公开(公告)号：GB2344666A

公开(公告)日：2000-06-14

申请号：GB9921762

申请日：1999-09-16

Applicant: IBM

Inventor： HIRAYAMA YUKI ,  AMANO TOMIO ,  SHIMIZU SCHUICHI ,  MORIMOTO NORISHIGE

IPC: G06F12/14 ,  G06F17/21 ,  G06F21/24 ,  G06T1/00 ,  G06T11/60 ,  G06F1/00

Abstract: Embedding information, particularly electronic watermark information, in document data that includes text and is written in a page/content description language. A sequence of locations where the information is to be embedded is generated, based on an analysis of the layout of the document data and using a string of sequential pseudo-random numbers (Figs. 1 and 7). The embedded information can comprise a change in pitch between two designated characters and their succeeding characters (Fig. 3). Alternative, more "robust" watermarks are also described. In one (Fig. 9), a page description that represents either a relative distance travelled from a reference point of a string of characters in which the information is to be embedded, or a relative distance travelled from a reference point of the previous character, is changed: an "equalization attack" destroys the watermark information but also damages the document appearance (Fig. 4). In another, a "compound font" can be used in the page description to replace one or more characters (Figs 5 and 10). Alternatively, the page description data is changed so that a graphic primitive is used to replace a selected character (Figs. 6 and 11).