Learn in the textbookSecurity Testing and IoT / Hardware Protection
DefinitionA digital watermark (電子透かし) is a technique for embedding information such as the copyright holder or an identification number into digital content like images, audio and video, with almost no change to how it looks or sounds.
ExplanationThe embedded information survives in copied data, so when unauthorized use turns up it gives a lead on the rights holder or the source of the leak. Unlike encryption, the data itself stays open for anyone to view or listen to.
AnalogyLike a name tag sewn inside a garment: out of sight normally, but it tells you the owner when you check.
Memory hookThe English word watermark (water + mark) comes from a mark pressed into paper while it is still wet; a digital watermark moves that mark into the data.