Cryptography – Particular algorithmic function encoding – Nbs/des algorithm
Patent
1995-01-12
1997-10-14
Cain, David C.
Cryptography
Particular algorithmic function encoding
Nbs/des algorithm
380 49, H04L 900
Patent
active
056779542
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a personal communication system for allowing a user to send and receive information with a user-intrinsic communication number at any communication terminal, and more particularly relates to a cryptical control method for encrypting communication information transmitted between the communication terminal and a switching station corresponding to a cryptical key.
RELATED ART
In a mobile communication system, communication information is easily received by a third party especially in a radio communication region. From this point of view, it has been proposed to encrypt communication information transmitted between a communication terminal (mobile radio terminal) and a switching station (connected to the mobile radio terminal through a base station) corresponding to a cryptical key. In other words, the communication terminal and the switching station that send and receive communication information to and from each other generate respective cryptical keys corresponding to communication-terminal-intrinsic information and encrypt the communication information transmitted therebetween corresponding to the cryptical keys.
In a personal communication, each user (subscriber) is assigned a user-intrinsic communication number (PID). The user uses the communication number to use a service. The user is charged for the use of the communication number. In the personal communication, the use can register a desired communication terminal corresponding to the user-intrinsic communication number so that he (she) can receive incoming communication at a his (her) convenient place. Every communication terminal has an intrinsic terminal identification number (SID). A database connected to the switching station records user communication numbers (PID) and the communication terminal identification number (SID) registered as receiving communication terminals. In the service network, conventional communication terminals that do not accord with the personal communication system are present. The conventional communication terminals are assigned communication numbers that are charged (namely, conventional telephone numbers) (PID). When a user initiates an outgoing communication, he or she should designate a communication number (PID) of a receiving user regardless of whether or not the receiving user is a subscriber of the personal communication. The switching station references the database and reads an identification number (SID) of a communication terminal corresponding to the designated communication number (PID), and connects the call to the communication terminal with the identification number. In the personal communication system, when two or more users register one communication terminal as their receiving terminals, they can share the communication terminal using their communication numbers (PID).
Now assume that a conventional cryptical control method is applied for the personal communication system so that a plurality of users can use the same communication terminal. In this case, when a cryptical key is generated to encrypt communication information transmitted between each user and the switching station, communication-terminal-intrinsic information is shared by the users. In other words, conventionally, communication-terminal-intrinsic information is provided as key generating information in secret. A cryptical key is generated corresponding to both a random number that is received from the switching station for each communication line and the terminal-intrinsic information. Corresponding to the cryptical key, communication information is encrypted. Thus, any user of the same communication terminal uses the same terminal-intrinsic information to generate a cryptical key that is used to encrypt the communication information. Thus, the cryptical reliability of communication information is deteriorated.
An object of the present invention is to provide a cryptical control method for personal communication that improves the cryptical reliability of communication information tra
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Hirata Shoichi
Tsukahara Hiroshi
Uchiyama Yasuyuki
Yabusaki Masami
Cain David C.
NTT Mobile Communications Network Inc.
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