Decryption key management scheme for software distribution system

Claims

What is claimed is:

1. A method for managing a decryption key for decrypting an encrypted software to be installed into a computer using a software distribution system in which the decryption key is obtained in exchange for a payment of a software usage charge, and the encrypted software is obtained without the payment of the software usage charge, comprising the steps of:

searching the decryption key in a memory device of said computer, the memory device including a software content memory unit for storing a software content of each currently installed software and a decryption key memory unit for storing each decryption key for decrypting each previously installed and subsequently deleted software;

acquiring the decryption key from a distribution source of the encrypted software in exchange for the payment of the software usage charge when the decryption key is not found in the memory device by the searching step;

decrypting the encrypted software by using the decryption key obtained at the searching step or the acquiring step, installing a decrypted software content of the encrypted software into the software content memory unit of the memory device, and storing the decryption key into the software content memory unit of the memory device; and

deleting the encrypted software by deleting the decrypted software content installed at the decrypting step and the decryption key stored at the decrypting step from the software content memory unit of the memory device, and storing the decryption key into the decryption key memory unit of the memory device, such that the decryption key stored in the decryption key memory unit of the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software without requiring another payment of the software usage charge.

2. The method of claim 1, wherein the storing step stores the decryption key separately from the decrypted software content in the memory device.

3. The method of claim 1, wherein the storing step stores the decryption key in a memory medium separately provided from a memory medium for installing the decrypted software content in the memory device.

4. The method of claim 1, further comprising the step of:

deleting a previously installed software by deleting a decrypted software content of the previously installed software from the memory device, while maintaining a decryption key for decrypting the previously installed software in the memory device.

5. A method for distributing a software from a distribution source to users using a software distribution system in which the decryption key is obtained in exchange for a payment of a software usage charge, and the encrypted software is obtained without the payment of the software usage charge, comprising the steps of:

encrypting software to be distributed to users at a distribution source side, and distributing encrypted software to users;

searching a decryption key for decrypting the encrypted software in a memory device of a user's computer at an individual user side, the memory device including a software content memory unit for storing a software content of each currently installed software and a decryption key memory unit for storing each decryption key for decrypting each previously installed and subsequently deleted software;

providing the decryption key corresponding to the encrypted software from the distribution source side to the individual user side in exchange for the payment of the software usage charge when the decryption key is not found in the memory device by the searching step;

decrypting the encrypted software distributed at the encrypting step by using the decryption key obtained at the searching step or the providing step, installing a decrypted software content of the encrypted software into the software content memory unit of the memory device, and storing the decryption key into the software content memory unit of the memory device at the individual user side; and

deleting the encrypted software by deleting the decrypted software content installed at the decrypting step and the decryption key stored at the decrypting step from the software content memory unit of the memory device, and storing the decryption key into the decryption key memory unit of the memory device at the individual user side, such that the decryption key stored in the decryption key memory unit of the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software without requiring another payment of the software usage charge.

6. The method of claim 5, wherein the providing step includes the steps of:

requesting the decryption key from the individual user side to the distribution source side;

carrying out at the distribution source side a processing for charging a software usage charge to a user who requested the decryption key at the requesting step; and

sending the decryption key from the distribution source side to the individual user side of said user in exchange for a payment of the software usage charge by said user.

7. The method of claim 1, wherein the storing step stores the decryption key in correspondence to a software ID of the encrypted software, and the searching step searches the decryption key by using the software ID acquired from the encrypted software.

8. The method of claim 1, wherein the acquiring step acquires the decryption key by a communication with the distribution source through a communication network.

9. The method of claim 1, further comprising the step of:

acquiring the encrypted software by a communication between said computer and the distribution source through a communication network.

10. The method of claim 1, further comprising the step of:

acquiring the encrypted software by obtaining a memory medium which stores an encrypted software content and which is distributed by the distribution source, and setting the memory medium in said computer.

11. The method of claim 1, wherein the searching step, the acquiring step, the decrypting step, and the storing step are executed by non-encrypted installer programs accompanying the encrypted software.

12. The method of claim 1, wherein the searching step, the acquiring step, the decrypting step, and the storing step are executed by installer programs implemented in said computer in advance.

