Patent ID: 7606369

Claim:
A process for secret transmission of a message by establishing a common cryptographic key for n subscribers using the Diffie-Hellman process, as recited in comprising: assigning the n subscribers respective leaves of a binary-structured tree which has a root, n leaves, is of depth [log 2n] and has tree nodes; for each one of the n subscribers, generating a respective secret, the respective secret being assigned to each one of the n leaves to which the one of the n subscribers is assigned; and establishing secrets consecutively in a direction of the root of said tree for all k nodes of said tree starting from the n leaves of said tree across an entire hierarchy of said tree, wherein two already known secrets are combined using the Diffie-Hellman process to form a new common secret, the new common secret being allocated to a common node so that the common cryptographic key for all n subscribers is allocated to a last one of tree nodes, the last one of the tree nodes being the root of said tree; adding a new subscriber to the n subscribers of said tree so that there are n+1 subscribers of said tree, the adding step including: adding two new leaves as successors to a selected one of the n leaves of said tree so that a new binary-structure tree has n+1 leaves and is of depth [log 2(n+1)]; assigning the one of the n subscribers to whom the selected one of the n leaves is assigned one of the two new leaves and assigning the new subscriber to another one of the two new leaves, the selected one of the n leaves becoming the common node for the two new leaves; and starting from the new leaves in the direction of the root of said tree, establishing new secrets only in those of the tree nodes which lie within a framework of said tree on a path from the two new leaves to the root of said tree.