Data management system with tamper-evidence

A data management method, comprising:

• issuing, by a first computer system of one or a plurality of first computer systems, a state update request in which a target is specified to a second computer system that communicates with the one or a plurality of first computer systems;
• receiving, by a node systems of one or more node systems in the second computer system, the state update request and executing, by the node system, processing of updating a state of the target specified in the state update request;
• adding, by the node system, an object to an asset for the target in an asset set managed by the node system in the executing,
• the object being data that represents the state of the target,
• the asset being assigned to each target,
• the asset being a time series of objects,
• the asset set being a set of assets,
• the asset set having a DAG (Directed Acyclic Graph) structure,
• in the asset set having the DAG structure, a node being the object, and an edge representing a relationship between objects in one or more steps of processing of updating states of one or more objects, and
• the added object being a terminal object in the asset for the target specified in the state update request;
• and
• outputting, by the node system, a proof of existence that is the terminal object or a summary thereof,
• the output proof of existence being saved in an external system managed by a management entity different from a management entity for the node system.

A data management method, comprising:

• receiving, by a node system of one or a plurality of node systems in a second computer that communicates with one or a plurality of first computer systems, a state update request in which a target is specified;
• executing, by the node system, processing of updating a state of the target specified in the state update request;
• adding, by the node system, an object to an asset for the target in an asset set managed by the node system in the executing,
• the object being data that represents the state of the target,
• the asset being assigned to each target,
• the asset being a time series of objects,
• the asset set being a set of assets,
• the asset set having a DAG (Directed Acyclic Graph) structure,
• in the asset set having the DAG structure, a node being the object, and an edge representing a relationship between objects in one or more steps of processing of updating states of one or more objects, and
• the added object being a terminal object in the asset for the target specified in the state update request;
• and
• outputting, by the node system, a proof of existence that is the terminal object or a summary thereof,
• the output proof of existence being saved in an external system managed by a management entity different from a management entity for the node system.

A data management method, comprising:

• issuing, by a first computer system of one or a plurality of first computer systems that communicate with a second computer system including one or a plurality of node systems, a state update request in which a target is specified to the second computer;
• a node systems of the one or a plurality of node systems being configured to receive the state update request and executing, by the node system, processing of updating a state of the target specified in the state update request;
• the node system being configured to add an object to an asset for the target in an asset set managed by the node system in the executing,
• the object being data that represents the state of the target,
• the asset being assigned to each target,
• the asset being a time series of objects,
• the asset set being a set of assets,
• the asset set having a DAG (Directed Acyclic Graph) structure,
• in the asset set having the DAG structure, a node being the object, and an edge representing a relationship between objects in one or more steps of processing of updating states of one or more objects, and
• the added object being a terminal object in the asset for the target specified in the state update request;
• and
• the node system being configured to output a proof of existence that is the terminal object or a summary thereof,
• the output proof of existence being saved in an external system managed by a management entity different from a management entity for the node system including the second management unit,
• the external system being the first computer system or a storage system that is accessible from all of the one or a plurality of first computer systems including the first computer system, and
• receiving, by the first computer system, the proof of existence from the second computer system and saving, by the first computer system, the proof of existence, and then receiving, by the first computer system, the terminal object or the summary thereof from the second computer system, and using, by the first computer system, the terminal object or the summary thereof and the saved proof of existence to determine whether the terminal object is tampered with.

A non-transitory computer readable medium, storing instructions that are executed by one or more processors for causing a node system of one or a plurality of node systems in a second computer system that communicates with one or more first computer systems to:

• receive a state update request in which a target is specified;
• execute processing of updating a state of the target specified in the state update request;
• add an object to an asset for the target in an asset set managed by the node system in the executing,
• the object being data that represents the state of the target,
• the asset being assigned to each target,
• the asset being a time series of objects,
• the asset set being a set of assets,
• the asset set having a DAG (Directed Acyclic Graph) structure,
• in the asset set having the DAG structure, a node being the object, and an edge representing a relationship between objects in one or more steps of processing of updating states of one or more objects, and
• the added object being a terminal object in the asset for the target specified in the state update request;
• and
• output a proof of existence that is the terminal object or a summary thereof,
• the output proof of existence being saved in an external system managed by a management entity different from a management entity for the node system.

A non-transitory computer readable medium, storing instructions that are executed by one or more processors for causing a first computer system of one or a plurality of first computer systems that communicate with a second computer system including one or a plurality of node systems to:

• issue a state update request, in which a target is specified, to the second computer system;
• a node system of the one or more node systems being configured to receive the state update request and execute, by the node system, processing of updating a state of the target specified in the state update request;
• the node system being configured to add an object to an asset for the target in an asset set managed by the node system
• the object being data that represents the state of the target,
• the asset being assigned to each target,
• the asset being a time series of objects,
• the asset set being a set of assets,
• the asset set having a DAG (Directed Acyclic Graph) structure,
• in the asset set having the DAG structure, a node being the object, and an edge representing a relationship between objects in one or more steps of processing of updating states of one or more objects, and
• the added object being a terminal object in the asset for the target specified in the state update request;
• the node system being configured to output a proof of existence that is the terminal object or a summary thereof,
• the output proof of existence being saved in an external system managed by a management entity different from a management entity for the node system including the second management unit, and
• the external system being the first computer system or a storage system that is accessible from all of the one or a plurality of first computer systems including the first computer system;
• and
• receive the proof of existence from the second computer system and save the proof of existence, and then receive the terminal object or the summary thereof from the second computer system, and use the terminal object or the summary thereof and the saved proof of existence to determine whether the terminal object is tampered with.