Encryption apparatus, cryptographic communication system, key recovery system, and storage medium

DETAILED DESCRIPTION OF THE INVENTION A preferred embodiment of the present invention will now be described.
In the following description, "key piece" implies shared key data; "key decryption" implies to decrypt an encrypted key piece; and "key recovery" implies to decrypt individual key pieces to obtain a key before sharing.
FIG.
1 is a block diagram showing the overall configuration of a cryptographic communication system according to an embodiment of the present invention.
This cryptographic communication system comprises a key recovery agent 3, certificate authority 2, and approver 4 to allow recovering a session key or user's private key in cryptographic communications between users 1a and 1b.
The users 1a, 1b, and 1c, key recovery agent 3, certificate authority 2, and approver 4 can communicate with each other via a network (e.
g.
, the Internet) made up of a public network.
FIG.
2 is a block diagram showing the hardware arrangement of an apparatus constructing the users 1a.
1b, and 1c, key recovery agent 3, certificate authority (key recovery center) 2, or approver 4.
An apparatus 11 made up of the users 1a, 1b, and 1c, key recovery agent 3, certificate authority 2, and approver 4 has a hardware computer system made up of a CPU 12, controller 13, memory 14, communication device 15, display 16, keyboard 17, printer 18, and data bus 19.
Of these components, the memory 14 includes both a so-called main memory (e.
g.
, a RAM) and a secondary memory (e.
g.
, a hard disk).
The functions to be performed by users 1a, 1b, and 1c, key recovery agent 3, the certificate authority 2, or approver 4 are implemented by programs loaded on the main memory and control of the CPU 12 based on these programs.
More specifically, the 1 users 1a, 1b, and 1c, key recovery agent 3, the certificate authority 2 and approver 4 have different software arrangements.
The detailed contents of the functions performed by a combination of hardware and software will be described later with reference to the operational descriptions and flow charts