Abstract: A communication system, which performs communication using a transmission packet encrypted by an IP-SEC encrypting method, includes a first encrypting circuit that encrypts a transmission packet by an IP-SEC encrypting method, a second encrypting circuit that encrypt header data to be used to decode the transmission packet encrypted by the first encrypting circuit, and a transmitting circuit that transmit the transmission packet whose header is encrypted by the second encrypting circuit. The communication system further includes a first decoding circuit that decode the authentication data of the reception packet using information to be used to decode the authentication data recorded in the IP-SEC header of the transmission packet and a second decoding circuit that decodes the reception packet using the authentication data decoded by the first decoding circuit.

Abstract: A communication system, which performs communication using a transmission packet encrypted by an IP-SEC encrypting method, includes a first encrypting circuit that encrypts a transmission packet by an IP-SEC encrypting method, a second encrypting circuit that encrypt header data to be used to decode the transmission packet encrypted by the first encrypting circuit, and a transmitting circuit that transmit the transmission packet whose header is encrypted by the second encrypting circuit. The communication system further includes a first decoding circuit that decode the authentication data of the reception packet using information to be used to decode the authentication data recorded in the IP-SEC header of the transmission packet and a second decoding circuit that decodes the reception packet using the authentication data decoded by the first decoding circuit.

Abstract: A communication system, which performs communication using a transmission packet encrypted by an IP-SEC encrypting method, includes a first encrypting circuit that encrypts a transmission packet by an IP-SEC encrypting method, a second encrypting circuit that encrypt header data to be used to decode the transmission packet encrypted by the first encrypting circuit, and a transmitting circuit that transmit the transmission packet whose header is encrypted by the second encrypting circuit. The communication system further includes a first decoding circuit that decode the authentication data of the reception packet using information to be used to decode the authentication data recorded in the IP-SEC header of the transmission packet and a second decoding circuit that decodes the reception packet using the authentication data decoded by the first decoding circuit.

Abstract: A communication system, which performs communication using a transmission packet encrypted by an IP-SEC encrypting method, includes a first encrypting circuit that encrypts a transmission packet by an IP-SEC encrypting method, a second encrypting circuit that encrypt header data to be used to decode the transmission packet encrypted by the first encrypting circuit, and a transmitting circuit that transmit the transmission packet whose header is encrypted by the second encrypting circuit. The communication system further includes a first decoding circuit that decode the authentication data of the reception packet using information to be used to decode the authentication data recorded in the IP-SEC header of the transmission packet and a second decoding circuit that decodes the reception packet using the authentication data decoded by the first decoding circuit.

Abstract: A communication system, which performs communication using a transmission packet encrypted by an IP-SEC encrypting method, includes a first encrypting circuit that encrypts a transmission packet by an IP-SEC encrypting method, a second encrypting circuit that encrypt header data to be used to decode the transmission packet encrypted by the first encrypting circuit, and a transmitting circuit that transmit the transmission packet whose header is encrypted by the second encrypting circuit. The communication system further includes a first decoding circuit that decode the authentication data of the reception packet using information to be used to decode the authentication data recorded in the IP-SEC header of the transmission packet and a second decoding circuit that decodes the reception packet using the authentication data decoded by the first decoding circuit.

Abstract: A communication system, which performs communication using a transmission packet encrypted by an IP-SEC encrypting method, includes a first encrypting circuit that encrypts a transmission packet by an IP-SEC encrypting method, a second encrypting circuit that encrypt header data to be used to decode the transmission packet encrypted by the first encrypting circuit, and a transmitting circuit that transmit the transmission packet whose header is encrypted by the second encrypting circuit. The communication system further includes a first decoding circuit that decode the authentication data of the reception packet using information to be used to decode the authentication data recorded in the IP-SEC header of the transmission packet and a second decoding circuit that decodes the reception packet using the authentication data decoded by the first decoding circuit.

Abstract: To prevent cell-delay-variation of ATM cells to be transmitted and to compress numeral data without increasing CPU load, an ATM data controller for controlling data exchange between a data processing system and an ATM interface comprises a first FIFO (3) for buffering transmission data supplied from and received data to be supplied to the data processing system, a third FIFO (7) for buffering transmission ATM cells and received ATM cells, and a second FIFO (5) for buffering transmission cell data to be assembled into the transmission ATM cells and received cell data obtained by disassembling the received ATM cells. When the transmission data is numeral data, a data compressing/decompressing means (4) compresses the transmission data by deleting upper four bits of every byte of the transmission data, and an ATM interface control section (6) sets a data-compression flag in the cell-header.