Proxy Re-Cryptography

Proxy re-cryptography can be used to solve the trust problem in the scenarios men-

tioned in Chapter 1. Besides, there are many promising applications.

Many companies have developed digital rights management (DRM) technologies,

which can prevent illegal redistribution of digital content. With DRM systems, the dig-

ital content can only be played in a specified device (regime). For example, a song

playable in device (regime) A cannot be played in device (regime) B. However, it is

reported that 86% of the consumers prefer to pay twice the price for a song that can

run on any device than that with one single device [155]. Most of current interoperabil-

ity architectures require to change the existing DRM systems significantly [176]; this

modification cannot be adopted due to business reasons. At ACM DRM 2006, Taban

et al. [271] proposed a new interoperability architecture, which does not change the

existing DRM systems too much but maintains the DRM systems’ security. In their

architecture, only a new module called domain interoperability manager (DIM) is in-

troduced. DIM applies a single signature scheme and a single public key encryption

scheme that can transform licences and content in regime A into ones in regime B,

but it cannot generate valid licenses or content either in regime A or in regime B. It

is easy to see that the traditional signature and public key encryption cannot support

transformation, which, however, can be easily implemented by proxy re-cryptography.