Patent ID: 7266700
Filing Date: 2007-09-04
Classification: G11B,H04K,H04L

Abstract:
1. A code-string generating method comprising: a generation step of generating a first code string and a second code string from at least part of an original code string obtained by coding a signal, the first code string containing a code string having a low playback quality and the second code string being used for increasing the quality of a playback signal of the first code string; and an encryption step of encrypting the second code string, wherein, in said encryption step, a first portion of the second code string having an exact or almost regular pattern is encrypted by a first encryption process, or the first portion is not encrypted, and a second portion, which is part of the second code string other than the first portion, is encrypted by a second encryption process different from the first encryption process, and wherein part of or all of the first portion is embedded at a position in the first code string which is ignored when the first code string is played back.