Content Extraction Signatures Revisited

Public verifiability makes standard digital signature a widely used cryptographic mechanism in various Internet applications. Unfortunately, it seriously damages the privacy of some participants under some application scenarios. In the literature, most researchers improve the privacy protection of digital signature via restricted verifiability. In fact, some works alternatively focus on the possibility of removing sensitive information from a digital signature before it became available to the public. The content extraction signature is a typical example of this interesting strategy. In this paper, weaknesses of a previous content extraction signature scheme are pointed out first, then an improved scheme will be presented. The improved scheme is in fact a generic construction and provides adequate privacy protection in comparison with previous works. Besides, the new construction shows that the two main strategies can be employed simultaneously and cooperatively.