Patent ID: 7426636

Claim:
A method of providing compact secure data communication, the method comprising the computer-implemented steps of: receiving from a sender over a non-secure data communication network, a data packet comprising a security parameter index value, an explicit sequence value, a compressed encrypted payload, and a first authentication tag value; estimating an implicit sequence value based on the explicit sequence value; determining whether the packet has been replayed, based on the implicit sequence value; when the packet has not been replayed; decrypting the compressed encrypted payload to yield an uncompressed payload; applying the uncompressed payload and implicit sequence number to an authentication function; and accepting the data packet when a second authentication tag value generated by the authentication function matches the first authentication tag value, wherein the estimating step comprises the steps of: for the explicit sequence value E, estimating the implicit sequence value as a value I defined by I=2 16 *A+E, where A is selected from a set {R−1, R, R+1} such that I is closest to a value 2 16 *R+S; wherein S represents a prior explicit sequence value; wherein a rollover value R counts a number of times that S has incremented to its maximum value (2 16 =65,535) and rolled over to zero; wherein if the value of R is zero, then I is estimated as E; wherein if the value of R is 2 48 −1, then I is estimated as I=2 16 *(R−1)+E.