13. A computer for managing a decryption key for decrypting an encrypted software to be installed into said computer using a software distribution system in which the decryption key is obtained in exchange for a payment of a software usage charge, and the encrypted software is obtained without the payment of the software usage charge, comprising:

a memory device including a software content memory unit for storing a software content of each currently installed software, and a decryption key memory unit for storing each decryption key for decrypting each previously installed and subsequently deleted software;

a decryption key retrieval unit for retrieving the decryption key for decrypting the encrypted software from the memory device;

a decryption key acquisition unit for acquiring the decryption key corresponding to the encrypted software from a distribution source of the encrypted software in exchange for the payment of the software usage charge when the decryption key is not found in the memory device by the decryption key retrieval unit;

a decryption and install unit for decrypting the encrypted software by using the decryption key obtained by the decryption key retrieval unit or the decryption key acquisition unit, installing a decrypted software content of the encrypted software into the software content memory unit of

the memory device, and storing the decryption key into the software content memory unit of the memory device; and

a decryption key storing unit for deleting the encrypted software by deleting the decrypted software content installed at the decrypting step and the decryption key stored at the decrypting step from the software content memory unit of the memory device, and storing the decryption key into the decryption key memory unit of the memory device, such that the decryption key stored in the decryption key memory unit of the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software without requiring another payment of the software usage charge.

14. The computer of claim 13, wherein the decryption key storing means stores the decryption key separately from the decrypted software content in the memory device.

15. The computer of claim 13, wherein the decryption key storing means stores the decryption key in a memory medium separately provided from a memory medium for installing the decrypted software content in the memory device.

16. The computer of claim 13, further comprising:

means for deleting a previously installed software by deleting a decrypted software content of the previously installed software from the memory device, while maintaining a decryption key for decrypting the previously installed software in the memory device.

17. A system for distributing a software from a distribution source to users using a software distribution system in which the decryption key is obtained in exchange for a payment of a software usage charge, and the encrypted software is obtained without the payment of the software usage charge, comprising:

a distribution source computer center for encrypting software to be distributed to users, and distributing encrypted software to users; and

a plurality of user's computers connected with the distribution source computer center via a communication network, each user's computer having:

a memory device including a software content memory unit for storing a software content of each currently installed software, and a decryption key memory unit for storing each decryption key for decrypting each previously installed and subsequently deleted software;

a decryption key retrieval unit for retrieving the decryption key for decrypting the encrypted software from the memory device;

a decryption key acquisition unit for acquiring the decryption key corresponding to the encrypted software from the distribution source computer center in exchange for the payment of the software usage charge when the decryption key is not found in the memory device by the decryption key retrieval unit;

a decryption and install unit for decrypting the encrypted software distributed by the distribution source computer center by using the decryption key obtained by the decryption key retrieval unit or the decryption key acquisition unit, installing a decrypted software content of the encrypted software into the software content memory unit of the memory device, and storing the decryption key into the software content memory unit of the memory device; and

a decryption key storing unit for deleting the encrypted software by deleting the decrypted software content installed at the decrypting step and the decryption key stored at the decrypting step from the software content memory unit of the memory device, and storing the decryption key into the decryption key memory unit of the memory device, such that the decryption key stored in the decryption key memory unit of the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software without requiring another payment of the software usage charge.

18. The system of claim 17, wherein the distribution source computer center carries out a processing for charging a software usage charge to a user who requested the decryption key, and sends the decryption key to the user's computer of said user in exchange for a payment of the software usage charge by said user.

19. The computer of claim 13, wherein the decryption key storing means stores the decryption key in correspondence to a software ID of the encrypted software, and the decryption key retrieval means retrieves the decryption key by using the software ID acquired from the encrypted software.

20. The computer of claim 13, wherein the decryption key acquisition means acquires the decryption key by a communication with the distribution source through a communication network.

21. The computer of claim 13, further comprising:

means for acquiring the encrypted software by a communication between said computer and the distribution source through a communication network.

