Data transmission system and data transmission method

• US 20060133617A1
• Filed: 12/21/2005
• Published: 06/22/2006
• Est. Priority Date: 12/21/2004
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Minamizawa, Takeaki
• Granted Patent: US 8,190,874 B2
• Time in Patent Office: Days
• US Class Current: 380/286
• CPC Class Codes: H04L 2209/805 Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04L 9/0894 Escrow, recovery or storing of secret information, e.g. secret key escrow or cryptographic key storage

Abstract

A data transmission system includes a server and a terminal which communicates with the server. The server includes a key storage unit, data encryption unit, key transmission unit, and server encrypted-data transmission unit. The key storage unit stores a plurality of keys to encrypt data. The data encryption unit generates a plurality of encrypted data by encrypting data with the plurality of keys stored in the key storage unit. The key transmission unit transmits in advance, to the terminal, one key to decrypt one of the encrypted data generated by the data encryption unit. The server encrypted-data transmission unit transmits, to the terminal, the encrypted data generated by the data encryption unit. The terminal includes a decryption unit which decrypts the encrypted data transmitted from the server with a key transmitted in advance from the server. A data transmission method, data transmission server, data reception terminal, and recording medium are also disclosed.

Claims

1. A data transmission system comprising:

a server; and

a terminal which communicates with said server,

said server comprising

key storage means for storing a plurality of keys to encrypt data,

encryption means for generating a plurality of encrypted data by encrypting data with the plurality of keys stored in said key storage means,

key transmission means for transmitting in advance, to said terminal, one key to decrypt one of the encrypted data generated by said encryption means, and

encrypted-data transmission means for transmitting, to said terminal, the encrypted data generated by said encryption means, and

said terminal comprising decryption means for decrypting the encrypted data transmitted from said server with a key transmitted in advance from said server.

2. A system according to claim 1, wherein said server further comprises transmission key determination means for determining a key to be transmitted by said key transmission means, in accordance with a user of said terminal.

3. A system according to claim 2, wherein said transmission key determination means determines one of the plurality of keys stored in said key storage means as a key to be transmitted by said key transmission means.

4. A system according to claim 2, wherein

said server further comprises key generation means for generating a key having a limited time during which said decryption means of said terminal can decrypt encrypted data, and

said transmission key determination means determines the key generated by said key generation means as a key to be transmitted by said key transmission means.

5. A system according to claim 4, wherein said key generation means generates a key having a limited period during which said decryption means can decrypt encrypted data.

6. A system according to claim 4, wherein said key generation means generates a key having a day of the week on which said decryption means can decrypt encrypted data.

7. A system according to claim 2, wherein

said encryption means concatenates encrypted data, adds, to a start of concatenated encrypted data, a header containing encrypted-data start information serving as information representing a start position of each encrypted data, and generates concatenated encrypted data,

said encrypted-data transmission means transmits the concatenated encrypted data generated by said encryption means, and

said decryption means decrypts, on the basis of the encrypted-data start information contained in the concatenated encrypted data, encrypted data corresponding to the key transmitted in advance from said server out of the encrypted data which are concatenated as the concatenated encrypted data.

8. A system according to claim 7, wherein

said transmission key determination means generates key valid encrypted data information representing, out of the encrypted data which are concatenated as the concatenated encrypted data, encrypted data which can be decrypted by said decryption means with the key transmitted in advance by said key transmission means,

said key transmission means transmits in advance, to said terminal, the key valid encrypted data information generated by said transmission key determination means, and

said decryption means decrypts, on the basis of the encrypted-data start information contained in the concatenated encrypted data and the key valid encrypted data information, the encrypted data corresponding to the key transmitted in advance from said server out of the encrypted data which are concatenated as the concatenated encrypted data.

9. A system according to claim 1, further comprising a transmission apparatus having one-way transmission means for transmitting, to said terminal by a one-way communication method, encrypted data transmitted from said encrypted-data transmission means of said server,

wherein said terminal further comprises data reception means for receiving the encrypted data transmitted by the one-way communication method by said one-way transmission means of said transmission apparatus.

10. A data transmission method comprising the steps of:

transmitting in advance, to a terminal, one key to decrypt encrypted data obtained by encrypting data;

generating a plurality of encrypted data by encrypting data with a plurality of keys;

transmitting the generated encrypted data to the terminal; and

decrypting the encrypted data by the terminal with the key transmitted in advance.

11. A data transmission server comprising:

key storage means for storing a plurality of keys to encrypt data;

encryption means for generating a plurality of encrypted data by encrypting data with the plurality of keys stored in said key storage means, concatenating the generated encrypted data, adding, to a start of concatenated encrypted data, a header containing encrypted-data start information serving as information representing a start position of each encrypted data, and generating concatenated encrypted data;

key transmission means for transmitting in advance one key to decrypt one of the encrypted data generated by said encryption means; and

encrypted-data transmission means for transmitting the concatenated encrypted data generated by said encryption means.

12. A server according to claim 11, further comprising key generation means for generating a key having a limited period during which encrypted data can be decrypted,

wherein said key transmission means transmits the key generated by said key generation means.

13. A data reception terminal comprising:

data reception means for receiving concatenated encrypted data obtained by concatenating a plurality of encrypted data prepared by encrypting data, and adding, to a start of concatenated encrypted data, a header containing encrypted-data start information serving as information representing a start position of each encrypted data;

key reception means for receiving one key transmitted in advance, the key being used to decrypt one of the encrypted data; and

decryption means for decrypting, on the basis of the encrypted-data start information contained in the received concatenated encrypted data, encrypted data corresponding to the received key out of the encrypted data which are concatenated as the concatenated encrypted data.

14. A recording medium which records a program for causing a computer to execute the processes of causing storage means to store a plurality of keys to encrypt data,

generating a plurality of encrypted data by encrypting data with the plurality of keys stored in the storage means, concatenating the generated encrypted data, adding, to a start of concatenated encrypted data, a header containing encrypted-data start information serving as information representing a start position of each encrypted data, and generating concatenated encrypted data,

transmitting in advance one key to decrypt one of the generated encrypted data, and

transmitting the generated concatenated encrypted data.

15. A medium according to claim 14, wherein the program further causes a computer to execute the processes of

generating a key having a limited period during which encrypted data can be decrypted, and

transmitting the generated key as the process of transmitting a key.