Patent ID: 7725709

Claim:
A method in a transmitter for cryptographic synchronization of data packets, wherein said data packets are transmitted to a receiver using the Secure Real-Time Transport Protocol (SRTP) as defined in Internet Engineering Task Force (IETF) Request for Comments (RFC) 3711, said method comprising the steps of: receiving a data packet for transmission; performing SRTP processing on said data packet except for integrity transform; determining whether a packet sequence number for said data packet is evenly divisible by R, where R is an integer previously agreed to by said transmitter and said receiver; and, if the packet sequence number is not evenly divisible by R; completing SRTP processing on said data packet; and, transmitting said data packet to said receiver; if the packet sequence number is evenly divisible by R; computing and appending a message authentication code (MAC) to said data packet, wherein said MAC is a function of an SRTP key associated with said data packet and a transmitter roll-over counter (ROC) value, said transmitter ROC value corresponding to a counter in said transmitter that is incremented whenever a sequence number counter in said transmitter rolls over; appending said transmitter ROC value to said data packet; completing SRTP processing on said data packet; and, transmitting said data packet to said receiver.