22. The computer of claim 13, further comprising:

means for setting the encrypted software in said computer, the encrypted software being provided as a memory medium which stores an encrypted software content and which is distributed by the distribution source.

23. The computer of claim 13, wherein the encrypted software is accompanied by non-encrypted installer programs for controlling operations of the decryption key retrieval means, the decryption key acquisition means, the decryption and install means, and the decryption key storing means.

24. The computer of claim 13, further comprising:

installer programs implemented in said computer in advance for controlling operations of the decryption key retrieval means, the decryption key acquisition means, the decryption and install means, and the decryption key storing means.

25. A computer usable medium having computer readable program code stored therein for causing a computer to function as a system for managing a decryption key for decrypting an encrypted software to be installed into said computer using a software distribution system in which the decryption key is obtained in exchange for a payment of a software usage charge, and the encrypted software is obtained without the payment of the software usage charge, the computer readable program code comprising:

first computer readable program code for causing said computer to search the decryption key in a memory device of said computer, the memory device including a software content memory unit for storing a software content of each currently installed software and a decryption key memory unit for storing each decryption key for decrypting each previously installed and subsequently deleted software;

second computer readable program code for causing said computer to acquire the decryption key from a distribution source of the encrypted software in exchange for the payment of the software usage charge when the decryption key is not found in the memory device by the first computer readable program code;

third computer readable program code for causing said computer to decrypt the encrypted software by using the decryption key obtained by the first computer readable program code or the second computer readable program code, install a decrypted software content of the encrypted software into the software content memory unit of the memory device, and storing the decryption key into the software content memory unit of the memory device; and

fourth computer readable program for causing said computer to delete the encrypted software by deleting the decrypted software content installed by the third computer readable program code and the decryption key stored by the third computer readable program code from the software content memory unit of the memory device, and store the decryption key into the decryption key memory unit of the memory device, such that the decryption key stored in the decryption key memory unit of the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software without requiring another payment of the software usage charge.

26. The article of claim 25, wherein the fourth computer readable program code means causes said computer to store the decryption key separately from the decrypted software content in the memory device.

27. The article of claim 25, wherein the fourth computer readable program code means causes said computer to store the decryption key in a memory medium separately provided from a memory medium for installing the decrypted software content in the memory device.

28. The article of claim 25, further comprising:

fifth computer readable program code means for causing said computer to delete a previously installed software by deleting a decrypted software content of the previously installed software from the memory device, while maintaining a decryption key for decrypting the previously installed software in the memory device.

29. The article of claim 25, wherein the computer usable medium contains the encrypted software and the computer readable program code means which are not encrypted, and the computer usable medium is distributed by the distribution source and used by being set in said computer.

30. The article of claim 25, wherein the computer usable medium is implemented in said computer in advance.

31. The article of claim 25, wherein the fourth computer readable program code means causes said computer to store the decryption key in correspondence to a software ID of the encrypted software, and the first computer readable program code means causes said computer to search the decryption key by using the software ID acquired from the encrypted software.

32. The article of claim 25, wherein the second computer readable program code means causes said computer to acquire the decryption key by a communication with the distribution source through a communication network.

33. The article of claim 25, further comprising:

eighth computer readable program code means for causing said computer to acquire the encrypted software by a communication between said computer and the distribution source through a communication network.

34. The article of claim 25, further comprising:

ninth computer readable program code means for causing said computer to set the encrypted software in said computer, the encrypted software being provided as a memory medium which stores an encrypted software content and which is distributed by the distribution source.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a decryption key management scheme for managing a decryption key for decrypting an encrypted software in a software distribution system.

2. Description of the Background Art

Conventionally, a software to be used by a computer is individually stored in a recording medium such as floppy disks and usually sold at a retail store in a form of a software package which contains the recording medium along with a manual and other necessary items.

In a case of such a software package, the licensing to give a permission to use the software is usually made in a form which is inseparable from the sale of the software package. For instance, there are cases in which a document describing that a contract to use the software is established as soon as the software package is opened is distributed along with the software package itself, or cases in which a user is required to sign a contract to use the software with the software vender by using a user registration form enclosed in the software package.

