Immutable Authentication and Integrity Schemes for Outsourced Databases

Database outsourcing enables organizations to offload their data management overhead to the external service providers. Immutable signatures are ideal tools to provide authentication and integrity for such applications with an important property called immutability. Signature immutability ensures that, no attacker can derive a valid signature for unposed queries from previous queries and their corresponding signatures. This prevents an attacker from creating his own de-facto services via such derived signatures. Unfortunately, existing immutable signatures are very computation/communication costly, which make them impractical for real-life applications. In this paper, we developed three new schemes called practical and immutable signature bouquets (PISB), which achieve efficient immutability for outsourced databases. PISB schemes are simple, non-interactive, and computation/communication efficient. Our generic scheme can be constructed from any aggregate signature coupled with a standard signature. Our specific scheme is constructed from Condensed-RSA and Sequential Aggregate RSA. It has a low verifier computational overhead and compact signature. Our third scheme offers the lowest end-to-end delay among existing alternatives by enabling efficient signature pre-computability. We provide formal security analysis of PISB schemes (in Random Oracle Model) and give a theoretical analysis on the relationship between signature immutability and signature extraction. We also showed that PISB schemes are more efficient than previous alternatives.