TERMINAL, METHOD, AND PROGRAM

1 . A terminal to be used by each of a plurality of participants participating in a predetermined platform, the terminal comprising:

a secure calculation unit that executes predetermined incentive processing according to content of an evaluation x by secure multi-party computation with another terminal connected via a communication network using a fragment [x] of the evaluation x for an evaluation target.

2 . The terminal according to claim 1 ,

wherein the incentive processing includes updating of reputations of the participants, and

the secure calculation unit, when a reputation of an evaluator who has performed the evaluation x is set as r t and a reputation of the evaluation target is set as r s , updates [r t ]<←f 1 ([r t ], [x]) and [r s ]←g 1 ([r s ], [x]) and the reputation r t and the reputation Is by the secure multi-party computation using a function f 1 that outputs an updated fragment [r t ] according to [a] the fragment [x] and a fragment [r t ] using the fragment [x] of the evaluation x and the fragment [r t ] of the reputation r t as inputs and a function g 1 that outputs an updated fragment [r s ] according to the fragment [x] and a fragment [r s ] using the fragment [x] of the evaluation x and the fragment [r s ] of the reputation r s as inputs.

3 . The terminal according to claim 2 ,

wherein the incentive processing includes disclosure of predetermined information z in a case where a value of the reputation is equal to or greater than a predetermined threshold a, and

the secure calculation unit, when a reputation of the participant is set as r, calculates [z×h(r, a)] by the secure multi-party computation using a function h(r, a) (where the function h(r, a) returns 1 when r is equal to or greater than a and returns 0 when r is less than a) and restores a result of the computation.

4 . The terminal according to claim 1 ,

wherein the incentive processing includes point granting to the participant who has performed the evaluation x, and

the secure calculation unit, when the participant who has performed the evaluation x is set as P i , a reputation of the participant P i is set as r i , and a current point of the participant P i is set as d i , calculates [d i ]←f 2 ([d i ], [x], [r i ]) by the secure multi-party computation using a function f 2 that outputs a fragment [d i ] of the granted point according to a fragment [r i ] and [a] the fragment [x] using the fragment [d i ] of the point d i , the fragment [r i ] of the reputation r i and the fragment [x] of the reputation x as inputs.

5 . The terminal according to claim 1 ,

wherein the incentive processing includes transaction control between participants, and

the secure calculation unit, when participants who conduct a transaction with each other are set as P a and P b , a fragment of a reputation of the participant P a is set as [r a ], and a fragment of a reputation of the participant P b is set as [r b ], calculates C ([r a ], [r b ]) by the secure multi-party computation using a function C that outputs a predetermined index value for controlling the transaction between the participant P a and the participant P b using the fragment [r a ] and the fragment [r b ] as inputs.

6 . A method to be executed by a terminal to be used by each of a plurality of participants participating in a predetermined platform, the method comprising:

executing a secure calculation procedure of executing predetermined incentive processing according to content of an evaluation x by secure multi-party computation with another terminal connected via a communication network using a fragment [x] of the evaluation x for an evaluation target.

7 . A computer-readable non-transitory recording medium storing computer-executable program instructions that when executed by a processor, by each of a plurality of participants participating in a predetermined platform, cause a terminal to:

execute a secure calculation procedure of executing predetermined incentive processing according to content of an evaluation x by secure multi-party computation with another terminal connected via a communication network using a fragment [x] of the evaluation x for an evaluation target.

8 . The terminal according to claim 2 ,

wherein the incentive processing includes point granting to the participant who has performed the evaluation x, and

the secure calculation unit, when the participant who has performed the evaluation x is set as P i , a reputation of the participant P i is set as r i , and a current point of the participant P i is set as d i , calculates [d i ]←f 2 ([d i ], [x], [r i ]) by the secure multi-party computation using a function f 2 that outputs a fragment [d i ] of the granted point according to a fragment [r i ] and the fragment [x] using the fragment [d i ] of the point d i , the fragment [r i ] of the reputation r i and the fragment [x] of the reputation x as inputs.

9 . The terminal according to claim 2 ,

wherein the incentive processing includes transaction control between participants, and

the secure calculation unit, when participants who conduct a transaction with each other are set as P a and P b , a fragment of a reputation of the participant P a is set as [a], and a fragment of a reputation of the participant P b is set as [r b ], calculates C ([r a ], [b]) by the secure multi-party computation using a function C that outputs a predetermined index value for controlling the transaction between the participant P a and the participant P b using the fragment [r a ] and the fragment [r b ] as inputs.

10 . The method according to claim 6 ,

wherein the incentive processing includes updating of reputations of the participants, and

the secure calculation procedure, when a reputation of an evaluator who has performed the evaluation x is set as r t and a reputation of the evaluation target is set as r s , updates [r t ]←f 1 ([r t ], [x]) and [r s ]←g 1 ([r s ], [x]) and the reputation r t and the reputation r s by the secure multi-party computation using a function f 1 that outputs an updated fragment [r t ] according to the fragment [x] and a fragment [r t ] using the fragment [x] of the evaluation x and the fragment [r t ] of the reputation r t as inputs and a function g 1 that outputs an updated fragment [r s ] according to the fragment [x] and a fragment [r s ] using the fragment [x] of the evaluation x and the fragment [r s ] of the reputation Is as inputs.

11 . The method according to claim 10 ,

wherein the incentive processing includes disclosure of predetermined information z in a case where a value of the reputation is equal to or greater than a predetermined threshold a, and

the secure calculation procedure, when a reputation of the participant is set as r, calculates [z×h(r, a)] by the secure multi-party computation using a function h(r, a) (where the function h(r, a) returns 1 when r is equal to or greater than a and returns 0 when r is less than a) and restores a result of the computation.

