Detection system, detection method, and detection program

1 . A detection system comprising:

a node; and

a verification server, wherein

the node includes first processing circuitry configured to:

generate a plurality of random values based on a seed received from the verification server, and

generate a response based on information on an area of a first storage content specified by the plurality of generated random values, and transmit the generated response to the verification server, and

the verification server includes second processing circuitry configured to:

generate a plurality of random values based on the seed,

generate a verification response based on information on an area of a second storage content specified by the plurality of generated random values,

determine whether the response received from the node matches the verification response, and

output a determination result,

wherein the first processing circuitry is further configured to execute processing of gradually narrowing a range that a next random value can take, each time a random value is generated, to preemptively exclude invalid values.

2 . The detection system according to claim 1 , wherein the first processing circuitry is further configured to set a seed received from the verification server to a random number generator to calculate a random value, update the seed based on information on an area of the first storage content specified by the calculated random value, and calculate a next random value.

3 . The detection system according to claim 1 , wherein the first processing circuitry is further configured to generate an array corresponding to the first storage content, exchange information on a first area of the array specified by a random value with information on a second area of the array specified by a variable value based on a memory size of the first storage content, and generate the response based on the second area after exchange.

4 . The detection system according to claim 1 , wherein the second processing circuitry is further configured to output a warning in a case where the response received from the node does not match the verification response.

5 . The detection system according to claim 1 , wherein:

the first processing circuitry is further configured to generate an array s corresponding to memory cells of the first storage content, and wherein the random values are used to exchange a value of the array s at a randomly selected index j with a value of the array s at a current index i.

6 . The detection system according to claim 5 , wherein:

the first processing circuitry is further configured to decrement the current index i after each exchange, thereby gradually narrowing the range for the next random value.

7 . The detection system according to claim 5 , wherein:

the first processing circuitry is further configured to generate a checksum or hash digest of a memory cell corresponding to the value of the array s at the current index i after the exchange.

8 . The detection system according to claim 1 , wherein:

the first processing circuitry includes a random number generator, and the first processing circuitry is configured to acquire a random integer value from 0 to a current variable i or less from the random number generator.

9 . The detection system according to claim 1 , wherein:

the first processing circuitry is configured to generate the response information based on information on the area of the first storage content as a time-series list of checksums or hash digests generated during a random scan of the first storage content.

10 . The detection system according to claim 1 , wherein:

the node comprises communication circuitry configured to receive challenge information containing the seed from the verification server and transmit the response to the verification server.

11 . The detection system according to claim 1 , wherein:

the node comprises a storage including a flash memory or a Random Access Memory (RAM) storing the first storage content.

12 . The detection system according to claim 1 , wherein:

the second processing circuitry of the verification server is configured to set a first random number seed in a random number generator based on a nonce value included in challenge information sent to the node.

13 . A detection method of a detection system including a node and a verification server, the method comprising:

in the node,

generating a plurality of random values based on a seed received from the verification server, generating a response based on information on an area of a first storage content specified by the plurality of generated random values, and transmitting the generated response to the verification server; and

gradually narrowing a range that a next random value can take, each time a random value is generated, to preemptively exclude invalid values, and

in the verification server,

generating a plurality of random values based on the seed and generating a verification response based on information on an area of a second storage content specified by the plurality of generated random values, and

determining whether the response received from the node matches the verification response, and outputting a determination result.

14 . The detection method according to claim 13 , further comprising:

generating an array corresponding to memory cells of the first storage content;

acquiring a random integer value j; and

exchanging a value of the array at the random integer value j with a value of the array at a current index i.

15 . The detection method according to claim 14 , further comprising:

generating a checksum or hash digest of a memory cell corresponding to the value of the array at the current index i; and

updating the seed based on the checksum or hash digest.

16 . The detection method according to claim 13 , wherein:

the gradually narrowing the range comprises decrementing a variable representing a current size of a selectable range of the first storage content after each generation of a random value.

17 . A non-transitory computer-readable recording medium storing therein a detection program that causes a computer to execute a process comprising:

transmitting a seed to a node, causing the node to execute a first random scan for a first storage content based on the seed and acquiring a response resulting from the first random scan from the node;

generating a plurality of random values based on the seed and generating a verification response based on information on an area of the second storage content specified by the plurality of generated random values; and

determining whether the response received from the node and the verification response match, and outputting a determination result,

wherein the generating includes gradually narrowing a range that a next random value can take, each time a random value is generated, to preemptively exclude invalid values.

18 . The non-transitory computer-readable recording medium according to claim 17 , wherein the process further comprises:

generating an array corresponding to the first storage content; and

exchanging a value in the array specified by one of the plurality of random values with a value in the array specified by a loop variable that decreases with each iteration of the first random scan.

19 . The non-transitory computer-readable recording medium according to claim 17 , wherein the process further comprises:

generating response information in which a checksum or hash digest generated from each memory cell of the first storage content is set as a time-series list.