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Table 3 Comparison of storage and key derivation cost

From: Comprehensive evaluation of key management hierarchies for outsourced data

Hierarchy → User-based hierarchies Minimal vertex
  User User Minimal vertex resource
Attributes graph tree user hierarchy hierarchy
# of keys/users Single Multiple Single Single
# of nodes 2|U| + 1 min(|R|,2|U|) + 1 |U|+|R| |U|+|R|
# of edges O(|U||U|/2) O(min(|R|,2|U|)) O(|U||R|) O(|U||R|)
key derivation cost O(|U|) O(|U|) O(|U|) O(1)