Signature calculation system by use of mobile agent

• US 20010016911A1
• Filed: 01/17/2001
• Published: 08/23/2001
• Est. Priority Date: 01/18/2000
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Obana, Satoshi
• Granted Patent: US 7,103,775 B2
• Time in Patent Office: Days
• US Class Current: 713/180
• CPC Class Codes: H04L 2209/80 Wireless
• CPC Class Codes: H04L 9/3255 using group based signatures, e.g. ring or threshold signatures

Abstract

A signature calculation system includes: a mobile agent for calculating a digital signature of the owner of the mobile agent; a base host of the mobile agent from which the mobile agent starts moving in a network; and remote hosts in the network which can be visited by the mobile agent. In the base host in which the mobile agent is activated, a secret key #0 of the owner of the mobile agent is partitioned and distributed into cipher texts (partial signature auxiliary data) that can be restored only when calculations by use of secret keys of k remote hosts are executed, and data including the cipher texts are stored in the mobile agent. A remote host visited by the mobile agent arbitrarily presents signature target data. If the mobile agent determined to write a digital signature for the signature target data, the mobile agent stores the signature target data and moves to the next remote host. Thereafter, each remote host visited by the mobile agent calculates a partial signature by use of the data stored in the mobile agent and a secret key of the remote host. After the mobile agent visited k remote hosts since the presentation of the signature target data, the mobile agent returns to the remote host that presented the signature target data, at which the digital signature for the signature target data by use of the secret key of the owner of the mobile agent is obtained from the partial signatures calculated by the k remote hosts.

Claims

1. A signature calculation system by use of a mobile agent, comprising:

a mobile agent for calculating a digital signature of the owner of the mobile agent;

a base host of the mobile agent from which the mobile agent starts moving in a network; and

remote hosts in the network which can be visited by the mobile agent, wherein;

the base host includes;

an agent execution environment for letting the mobile agent execute its program code;

a random number generation means for generating random numbers;

a partial signature auxiliary data generation means to which the random numbers generated by the random number generation means and a secret key of the owner of the mobile agent are inputted and which generates partial signature auxiliary data for distributing the information of the secret key of the owner of the mobile agent to the remote hosts so that the partial signature auxiliary data will be used when partial signatures necessary for the calculation of the digital signature of the owner of the mobile agent are calculated by remote hosts; and

a public key cryptography calculation means for conducting encryption and signature calculation for the partial signature auxiliary data generated by the partial signature auxiliary data generation means, and

each remote host includes;

an agent execution environment for letting the mobile agent execute its program code;

a partial signature calculation means to which signature target data, data which have been carried by the mobile agent and a secret key of the remote host are inputted and which calculates a partial signature which is necessary for the calculation of the digital signature of the owner of the mobile agent;

a partial signature combining means to which one or more partial signatures calculated by one or more remote hosts are inputted and which outputs the digital signature calculated for the signature target data by use of the secret key of the owner of the mobile agent; and

a public key cryptography calculation means for conducting encryption and signature calculation for the partial signature calculated by the partial signature calculation means, and

the mobile agent, which started from the base host carrying the partial signature auxiliary data and which is arbitrarily presented with the signature target data by a remote host, stores the signature target data if the mobile agent determined to write the digital signature for the signature target data by use of the secret key of the owner of the mobile agent, and thereafter visits k (k;

security parameter) remote hosts and carries the partial signatures calculated by the remote hosts to the remote host that presented the signature target data, at which the digital signature for the signature target data by use of the secret key of the owner of the mobile agent is obtained from the partial signatures calculated by the k remote hosts.

2. A signature calculation system by use of a mobile agent as claimed in

claim 1

, wherein one or more components of the remote host selected from the partial signature calculation means, the partial signature combining means and the public key cryptography calculation means are implemented by program code of the mobile agent.

3. A signature calculation system by use of a mobile agent as claimed in

claim 1

, wherein the partial signature auxiliary data generated by the partial signature auxiliary data generation means include cipher texts (G_i, M_i) (1≦

i<

k) which are obtained by encrypting random numbers r_i (1≦

i<

k) that satisfy a predetermined relationship with the secret key of owner of the mobile agent by use of ElGamal cryptosystem public keys y_i (1≦

i<

k).

