A secure and reliable bootstrap architecture

TLDR

In computer systems, higher layers assume lower layers are trustworthy, and an integrity chain guarantees system security only when each layer’s integrity is verified—a condition often unmet during bootstrapping, yet critical for commerce, security, and active networks. This paper introduces the AEGIS architecture to initialize a computer system. AEGIS validates integrity at every layer transition during boot and includes a recovery process for failures. The recovery mechanism enables robust systems by maintaining integrity even when checks fail.

Abstract

In a computer system, the integrity of lower layers is typically treated as axiomatic by higher layers. Under the presumption that the hardware comprising the machine (the lowest layer) is valid, the integrity of a layer can be guaranteed if and only if: (1) the integrity of the lower layers is checked and (2) transitions to higher layers occur only after integrity checks on them are complete. The resulting integrity "chain" inductively guarantees system integrity. When these conditions are not met, as they typically are not in the bootstrapping (initialization) of a computer system, no integrity guarantees can be made, yet these guarantees are increasingly important to diverse applications such as Internet commerce, security systems and "active networks". In this paper, we describe the AEGIS architecture for initializing a computer system. It validates integrity at each layer transition in the bootstrap process. AEGIS also includes a recovery process for integrity check failures, and we show how this results in robust systems.