In contrast, recently, there are propositions for a new software distribution scheme aimed at realization of a freer distribution style and a tighter software right owner protection. As a representative example of such a new software distribution scheme, the so called superdistribution scheme is well known (see: R. Mori and M. Kawahara, "Superdistribution: The Concept and the Architecture", The Transactions of the IEICE, Vol. E73, No. 7, pp. 1133-1146, July 1990; and U.S. Pat. No. 5,103,392).

The superdistribution scheme utilizes a software structure formed by an encrypted software content and a header portion having a function to decrypt the encrypted software content. In addition, two concepts called "S-credit" and "Software Usage Monitor" are utilized to realize the licensing between a user and a software right owner and the management of software usage charges.

"S-credit" is realized in a form of a memory card such as an IC card which stores information as to quantitatively how much software usage is to be permitted to a user. A user who wishes to use the software distributed by the superdistribution first pays an appropriate fee at a service center of the superdistribution system, and receives the "S-credit" which registers the information corresponding to the paid fee.

"Software Usage Monitor" is a program which recognizes a balance of the user's contract from a value of the information registered in the "S-credit", and permits or prohibits the execution of the software according to the recognized balance of the user's contract. This program permits the execution of the software after confirming the availability of the "S-credit" indicating a balance greater than a certain value on the computer, and decreases the value of the information registered in the "S-credit" (indicating the balance) as much as a fee to be charged for this software.

However, in such a method for managing the software usage charges using "S-credit", there is a need to provide a protection against illegal copying of "S-credit" or illegal rewriting of data of "S-credit", and to this end, it has been necessary to use a specialized hardware mechanism for limiting read/write with respect to "S-credit", for example.

For this reason, recently, there is a proposition for a new software distribution system in which the encrypted software content is distributed to users for free or for a very small charge, and a key for decrypting the encrypted software content is issued to a user who wishes to use this software in exchange for the payment of the software usage charge.

In this software distribution system, the software vender can save costs required for production and distribution of individual software packages, and in addition, an effective means for advertising the software can be provided by packaging a non-encrypted demonstration version of this software for demonstrating the encrypted software content in a medium such as CD-ROM which stores the encrypted software content. From a viewpoint of a user, this feature can provide an advantage in that there is a chance to try and see if the software is worth purchasing before actually purchasing the software.

The user receives the decryption key in exchange for the payment of the software usage charge for a desired software, and installs this software into a hard disk device of his own computer by decrypting the encrypted software content using the received decryption key.

In this manner, the software distribution system utilizing the decryption key can manage the software usage charge in a form of the exchange of the decryption key, so that there is no need for "S-credit" and a specialized hardware for managing "S-credit" required by the superdistribution scheme, and therefore it is possible to realize a freer software distribution style.

Now, considering a usual manner by which a user uses a computer, it often becomes necessary to delete the already installed software once in order to increase a usable capacity of the hard disk device, and then re-install the same software back to the hard disk device later on when a need to use this software arises. In a case of using the usual non-encrypted, packaged software, the user still possesses the recording medium contained in the software package itself, so that the deletion of the installed software on the hard disk device causes no problem, because it is possible to re-install the software from the recording medium when this software becomes necessary later on.

In contrast, in a case of the above described software distribution system utilizing the decryption key, the decrypted software which was installed on the hard disk device by using the decryption key is the only executable software available for a user. Consequently, when the user loses the decryption key which was acquired from the software vender in exchange for the software usage charge and wishes to re-install the same software, it is necessary to acquire the decryption key by paying the software usage charge for the same software again. This fact can lead to a lower reliability of the software distribution system utilizing the decryption key, which in turn can present a hindrance to a spread of this software distribution system utilizing the decryption key.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a decryption key management scheme for a software distribution system utilizing the decryption key, which can enable the re-install of the software that was decrypted once by a proper procedure, without requiring a re-acquisition of the decryption key from the software vender, so that a user can freely delete and re-install the software that was properly obtained once.

