Device and method for conditional authentication

A conditional authentication method of authenticating the authority of a user by verifying the legitimacy of proof data generated for proving the authority of the user and by determining whether or not conditions added to the authority of the user are satisfied, said method comprising the steps of:

• inputting authentication data;
• inputting control information which is for generation of said proof data;
• inputting proof support information which is generated by performing a predetermined computation beforehand for the control information for generation of said proof data and for authentication characteristic information;
• determining whether or not the control information for generation of said proof data satisfies specific conditions;
• calculating the proof data from said input in the case where the control information for generation of said proof data satisfies the specific conditions;
• and
• verifying that said proof data is based on the authentication characteristic information,
• wherein said authentication characteristic information is a decryption key in an asymmetric cryptosysytem utilizing a discrete logarithm problem on a finite group G.

An authenticating computer program product for use in a computer to authenticate the authority of a user which authentication is effected by verifying the legitimacy of proof data generated for proving the authority of the user and by determining whether or not conditions added to the authority of the user are satisfied, said authenticating computer program product being used for causing said computer to execute the steps of:

• inputting authentication data;
• inputting control information which is used for generation of said proof data;
• inputting proof support information which is generated by performing a predetermined computation beforehand for the control information for generation of said proof data and for authentication characteristic information;
• determining whether or not the control information for generation of the proof data satisfies specific conditions;
• calculating said proof data from said input in the case where the control information for generation of said proof data satisfies the specific conditions;
• and
• verifying that said proof data is generated based on the authentication characteristic information,
• wherein said authentication characteristic information is a decryption key in an asymmetric cryptosysytem utilizing a discrete logarithm problem on a finite group G.

An access control device which authenticates the user's access right to predetermined information processing resources by verifying the legitimacy of proof data generated by the user relative to authentication data, said access control device comprising:

• a first memory part that stores said authentication data;
• a second memory part that stores control information for generation of the proof data;
• a third memory part that stores proof support information, said proof support information being obtained by performing a predetermined computation from the control information for generation of the proof data and from authentication characteristic information;
• a proof data generation part that generates the proof data from the control information for generation of the proof data and from the authentication characteristic information only when the control information for generation of the proof data satisfies specific conditions;
• a verification part that verifies said proof data;
• and
• an access control part that permits the user to make access to the information processing resources in the case where the result of said verification is correct,
• said authentication characteristic information being a decryption key in an asymmetric cryptosysytem utilizing a discrete logarithm problem on a finite group G.

A program execution control device which authenticates the authority to execute a program by verifying the legitimacy of proof data generated by a user relative to authentication data, said program execution control device comprising:

• a first memory part that stores said authentication data;
• a second memory part that stores control information for generation of said proof data;
• a third memory part that stores proof support information, said proof support information being obtained by performing a predetermined computation from the control information for generation of the proof data and from authentication characteristic information;
• a proof data generation part that generates the proof data from the control information for generation of the proof data and from the authentication characteristic information only when the control information for generation of the proof data satisfies specific conditions;
• a verification part that verifies said proof data;
• and
• a control part that performs execution of the program in the case where the result of said verification is correct, said authentication characteristic information being a decryption key in an asymmetric cryptosysytem utilizing a
• discrete logarithm problem on a finite group G.