See Tier 0.
CNSSI 4009-2015 under central facility (or Tier 0)
The composite facility approved, managed, and operated under National Security Agency (NSA) oversight that includes:
a. National COMSEC Material Generation and Production facilities for physical and electronic keys, both traditional and modern.
b. Central Office of Record (COR) services for NSA, contractor, and select Civil Agency accounts.
c. National Distribution Authority (NDA) for U.S. accounts worldwide.
d. National Registration Authority for all non-military accounts on U.S. systems.
e. National Credential Manager for all electronic key management system (EKMS) accounts on U.S. systems.
f. EKMS Defense Courier Service (DCS) data administrator.
CNSSI 4009-2015 under Tier 0 (central facility) (COMSEC)