new group key from the key manager via an appropriate key distribution process.
Various embodiments use one of several methods described herein to perform key distribution. In certain embodiments, the group members individually request a new group key. In other embodiments, the key manager transmits the key to the group members using another appropriate mechanism. In one embodiment of the present invention, the key manager distributes the group key to the members of the group in response to a request from each member. Once all group members have received the new group key (or a timeout has occurred), the key manager sends an indicator that the group members should start using the new group key. In another embodiment, the key manager sends the new group key to the group members, along with instructions specifying when the new key is to take effect. For example, the new key can take effect at a certain time or for all received packets having a packet number higher than a certain packet number. In another embodiment, each receiver in the group uses both the new group key and the old group key for a predetermined time period or until all group members have received the key, while each sender in the group receives an indication from the key manager that it should switch to the new group key. In still other embodiments, the key manager unicasts or multicasts the new group key to the group members without receiving a request.
Various embodiments implement the key change indicator in different ways. As discussed above, the key change indicator can be a flag formed of one or more bits in a packet. The key change indicator can also be an indicator in the data, such as a control character. The key change indicator can also be a separate type of packet or message. Similarly, the indicator that the group should start using the new key, which is used in certain embodiments, can also be a flag, a control character, a type of packet or message, or any other appropriate type of indicator.
The group key used in the described embodiments of the present invention is a shared secret key, as is known to persons of ordinary skill in the art. An example of such a shared secret key encryption method is the DES encryption method.
In accordance with the purpose of the invention, as embodied and broadly described herein, the invention relates to at least a method of changing a group key, comprising the steps performed by a node including a key manager function in a system for processing data, of: sending an indicator to each member of a group that it is time to change the group key; and distributing a new group key to at least one member of the group.
In further accordance with the purpose of the invention, as embodied and broadly described herein, the invention relates to a method of changing a group key, comprising the steps performed by a system for processing data, of: sending, by a key manager node, an indicator to each member of a group that it is time to change the group key; and distributing, by the key manager node, a new group key to at least one member of the group.
In further accordance with the purpose of the invention, as embodied and broadly described herein, the invention relates to method of changing a group key, comprising the steps performed by a member of a group in a system for processing data, of: receiving, by the member of the group, an indicator that it is time to change the group key; sending, by the member of the group, in response to the indicator, a request for a new group key; and receiving, after the sending step, the new group key.
Advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims and equivalents.
REFERENCES:
patent: 5748736 (1998-05-01), Mittra
patent: 60498
Hanna Stephen R.
Kadansky Miriam C.
Smithers Matthew
Squire Sanders & Dempsey LLP
Sun Microsystems Inc.
Swann Tod
LandOfFree
Method and apparatus for multicast indication of group key... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for multicast indication of group key..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for multicast indication of group key... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2468069