Cryptographic key update management method and apparatus
First Claim
1. Apparatus for managing key updates in a logical key hierarchy, comprising:
- a communication interface operable for receiving at a cache, records generated by a key-hierarchy manager for members using the logical key hierarchy, wherein the records include key updates comprising an encrypted key corresponding to a node of the logical key hierarchy and encrypted using a key that corresponds to a descendant of that node, hierarchy-node information for both the encrypted and encrypting keys and key-version information for at least the encrypted key; and
a manager of the cache operable to consolidate the records into a key history tree, wherein the key history tree has the same structure as the logical key hierarchy, the manager storing at each node of the key history tree, for each encrypted key associated with the node, the most up-to-date version of the encrypted key and its version information with any earlier versions being discarded.
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Abstract
A method and apparatus is provided for consolidating cryptographic key updates, the consolidated update information enabling, for example, a returning member of a secure group who has been offline, to recover the current group key, at least in most cases. The unconsolidated key updates each comprise an encrypted key, corresponding to a node of a key hierarchy, that has been encrypted using a key which is a descendant of that node. The key updates are used to maintain a key tree with nodes in this tree corresponding to nodes in the key hierarchy. Each node of the key tree is used to store, for each encrypting key used in respect of the encrypted key associated with the node, the most up-to-date version of the encrypted key with any earlier versions being discarded. The key tree, or a subset of the tree, is then provided to group members.
31 Citations
21 Claims
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1. Apparatus for managing key updates in a logical key hierarchy, comprising:
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a communication interface operable for receiving at a cache, records generated by a key-hierarchy manager for members using the logical key hierarchy, wherein the records include key updates comprising an encrypted key corresponding to a node of the logical key hierarchy and encrypted using a key that corresponds to a descendant of that node, hierarchy-node information for both the encrypted and encrypting keys and key-version information for at least the encrypted key; and a manager of the cache operable to consolidate the records into a key history tree, wherein the key history tree has the same structure as the logical key hierarchy, the manager storing at each node of the key history tree, for each encrypted key associated with the node, the most up-to-date version of the encrypted key and its version information with any earlier versions being discarded. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A system comprising multiple apparatuses and a key-hierarchy manager for managing said key hierarchy in dependence on the addition or removal of members and for outputting key update records reflecting changes made to the key hierarchy;
- the apparatuses being configured in a multiple-level hierarchical arrangement comprising a first-level apparatus arranged to receive the records output by the key-hierarchy manager, and one or more lower levels of apparatuses each arranged to receive the key history tree, or a subset of key history tree, produced by a said apparatus at the next level up, the apparatuses at the lowest level of the hierarchical arrangement each being arranged to provide its key history tree, or a subset of its key history tree, to a respective sub-group of members;
the apparatuses at each level of said hierarchical arrangement, other than said first level, each being arranged to maintain its said key history tree only in respect of keys corresponding to the nodes of a respective predetermined sub-hierarchy of said key hierarchy and keys for the path from the head of this sub-hierarchy that terminates at the root of the key hierarchy.
- the apparatuses being configured in a multiple-level hierarchical arrangement comprising a first-level apparatus arranged to receive the records output by the key-hierarchy manager, and one or more lower levels of apparatuses each arranged to receive the key history tree, or a subset of key history tree, produced by a said apparatus at the next level up, the apparatuses at the lowest level of the hierarchical arrangement each being arranged to provide its key history tree, or a subset of its key history tree, to a respective sub-group of members;
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13. A method of consolidating key updates provided in records that a key-hierarchy manager generates for members using a key-hierarchy, each comprising an encrypted key corresponding to a node of the key hierarchy that is used by the members and encrypted using a key that corresponds to a descendant of that node, hierarchy-node information for both the encrypted and encrypting keys, and key-version information for at least the encrypted key;
- the method comprising a tree-maintenance step of maintaining in a computer, on the basis of said records, a key history tree with tree nodes corresponding to nodes in said key hierarchy, this tree-maintenance step comprising a sub-step of storing in association with each tree node of the key history tree, for each encrypting key used in respect of the encrypted key associated with the node, the most up-to-date version of the encrypted key and its version information with any earlier versions being discarded.
- View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
Specification