초록 ▼

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

This invention provides a method for identifying a purchaser who purchased content from which an illegal copy was produced. A provider system encrypts a content 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 ▼

[ What is claimed is:] [1.] An embed-in-content information processing method for embedding information on k (k is an integer equal to or larger than 2) content-handling persons using an electronic computer, the method comprising the steps of:creating a digital signature of a first content-handling

[ What is claimed is:] [1.] An embed-in-content information processing method for embedding information on k (k is an integer equal to or larger than 2) content-handling persons using an electronic computer, the method comprising the steps of:creating a digital signature of a first content-handling person by encrypting a hash value using a private key in accordance with a public key cipher system of the first content-handling person, the hash value being created by evaluating the content with a first hash function;sequentially repeating digital signature creation for a second person to a k-th content-handling person to create the digital signatures of the content-handling persons; andembedding the digital signature of the k-th content-handling person into the content such that the digital signature of the k-th content-handling person cannot be separated from the content without using a predetermined rule, the digital signature of the k-th content-handling person being obtained by performing said digital signature creation for the k-th content-handling person, wherein, during said digital signature creation processing for an i-th content-handling person (i is an integer between 2 and k), a value dependent on the digital signature of the (i-1)th content-handling person is encrypted using the private key of the i-th content-handling person to generate the digital signature of the (i-)th content-handling person.