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Abstract

A method and apparatus for generating additional implicit keys from a key [K.sub.ij ].sub.N without the necessity of generating a new Diffie-Helman (DH) certificate or requiring communication between nodes to change implicit master keys is disclosed. A first data processing device (node I) is coupled to a private network which is in turn coupled to the Internet. A second data processing device (node J) is coupled to the same, or to a different network, which is also coupled to the Internet, such that node I communicates with node J using the Internet protocol. Node I is provided with a secret value i and a public value. Data packets (referred to as 'datagrams') are encrypted to enhance network security. Each node maintains an internal value of N which is incremented based on time and upon the receipt of a data packet from another node. The key [K.sub.ij ].sub.N.sbsb.i is derived from the appropriate quantity of .alpha..sup.Nij by using high order key-sized bits of the respective quantity. The present invention then utilizes the key [K.sub.ij ].sub.N.sbsb.i to encrypt a transient key which is referred to as K.sub.p. Node I encrypts the IP data in K.sub.p and encrypts K.sub.p in [K.sub.ij ].sub.N.sbsb.i. Node I transmits the encrypted IP datagram packet in the encrypted key K.sub.p to the receiving node J. Node I further includes its current internal value of N.sub.i in the outgoing packet. The present invention also provides for the application of one-way functions to the shared secret to enhance security. Thus, either node I or node J may change the context such that if in the future [K.sub.ij ].sub.N.sbsb.i is compromised, or is not useable by a cracker to either decrypt prior encrypted packets. The present invention discloses methods and apparatus for achieving perfect forward security for closed user groups, and for the application of the SKIP methodology to datagram multicast protocols.

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First Claim