According to one aspect of the present invention there is provided a method for managing a decryption key for decrypting an encrypted software to be installed into a computer, comprising the steps of: searching the decryption key in a memory device of said computer; acquiring the decryption key from a distribution source of the encrypted software when the decryption key is not found in the memory means by the searching step; decrypting the encrypted software by using the decryption key obtained at the searching step or the acquiring step, and installing a decrypted software content into the memory device; and storing the decryption key acquired by the acquiring step into the memory device, such that the decryption key stored in the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software.

According to another aspect of the present invention there is provided a computer for managing a decryption key for decrypting an encrypted software to be installed into said computer, comprising: a memory device for storing a software content of each currently installed software, and a decryption key for decrypting each previously installed software; decryption key retrieval means for retrieving the decryption key for decrypting the encrypted software from the memory device; decryption key acquisition means for acquiring the decryption key corresponding to the encrypted software from a distribution source of the encrypted software when the decryption key is not found in the memory means by the decryption key retrieval means; decryption and install means for decrypting the encrypted software by using the decryption key obtained by the decryption key retrieval means or the decryption key acquisition means, and installing a decrypted software content into the memory device; and decryption key storing means for storing the decryption key acquired by the decryption key acquisition means into the memory device, such that the decryption key stored in the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software.

According to another aspect of the present invention there is provided an article of manufacture, comprising: a computer usable medium having computer readable program code means embodied therein for causing a computer to function as a system for managing a decryption key for decrypting an encrypted software to be installed into said computer, the computer readable program code means including: first computer readable program code means for causing said computer to search the decryption key in a memory device of said computer; second computer readable program code means for causing said computer to acquire the decryption key from a distribution source of the encrypted software when the decryption key is not found in the memory means by the first computer readable program code means; third computer readable program code means for causing said computer to decrypt the encrypted software by using the decryption key obtained by the first computer readable program code means or the second computer readable program code means, and install a decrypted software content into the memory device; and fourth computer readable program code means for causing said computer to store the decryption key acquired by the second computer readable program code means into the memory device, such that the decryption key stored in the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software.

According to another aspect of the present invention there is provided a method for distributing a software from a distribution source to users, comprising the steps of: encrypting a software to be distributed to users at a distribution source side, and distributing an encrypted software to users; searching a decryption key for decrypting the encrypted software in a memory device of a user's computer at an individual user side; providing the decryption key corresponding to the encrypted software from the distribution source side to the individual user side when the decryption key is not found in the memory means by the searching step; decrypting the encrypted software distributed at the encrypting step by using the decryption key obtained at the searching step or the providing step, and installing the decrypted software content into the memory device at the individual user side; and storing the decryption key acquired by the acquiring step into the memory device at the individual user side, such that the decryption key stored in the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software.

According to another aspect of the present invention there is provided a system for distributing a software from a distribution source to users, comprising: a distribution source computer center for encrypting a software to be distributed to users, and distributing an encrypted software to users; and a plurality of user's computers connected with the distribution source computer center via a communication network, each user's computer having: a memory device for storing a software content of each currently installed software, and a decryption key for decrypting each previously installed software; decryption key retrieval means for retrieving the decryption key for decrypting the encrypted software from the memory device; decryption key acquisition means for acquiring the decryption key corresponding to the encrypted software from the distribution source computer center when the decryption key is not found in the memory means by the decryption key retrieval means; decryption and install means for decrypting the encrypted software distributed by the distribution source computer center by using the decryption key obtained by the decryption key retrieval means or the decryption key acquisition means, and installing a decrypted software content into the memory device; and decryption key storing means for storing the decryption key acquired by the decryption key acquisition means into the memory device, such that the decryption key stored in the memory device is utilizable in decrypting the encrypted software at a time of re-installing the encrypted software.

Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of one embodiment of a software distribution system according to the present invention.

FIG. 2 is a diagram showing a program structure of an installer in an encrypted software used in the system of FIG. 1.

FIG. 3 is a diagram illustrating functions to be realized by programs included in the installer shown in FIG. 2.

FIG. 4 is a diagram showing a data structure of a decryption key request message used in the system of FIG. 1.

FIG. 5 is a diagram showing an operation of a software vender side in a case of receiving the decryption key request message of FIG. 4.

FIG. 6 is a diagram showing an alternative configuration using a common installer for all encrypted softwa