Abstract: This paper presents a new protocol based on the hierarchical model.The protocol adopts the detection mechanism to obtain the values on the region of the text cover object，and the embeddable region is determined by the above values and threshold.The protocol can improve the stealthiness of the text watermarking algorithm.The experiment indicates that the anti-aggressivity of the algorithm working in conjunction with the protocol increases obviously than using it alone.

Key words: text watermarking, hierarchical model, stealthiness

摘要： 提出了一种基于层次模型的规则。规则中采用检测机制在文本宿主文件区域上得到检测值，并依据该检测值和极限值来确定嵌入水印信息的区域。依据该规则，提高了已有文本数字水印算法的隐蔽性。实验分析表明与该规则结合使用的算法抗攻击性与单独使用算法相比较有明显提高。

关键词: 文本水印, 层次模型, 隐蔽性