Toward hierarchical identity-based cryptography for tactical networks

The nature of the tactical network environment requires using secure, reliable, highly efficient, low delay communication protocols. This is particularly true of cryptographic key management protocols that must be successfully completed prior to the start of sensor and C4ISR communications. One class of cryptographic techniques, noninteractive (i.e., identity-based) cryptosystems, is particularly attractive in this environment since these systems can share a key between tactical network nodes who know the identity of their peer and without exchanging cryptographic information. However, while a number of such systems exist no non-interactive hierarchical system providing complete resistance to user compromise, exists. In this paper we present such a new key-sharing scheme that minimizes the computational burden on network nodes in the most common key establishment situations. The scheme supports a hierarchy of authorities which provide keys to users and may reconfigure themselves (e.g., changing their parent in the hierarchy when needed to reflect force movements or other system reconfigurations), and cryptographically strong protection against user compromise. We also present an alternative form of our hierarchical system that has better computational costs in the common case, and provides unconditionally strong protection against a configurable threshold number of user compromises.