Abstract: A storage unit stores transaction data to be recorded on a blockchain. When receiving identification information identifying a processing system for processing the transaction data among processing systems, a processing unit calculates a function value using a parameter corresponding to the received identification information and a function. The processing unit notifies a determination unit, which determines the processing system for processing the transaction data from among the processing systems, of the transaction data and signature data generated from the function value.

Abstract: A verification system includes a server that includes a first processor configured to generate a hash value according to a first algorithm by using a public key associated with a user and a first message; and a terminal that includes a second processor configured to generate a collision generation value by a second algorithm based on the first message, a second message, and a private key that is paired with the public key so that the hash value is generated in a case where the collision generation value is input to the first algorithm together with the public key and the second message, and transmit the collision generation value and the second message to another terminal that is to be guaranteed that the second message has been provided by the user.

Abstract: A control method for a computer to execute a process includes accepting requests for adding a new public key to a public key group that includes a plurality of public keys aggregated in an aggregate public key used to verify validity of an aggregate signature obtained by aggregating a plurality of signatures; generating a different public key from the new public key, based on information generated from the new public key and the plurality of public keys included in the public key group; adding the new public key to the public key group; and updating the aggregate public key based on the generated different public key.

Abstract: A control method implemented by a computer, the control method including: receiving, from a user, a usage instruction that instructs to use a first service; notifying first processing that provides the first service of identification information of a second service to which the user is logged in when the usage instruction is received; receiving a condition from the first processing according to the notification of the identification information; and instructing second processing that provides the second service to notify the first processing of information according to the condition.

Abstract: A control method implemented by a computer, the control method including: receiving designation of data permitted to be accessed by a specific service, among data stored in a first storage; and in response to the receiving the designation of the data, outputting an instruction to store the designated data in a second storage isolated from the first storage.

Abstract: A generation method for a computer to execute a process includes acquiring data of a document that accepts input of signature by a plurality of users according to an attribute of the document; adding first information to the data, the first information indicating a plurality of areas in the document, the first information being used for specifying an order of requestee users of a procedure that involves the signature in a workflow regarding the document; and outputting the data of the document with the first information.

Abstract: A control method for a computer to execute a process includes detecting, by a first information processing device, a first data operation for a cloud service executed by an information processing system; notifying, by the first information processing device, a second information processing device of content of the first data operation; determining, by the second information processing device, to execute first processing on data that is a target of the first data operation based on the notified content of the first data operation; instructing, by the second information processing device, the first information processing device to execute the first processing; and executing, by the first information processing device, the first processing on the data when instructed to execute the first processing on the data.

Abstract: A signature control method implemented by a computer, the signature control method including: acquiring, by a processor circuit of the computer, a plurality of pieces of document information and signature information that corresponds to each piece of document information of the plurality of pieces of document information; generating, by the processor circuit of the computer, aggregate signature information obtained by aggregating the signature information that corresponds to the each piece of document information of the plurality of acquired pieces of document information on a basis of the plurality of acquired pieces of document information; and outputting, by the processor circuit of the computer, the generated aggregate signature information in association with aggregate public key information obtained by aggregating public key information that corresponds to the each piece of document information of the plurality of pieces of document information and the plurality of pieces of document information.

Abstract: A verification method implemented by a first system including a plurality of computers, the method includes: calculating a first hash value for an original document; calculating a second hash value for an original document by using the first hash value; calculating a first modified version's first hash value for the first modified version document; calculating a first modified version's second hash value that is a hash value obtained by combining the first modified version's first hash value and the original document's second hash value; in response to a second modified version document obtained by modifying the first modified version document, calculating a second modified version's first hash value for the second modified version document; and calculating a second modified version's second hash value that is a hash value obtained by combining the second modified version's first hash value and the first modified version's second hash value.

Abstract: A verification method implemented by a first system including a plurality of computers, the method includes: calculating a first hash value for an original document; calculating a second hash value for an original document by using the first hash value; calculating a first modified version's first hash value for the first modified version document; calculating a first modified version's second hash value that is a hash value obtained by combining the first modified version's first hash value and the original document's second hash value; in response to a second modified version document obtained by modifying the first modified version document, calculating a second modified version's first hash value for the second modified version document; and calculating a second modified version's second hash value that is a hash value obtained by combining the second modified version's first hash value and the first modified version's second hash value.