The Johns Hopkins University Applied Physics Laboratory This document defines a protocol for negotiating scoped security associations between Bundle Protocol version 7 (BPv7) agents within a delay-tolerant network (DTN). Security associations are used to amortize the costs of asymmetric-keyed security operations and allow for efficient and high-throughput BPv7 security within a public key infrastructure. This protocol also provides for unilateral re-keying of established security associations in a delay-tolerant manner.