Simon S. Lam (more
Key tree approach aka
logical key hierarchy
The key tree idea was invented by us and independently by a group in NSA (Wallner, Harder, and Agee). They wrote an Internet draft entitled, "Key Management for Multicast: Issues and Architectures," in July 1997. In the same month, we wrote a UTCS technical report, "Secure Group Communications Using Key Graphs," TR-97-23, July 28, 1997. The key tree approach is also referred to as logical key hierarchy in Internet RFCs.
The NSA draft was later revised and published as,
A revised version of our technical report was later published as,