User terminal, permission information management method, and permission information management program

A user terminal of a user of a content, comprising:

• a processor;
• and
• memory,
• wherein the memory includes computer executable instructions that when executed by the processor cause the processor to configure the user terminal to:
• generate a first key pair for an electronic signature including a user secret encryption key and a user public decryption key and a second key pair for acquiring a content decryption key including a secret decryption key and a public encryption key and to store the first key pair and the second key pair in the memory;
• transmit a permission request including the public encryption key of the second key pair to a right-holder terminal of a right holder of the content after electronically signing the permission request with the user secret encryption key of the first key pair, wherein the permission request is stored in a blockchain after the user terminal broadcasts the permission request to a network and causes a block including the permission request to be added to the blockchain, wherein the network includes at least the user terminal, the right-holder terminal, and the blockchain;
• and
• acquire, from permission information received from the right-holder terminal, a content decryption key by using the secret decryption key of the second key pair, and use the content by using the content decryption key, wherein the permission information is acquired from the blockchain by the user terminal after the right-holder terminal broadcasts the permission information to the network and causes a block including the permission information to be added to the blockchain.