초록 ▼

This invention provides a method for identifying a purchaser who purchased content from which an illegal copy was produced. A provider system encrypts purchased by the purchaser using a public key of a purchaser system and sends the encrypted content to the purchaser system. The purchaser system cre

This invention provides a method for identifying a purchaser who purchased content from which an illegal copy was produced. A provider system encrypts purchased by the purchaser using a public key of a purchaser system and sends the encrypted content to the purchaser system. The purchaser system creates a digital signature of the content with the use of a private key of its own and embeds the created digital signature into the received content. When an illegal copy is found, the provider system verifies the digital signature, embedded in the illegal copy as a digital watermark, to identify the purchaser who purchased the content from which the illegal copy was produced.

대표청구항 ▼

1. A validity check system comprising:an information browser device which displays digital data; and an information publisher device which stores said digital data in a state that said digital data can be displayed in said information browser device, wherein said information publisher device compris

1. A validity check system comprising:an information browser device which displays digital data; and an information publisher device which stores said digital data in a state that said digital data can be displayed in said information browser device, wherein said information publisher device comprises: a storage unit which stores check data which has been related to a digital data validity check unit in a state that said check data may be displayed in said information browser device together with said digital data, wherein said information browser device comprises: a display unit which displays said digital data and said check data, and wherein said digital data validity check unit displays validity checkable information on said display device with which it is possible to check validity of said digital data displayed on said display device together with said check data.