4. A signature calculation system by use of a mobile agent as claimed in

claim 3

, wherein signatures calculated for the random numbers r_i (1≦

i<

k) by use of the secret key of the owner of the mobile agent are added to the partial signature auxiliary data carried by the mobile agent.

5. A signature calculation system by use of a mobile agent as claimed in

claim 1

, wherein the digital signature calculated for the signature target data is an RSA digital signature.

6. A signature calculation system by use of a mobile agent as claimed in

claim 5

, wherein the partial signature combining means of the remote host that presented the signature target data calculates the digital signature for the signature target data by obtaining the product (mod p×

q (p, q;

prime number of approximately 512 bits)) of the partial signatures calculated by the k remote hosts.

7. A signature calculation system by use of a mobile agent, comprising:

a mobile agent for calculating a digital signature of the owner of the mobile agent;

a base host of the mobile agent from which the mobile agent starts moving in a network; and

remote hosts in the network which can be visited by the mobile agent, wherein;

the base host includes;

an agent execution environment for letting the mobile agent execute its program code;

a random number generation means for generating random numbers;

a partial signature auxiliary data generation means to which the random numbers generated by the random number generation means are inputted and which generates a new secret key and a new public key corresponding to the newly generated secret key and generates partial signature auxiliary data for distributing the information of the newly generated secret key to the remote hosts so that the partial signature auxiliary data will be used when partial signatures necessary for the calculation of the digital signature of the owner of the mobile agent are calculated by remote hosts; and

a public key cryptography calculation means for conducting encryption and signature calculation for the partial signature auxiliary data generated by the partial signature auxiliary data generation means, and

each remote host includes;

an agent execution environment for letting the mobile agent execute its program code;

a partial signature calculation means to which signature target data, data which have been carried by the mobile agent and a secret key of the remote host are inputted and which calculates a partial signature which is necessary for the calculation of the digital signature of the owner of the mobile agent;

a partial signature combining means to which one or more partial signatures calculated by one or more remote hosts are inputted and which outputs the digital signature calculated for the signature target data by use of the newly generated secret key; and

a public key cryptography calculation means for conducting encryption and signature calculation for the partial signature calculated by the partial signature calculation means, and

the mobile agent, which started from the base host carrying the partial signature auxiliary data and which is arbitrarily presented with the signature target data by a remote host, stores the signature target data if the mobile agent determined to write the digital signature for the signature target data by use of the newly generated secret key, and thereafter visits k (k;

security parameter) remote hosts and carries the partial signatures calculated by the remote hosts to the remote host that presented the signature target data, at which the digital signature for the signature target data by use of the newly generated secret key is obtained from the partial signatures calculated by the k remote hosts.

8. A signature calculation system by use of a mobile agent as claimed in

claim 7

, wherein one or more components of the remote host selected from the partial signature calculation means, the partial signature combining means and the public key cryptography calculation means are implemented by program code of the mobile agent.

9. A signature calculation system by use of a mobile agent as claimed in

claim 7

, wherein the partial signature auxiliary data generated by the partial signature auxiliary data generation means include cipher texts (G_i, M_i) (1≦

i<

k) which are obtained by encrypting random numbers r_i (1≦

i<

k) that satisfy a predetermined relationship with the newly generated secret key by use of ElGamal cryptosystem public keys y_i (1≦

i<

k).

10. A signature calculation system by use of a mobile agent as claimed in

claim 9

, wherein signatures calculated for the random numbers r_i (1≦

i<

k) by use of a secret key of the owner of the mobile agent, a signature calculated for the newly generated public key by use of the secret key of the owner of the mobile agent, and the newly generated public key are added to the partial signature auxiliary data carried by the mobile agent.

11. A signature calculation system by use of a mobile agent as claimed in

claim 7

, wherein the digital signature calculated for the signature target data is an RSA digital signature.

