Protecting against Key Exposure: Strongly Key-Insulated Encryption with Optimal Threshold
Mihir Bellare, Adriana Palacio · 2002
A new framework for protection against key exposure was recently suggested by Dodis et. al. [16]. We take its realization further towards practice by presenting simple new schemes that provide benefits over previous ones in terms of scalability, performance and security. Our first contribution is a simple, practical, scalable scheme called SKIE-OT that achieves the best possible security in their framework. SKIE-OT is based on the Boneh-Franklin identity-based encryption (IBE) scheme [10] and exploits algebraic properties of the latter. We also present a general transform which can be applied to yield alternative practical schemes with the same security characteristics as SKIE-OT, starting from other IBE schemes such as that of Cocks [14]. Finally, we show that the role of identity-based encryption is not coincidental by proving that IBE is equivalent to (not strongly) key-insulated encryption with optimal threshold and allowing random-access key updates.