It covers the on-line distribution of cryptographic keys among the Key Management Centres authoritative in their respective domains. It also deals with the exchange between a Key Management Centre and its own domain KMAC entities.
The library provides a simple C language application programming interface (API) to access and parse UNISIG SUBSET-137 messages and is licensed under both open source and commercial versions.
General architecture of KMS
Picture from UNISIG “Subset-137 On-line Key Management FFFIS v1.0.0”