12. A signature calculation system by use of a mobile agent as claimed in

claim 11

, wherein the partial signature combining means of the remote host that presented the signature target data calculates the digital signature for the signature target data by obtaining the product (mod p×

q (p, q;

prime number of approximately 512 bits)) of the partial signatures calculated by the k remote hosts.

13. A computer-readable record medium storing a program for instructing a computer of a base host of a mobile agent to execute:

an agent execution process for letting the mobile agent execute its program code;

a random number generation process for generating random numbers;

a partial signature auxiliary data generation process for receiving the random numbers generated in the random number generation process and a secret key of the owner of the mobile agent as input data and generating partial signature auxiliary data for distributing the information of the secret key of the owner of the mobile agent to remote hosts so that the partial signature auxiliary data will be used when partial signatures necessary for the calculation of a digital signature of the owner of the mobile agent are calculated by remote hosts; and

a public key cryptography calculation process for conducting encryption and signature calculation for the partial signature auxiliary data generated in the partial signature auxiliary data generation process.

14. A computer-readable record medium storing a program for instructing a computer of a remote host to execute:

an agent execution process for letting a mobile agent execute its program code;

a partial signature calculation process for receiving signature target data which has been arbitrarily presented to the mobile agent by a remote host, data which have been carried by the mobile agent, and a secret key of the remote host as input data, and calculating a partial signature which is necessary for the calculation of a digital signature of the owner of the mobile agent for the signature target data;

a partial signature combining process for receiving one or more partial signatures calculated by one or more remote hosts as input data and outputting the digital signature calculated for the signature target data by use of a secret key of the owner of the mobile agent; and

a public key cryptography calculation process for conducting encryption and signature calculation for the partial signature calculated in the partial signature calculation process.

15. A computer-readable record medium as claimed in

claim 14

, wherein the digital signature calculated for the signature target data in the partial signature combining process is an RSA digital signature.

16. A computer-readable record medium as claimed in

claim 15

, wherein in the partial signature combining process, the digital signature for the signature target data is calculated by obtaining the product (mod p×

q (p, q;

prime number of approximately 512 bits)) of the partial signatures calculated by the one or more remote hosts.

17. A computer-readable record medium storing a program for instructing a computer of a base host of a mobile agent to execute:

an agent execution process for letting the mobile agent execute its program code;

a random number generation process for generating random numbers;

a partial signature auxiliary data generation process for receiving the random numbers generated in the random number generation process as input data, generating a new secret key and a new public key corresponding to the newly generated secret key, and generating partial signature auxiliary data for distributing the information of the newly generated secret key to remote hosts so that the partial signature auxiliary data will be used when partial signatures necessary for the calculation of a digital signature of the owner of the mobile agent are calculated by remote hosts; and

a public key cryptography calculation process for conducting encryption and signature calculation for the partial signature auxiliary data generated in the partial signature auxiliary data generation process.

18. A computer-readable record medium storing a program for instructing a computer of a remote host to execute:

an agent execution process for letting a mobile agent execute its program code;

a partial signature calculation process for receiving signature target data which has been arbitrarily presented to the mobile agent by a remote host, data which have been carried by the mobile agent, and a secret key of the remote host as input data, and calculating a partial signature which is necessary for the calculation of a digital signature of the owner of the mobile agent for the signature target data;

a partial signature combining process for receiving one or more partial signatures calculated by one or more remote hosts as input data and outputting the digital signature calculated for the signature target data by use of the newly generated secret key; and

a public key cryptography calculation process for conducting encryption and signature calculation for the partial signature calculated in the partial signature calculation process.

19. A computer-readable record medium as claimed in

claim 18

, wherein the digital signature calculated for the signature target data in the partial signature combining process is an RSA digital signature.

20. A computer-readable record medium as claimed in

claim 19

, wherein in the partial signature combining process, the digital signature for the signature target data is calculated by obtaining the product (mod p×

q (p, q;

prime number of approximately 512 bits)) of the partial signatures calculated by the one or more remote hosts.