System for decrypting encrypted software

• US 5,875,247 A
• Filed: 08/01/1995
• Issued: 02/23/1999
• Est. Priority Date: 09/09/1994
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakahara, Masaru, Itami, Satoshi, Utsumi, Kenichi, Nakashima, Kazuo
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US08/510,123
• Time in Patent Office: 1,302 Days
• Field of Search: 370/4, 370/20, 370/21, 370/23, 370/25, 370/44, 370/46, 370/49, 370/50, 370/29, 370/9
• US Class Current: 705/52
• CPC Class Codes: G06F 21/121 Restricting unauthorised execution of programs

Abstract

A CD-ROM stores encrypted software. When a user desires to decrypt and install this software, an approval preparatory key is generated by an installer. This approval preparatory key is generated based on time data. When the user informs a center of this approval preparatory key, the center calculates a difference between this approval preparatory key and a decrypting key and vends this calculated result to a user in the form of an approval key. When the user inputs this approval key to an installer, the installer generates a decrypting key by adding the approval preparatory key to the approval key. The installer decrypts the software by this decrypting key and installs the encrypted software into a personal computer system.

Claims

1. A system for decrypting encrypted software including a decrypting device for decrypting the encrypted software by use of a decrypting key and a management device for managing the decryption of the software, said system comprising:

first key generating means for generating a first key based on time data in said decrypting device;

second key generating means for generating a second key by executing a direct operation according to a first function with respect to the decrypting key and the first key in said management device;

decrypting key generating means for generating the decrypting key by executing a reverse operation according to the first function with respect to the second key in said decrypting device; and

decrypting means for decrypting the encrypted software by said decrypting key in said decrypting device.

2. A system for decrypting encrypted software according to claim 1, further comprising:

accounting means for imposing a running royalty of the software each instance said second key generating means generates the second key in said management device.

3. A system for decrypting encrypted software according to claim 2, further comprising:

installing means, provided in said decrypting device, for installing the software decrypted by said decrypting means into a storage device for an apparatus using the software connected to said decrypting device.

4. A system for decrypting encrypted software according to claim 3, wherein said accounting means does not impose the running royalty of the software even if said second key generating means regenerates the second key for decrypting the same software in case the software once installed in said storage device is deleted from said storage device.

5. A system for decrypting encrypted software according to claim 4, further comprising:

uninstalling means for deleting the software installed in said storage device, said uninstalling means provided in said decypting device.

6. A system for decrypting encrypted software according to claim 5, further comprising:

third key generating means for generating a third key for proving, in case said uninstalling means deletes the software from said storage device, this effect, said third key generating means provided in said decrypting device.

7. A system for decrypting encrypted software according to claim 6, wherein said third key generating means generates the third key by performing a second arithmetic operation on the second key.

8. A system for decrypting encrypted software according to claim 7, wherein in case said third key generating means generates the third key,

said second key generating means generates the second key by performing the first arithmetic operation on the decrypting key and the third key, and

said decrypting key generating means generates the decrypting key by performing a backward calculation of the first arithmetic operation on the third key and the second key.

9. A system for decrypting encrypted software according to claim 8, wherein said management device further includes a memory for memorizing all of the first key and the third key which have undergone the first arithmetic operation by said second key generating means, and

said second key generating means does not perform the first arithmetic operation on the first key or the third key that is memorized in said storage means.

10. A system for decrypting encrypted software according to claim 8, wherein said management device further includes a memory for memorizing the first key which have undergone the first arithmetic operation by said second key generating means and the number of instances with which the second key is generated, and said second key generating means executes the first and second arithmetic operations the above number of instances on the first key stored in said storage means, and generates the second key only in the case the third key coincides with the result of the execution.

11. A system for decrypting encrypted software according to claim 6 wherein the third key contains data about the number of instances with which the software is deleted from said storage means.

12. A system for decrypting encrypted software according to claim 4, further comprising:

means for setting the software installed in said storage device in an unusable state, said setting means provided in said decrypting device.

13. A system for decrypting encrypted software according to claim 1, further comprising:

installing means, provided in said decrypting device, for installing the software decrypted by said decrypting means into a storage device for an apparatus using the software connected to said decrypting device.

14. A system for decrypting encrypted software according to claim 1, wherein the first arithmetic operation is an arithmetic operation of calcutating a difference between the first key and the decrypting key.

15. A system for decrypting encrypted software according to claim 1, wherein the software is a program to be executed by a computer.

16. A system for decrypting encrypted software according to claim 15, wherein said decrypting device is incorporated into a computer for executing the program.