12 . The method according to claim 6 ,

wherein the incentive processing includes point granting to the participant who has performed the evaluation x, and

the secure calculation procedure, when the participant who has performed the evaluation x is set as P i , a reputation of the participant P i is set as r i , and a current point of the participant P i is set as d i , calculates [d i ]←f 2 ([d i ], [x], [r i ]) by the secure multi-party computation using a function f 2 that outputs a fragment [d i ] of the granted point according to a fragment [r i ] and the fragment [x] using the fragment [d i ] of the point d i , the fragment [r i ] of the reputation r i and the fragment [x] of the reputation x as inputs.

13 . The method according to claim 10 ,

wherein the incentive processing includes point granting to the participant who has performed the evaluation x, and

the secure calculation procedure, when the participant who has performed the evaluation x is set as P i , a reputation of the participant P i is set as r i , and a current point of the participant P i is set as d i , calculates [d i ]←f 2 ([d i ], [x], [r i ]) by the secure multi-party computation using a function f 2 that outputs a fragment [d i ] of the granted point according to a fragment [r i ] and the fragment [x] using the fragment [d i ] of the point d i , the fragment [r i ] of the reputation r i and the fragment [x] of the reputation x as inputs.

14 . The method according to claim 6 ,

wherein the incentive processing includes transaction control between participants, and

the secure calculation procedure, when participants who conduct a transaction with each other are set as P a and P b , a fragment of a reputation of the participant P a is set as [r a ], and a fragment of a reputation of the participant P b is set as [r b ], calculates C ([r a ], [n]) by the secure multi-party computation using a function C that outputs a predetermined index value for controlling the transaction between the participant P a and the participant P b using the fragment [r a ] and the fragment [r b ] as inputs.

15 . The method according to claim 10 ,

wherein the incentive processing includes transaction control between participants, and

the secure calculation procedure, when participants who conduct a transaction with each other are set as P a and P b , a fragment of a reputation of the participant P a is set as [r a ], and a fragment of a reputation of the participant P b is set as [b], calculates C ([r a ], [b]) by the secure multi-party computation using a function C that outputs a predetermined index value for controlling the transaction between the participant P a and the participant P b using the fragment [r a ] and the fragment [r b ] as inputs.

16 . The computer-readable non-transitory recording medium according to claim 7 ,

wherein the incentive processing includes updating of reputations of the participants, and

the secure calculation procedure, when a reputation of an evaluator who has performed the evaluation x is set as r t and a reputation of the evaluation target is set as r s , updates [r t ]←f 1 ([r t ], [x]) and [r s ]←g 1 ([r s ], [x]) and the reputation r t and the reputation Is by the secure multi-party computation using a function f 1 that outputs an updated fragment [r t ] according to the fragment [x] and a fragment [r t ] using the fragment [x] of the evaluation x and the fragment [r t ] of the reputation r t as inputs and a function g 1 that outputs an updated fragment [r s ] according to the fragment [x] and a fragment [r s ] using the fragment [x] of the evaluation x and the fragment [r s ] of the reputation Is as inputs.

17 . The computer-readable non-transitory recording medium according to claim 16 ,

wherein the incentive processing includes disclosure of predetermined information z in a case where a value of the reputation is equal to or greater than a predetermined threshold a, and

the secure calculation procedure, when a reputation of the participant is set as r, calculates [z×h(r, a)] by the secure multi-party computation using a function h(r, a) (where the function h(r, a) returns 1 when r is equal to or greater than a and returns 0 when r is less than a) and restores a result of the computation.

18 . The computer-readable non-transitory recording medium according to claim 7 ,

wherein the incentive processing includes point granting to the participant who has performed the evaluation x, and

the secure calculation procedure, when the participant who has performed the evaluation x is set as P i , a reputation of the participant P i is set as r i , and a current point of the participant P i is set as d i , calculates [d i ]←f 2 ([d i ], [x], [r i ]) by the secure multi-party computation using a function f 2 that outputs a fragment [d i ] of the granted point according to a fragment [r i ] and the fragment [x] using the fragment [d i ] of the point d i , the fragment [r i ] of the reputation r i and the fragment [x] of the reputation x as inputs.

19 . The computer-readable non-transitory recording medium according to claim 7 ,

wherein the incentive processing includes transaction control between participants, and

the secure calculation procedure, when participants who conduct a transaction with each other are set as P a and P b , a fragment of a reputation of the participant P a is set as [r a ], and a fragment of a reputation of the participant P b is set as [r b ], calculates C ([r a ], [r b ]) by the secure multi-party computation using a function C that outputs a predetermined index value for controlling the transaction between the participant P a and the participant P b using the fragment [r a ] and the fragment [r b ] as inputs.

20 . The computer-readable non-transitory recording medium according to claim 16 ,

wherein the incentive processing includes point granting to the participant who has performed the evaluation x, and

the secure calculation procedure, when the participant who has performed the evaluation x is set as P i , a reputation of the participant P i is set as r i , and a current point of the participant P i is set as d i , calculates [d i ]←f 2 ([d i ], [x], [r i ]) by the secure multi-party computation using a function f 2 that outputs a fragment [d i ] of the granted point according to a fragment [r i ] and the fragment [x] using the fragment [d i ] of the point d i , the fragment [r i ] of the reputation r i and the fragment [x] of the reputation x as inputs.