Method for embedding codes, method and apparatus for restoring identification information

摘要

According to the embodiments of the present invention, identification information that is embedded by the fingerprinting scheme cannot be read out by the third party, which can protect privacy of a user. Specifically, when converting an identification number u of a user to remainder codes q₁, q₂, . . . , q_N, and embedding thus obtained remainder codes into content information by digital watermark embedding processing, the identification number u or remainder codes u₁, . . . , u_N are encrypted based on a secret key s. Accordingly, even though the third party who does not know the secret key s improperly detects a digital watermark to obtain an encrypted identification number v, the valid identification number u before encryption cannot be obtained. Thus, privacy of the user can be protected.