17. A decrypting device coupled to a management unit and for decrypting encrypted software, comprising:

first key generating means for generating a first key based on time data;

decrypting key generating means for generating a decrypting key by executing a reverse operation according to the first function with respect to the second key if the management unit receiving the first key generates the second key by executing a direct operation according to a first function with respect to the decrypting key and the first key; and

decrypting means for decrypting the encrypted software using the decrypting key.

18. A management device for outputting a decrypting key for decrypting encrypted software to a decrypting device, said management device comprising:

means for receiving a first key generated based on time data in said decrypting device;

second key generating means for generating a second key by executing a direct operation according to a first function with respect to the decrypting key and the first key; and

transmitting means for transmitting the second key to said decrypting device.

19. A system for decrypting encrypted software comprising:

a decrypting device to decrypt encrypted software, comprising a first key generation unit for generating a first key based on time data corresponding to an instance of installation of said encrypted software; and

a management device in communication with the decrypting device and managing the decryption of said encrypted software, comprising a second key generation unit generating a second key by subtracting values of each digit of said first key from corresponding values of each digit of a decrypting key, said decrypting device further comprising;

a decrypting key generating unit to generate the decrypting key by adding corresponding values of each digit of said first key and said second key in said decrypting device, and

a decrypting unit in communication with the management device and for decrypting the encrypted software by use of the decrypting key.

20. A decrypting device for decrypting encrypted software, comprising:

a first key generating unit to generate a first key based on time data corresponding to an instance of installation of said encrypted software;

a management unit to generate a second key by subtracting corresponding values of each digit of said first key and a decrypting key; and

a decrypting key generating unit, in communication with the first key generating unit and the management unit, to generate the decrypting key by adding values of each digit of said first key and corresponding values of said second key, said decrypting device to decrypt the encrypted software by use of said decrypting key.

21. A management device for outputting a decrypting key used to decrypt encrypted software, said management device comprising:

a first key generation device to generate a first key based on time data;

a second key generating unit to generate a second key by subtracting corresponding values of each digit of said first key and a decrypting key; and

a transmitting device, in communication with the first key generation device and the second key generating unit, to transmit the second key to a decrypting device.

22. A method of decrypting encrypted software, said method comprising the steps of:

generating a first key based on time data;

generating a second key by subtracting corresponding values of each digit of said first key and a decrypting key;

generating a decrypting key by adding values of each digit of said first key and corresponding values of said second key; and

decrypting the encrypted software by use of said decrypting key.

23. A method for outputting a decrypting key used to decrypt encrypted software, said method comprising the steps of:

generating a first key based on time data;

generating a second key by subtracting corresponding values of each digit of said first key and a decrypting key; and

transmitting the second key to a decrypting device.

24. A system for decrypting encrypted software upon initial software installation comprising:

a decrypting device decrypting the encrypted software and comprising;

an approval preparatory key generating unit to generate an approval preparatory key based on time data of said software installation,

a decrypting key generating unit to generate a decrypting key by adding corresponding values of each digit of said approval preparatory key and an approval key, and

a decrypting unit to decrypt the encrypted software by use of the decrypting key; and

a management device in communication with said decrypting device and managing the decryption of said encrypted software, said management device comprising an approval key generation unit to generate the approval key based on the approval preparatory key.

25. A system for decrypting encrypted software upon software reinstallation comprising:

a decrypting device to decrypt encrypted software comprising;

an approval preparatory key generating unit to generate an approval preparatory key based on time data of said software reinstallation,

a decrypting key generating unit for generating a new decrypting key adding corresponding values of each digit of said approval preparatory key and said approval key in said decrypting device; and

a decrypting unit for decrypting the encrypted software by use of the new decrypting key; and

a management device in communication with said decrypting device and managing the decryption of said encrypted software, said management device comprising an approval key generation unit to generate an approval key by subtracting corresponding values of each digit of said approval preparatory key from the corresponding values of each digit of a previously stored decrypting key.

26. A system for decrypting encrypted software upon initial software installation comprising:

a decrypting device to generate an approval preparatory key based on time data of said software installation, to generate a decrypting key by adding corresponding values of each digit of said approval preparatory key and an approval key, and to decrypt the encrypted software by use of the decrypting key; and

a management device in communication with said decrypting device and managing the decryption of said encrypted software, said management device to generate the approval key based on the approval preparatory key.

27. A method for decrypting encrypted software upon initial software installation comprising the steps of:

generating, by a decrypting device, a decrypting key by adding corresponding values of each digit of said approval preparatory key and an approval key, and decrypting the encrypted software by use of the decrypting key; and

managing, by a management device, the decryption of said encrypted software, and generating the approval key based on the approval preparatory key, said approval preparatory key generated based on time data.