Abstract: In light of the drawbacks of current digital watermarking protocols, such as requiring frequent involvement of buyers, assuming that buyers' knowledge of signature or watermark, and not considering appropriate usage control of digital products, a secure, practical and extensible watermarking protocol was proposed, by utilizing the homomorphic, commutative El Gamal encryption algorithm and the machine fingerprint-based copyright control scheme. Besides the basic functions of the digital watermarking protocol, this protocol also considered the interests of both buyer and seller to some extent, and improved user's experience with a transaction model similar to the traditional one.

Key words: Digital Rights Management (DRM), watermarking protocol, El Gamal encryption algorithm, usage control, machine fingerprint

摘要： 针对目前数字水印协议中需要买方的频繁参与、要求买方了解签名或水印生成嵌入等技术以及没有很好地考虑到数字产品的使用控制等问题，提出一种安全实用、可扩展的数字水印协议。该协议利用具有同态性和可交换性的El Gamal加密算法及基于机器指纹的版权控制方案，在实现数字水印基本功能的同时，相当程度上兼顾了买卖双方的权益，以更接近传统交易的模式，改进用户的体验。

关键词: 数字版权管理, 数字水印协议, El Gamal加密算法, 使用控制, 机器指纹