Abstract: To provide a centralized control system for defending and taking countermeasures against an illegal access. A network device 3 detects an illegal access packet P1 transmitted from an illegal accessor's terminal 6, and transfers an encapsulated packet P2 of the illegal access packet P1 to a data center 1. A control system 11 in the data center 1 analyzes the packet P2, encapsulates a response packet P4 from a decoy server 13 pretending to be a response from a target server to be attacked 5 to acquire a packet P3, and then transmits the packet P3 to the network device 3. The network device 3 decapsulates the packet P3 so as to extract a response packet P4, and transmits the response packet P4 to the illegal accessor's terminal 6. The illegal accessor's terminal 6, upon reception of the response packet P4, would believe that the response packet P4 should be transmitted from the server 5, and start to illegally access the decoy server 13.

Abstract: A cryptographic apparatus has an encryption/encapsulation processing section for encrypting plaintext data received from a plaintext network, referencing the predetermined correspondence between addresses and different cryptographic apparatus, setting a new header based on the cryptographic apparatus corresponding to the address set in the header of the plaintext data as encapsulation processing, and transmitting ciphertext data provided thereby to the ciphertext network of the same IP subnet as the plaintext network, and a decryption/decapsulation processing section for decrypting ciphertext data received from the ciphertext network into plaintext data, again setting a header based on the address set in the header of the plaintext data as decapsulation processing, and transmitting plaintext data provided thereby to the plaintext network of the same IP subnet as the ciphertext network.

Abstract: To provide a centralized control system for defending and taking countermeasures against an illegal access. A network device 3 detects an illegal access packet P1 transmitted from an illegal accessor's terminal 6, and transfers an encapsulated packet P2 of the illegal access packet P1 to a data center 1. A control system 11 in the data center 1 analyzes the packet P2, encapsulates a response packet P4 from a decoy server 13 pretending to be a response from a target server to be attacked 5 to acquire a packet P3, and then transmits the packet P3 to the network device 3. The network device 3 decapsulates the packet P3 so as to extract a response packet P4, and transmits the response packet P4 to the illegal accessor's terminal 6. The illegal accessor's terminal 6, upon reception of the response packet P4, would believe that the response packet P4 should be transmitted from the server 5, and start to illegally access the decoy server 13.

Abstract: A cryptographic communication system in which packet data between terminals is encrypted, and which can reduce the wait time in a decryption apparatus. In the cryptographic communication system in which packet data transmitted and received between terminals is encrypted by a transmitting-side cryptographic apparatus and is decrypted by a receiving-side decryption apparatus.