Device and method for certifying reliability of public key, and program for same

A non-transitory computer readable medium encoded with a computer program which, when executed by a computer, causes certification of a reliability of a second public key PK2 which is a part of a second key pair generated in association with a first key pair consisting of a first private key and a first public key PK1, wherein the first private key and a generator of a cyclic group “G” are denoted as “a” and “g”, and a first public key PK1 is “a·g” and a second public key PK2 is “ax·g”, where “x” is an integer and “r” is a random number or pseudo-random number or a piece of data including the random number or pseudo-random number, the computer program comprising:

• program code for receiving a certification request requesting the certification of the reliability of the second public key PK2, the certification request including certification data,
• program code for calculating an equation PK2=xPK1 in response to the certification request, and
• program code for transmitting a result of the calculation as a response to the certification request,
• wherein the calculation comprises:
• inputting the r included in the certification data into a hash function to output the integer x, and
• calculating the equation using the integer x.

An apparatus for certifying a reliability of a second public key PK2 which is a part of a second key pair generated in association with a first key pair consisting of a first private key and a first public key PK1, the apparatus comprising:

• a processor, and
• memory,
• wherein the first private key and a generator of a cyclic group “G” are denoted as “a” and “g”, and a first public key PK1 is “a·g” and a second public key PK2 is “ax·g”, where “x” is an integer and “r” is a random number or pseudo-random number or a piece of data including the random number or pseudo-random number,
• wherein the apparatus is configured to:
• receive a certification request requesting the certification of the reliability of the second public key PK2, the certification request including certification data,
• calculate an equation PK2=xPK1 in response to the certification request, and
• transmit a result of the calculation as a response to the certification request,
• wherein the r is included in the certification data, and
• wherein the calculation comprises:
• inputting the r into a hash function to output the integer x, and
• calculating the equation using the integer x.

A method for certifying a reliability of a second identifier ID2 generated in association with a first identifier ID1, wherein a first integer and a generator of a cyclic group “G” are denoted as “a” and “g”, and the first identifier ID1 is “a·g” and the second identifier ID2 is “ax·g”, where “x” is an integer and “r” is a random number or pseudo-random number or a piece of data including the random number or pseudo-random number, the method comprising:

• receiving a certification request requesting a certification of the reliability of the second identifier ID2, the certification request including certification data,
• calculating an equation ID2=xID1 in response to the certification request, and
• transmitting a result of the calculation as a response to the certification request,
• wherein the calculation comprises:
• inputting the r included in the certification data into a hash function to output the integer x, and
• calculating the equation ID2 using the integer x.

A non-transitory computer readable medium encoded with a computer program which, when executed by a computer, causes certification of a reliability of a second identifier ID2 generated in association with a first identifier ID1, wherein a first integer and a generator of a cyclic group “G” are denoted as “a” and “g”, and the first identifier ID1 is “a·g” and the second identifier ID2 is “ax·g”, and where “x” is an integer and “r” is a random number or pseudo-random number or a piece of data including the random number or pseudo-random number, the method computer program comprising:

• program code for receiving a certification request requesting a certification of the reliability of the second identifier ID2, the certification request including certification data,
• program code for calculating an equation represented by an equation ID2=xID1 in response to the certification request, and
• program code for transmitting a result of the calculation as a response to the certification request,
• wherein the calculation comprises:
• inputting the r included in the certification data into a hash function to output the integer x, and
• calculating the equation using the integer x.

An apparatus for certifying a reliability of a second identifier ID2 generated in association with a first identifier ID1, the apparatus comprising:

• a processor, and
• memory,
• wherein a first integer and a generator of a cyclic group “G” are denoted as “a” and “g”, and the first identifier ID1 is “a·g” and the second identifier ID2 is “ax·g”,
• wherein “x” is in integer and “r” is a random number or pseudo-random number or a piece of data including the random number or pseudo-random number,
• wherein the apparatus is configured to:
• receive a certification request requesting a certification of the reliability of the second identifier ID2, the certification request including certification data,
• calculate an equation ID2=xID1 in response to the certification request, and
• transmit a result of the calculation as a response to the certification request, and
• wherein the calculation comprises:
• inputting the r included in the certification data into a hash function to output the integer x, and
• calculating the equation using the integer x.