Secure Outsourced Medical Data against Unexpected Leakage with Flexible Access Control in a Cloud Storage System

Table 1

Notations.

Notation	Description
λ	Security parameter
R	Atom role for medical staff
	Role for medical staff
	Atom role set for
P	Access policy
	Atom role set for P
	Master secret key
	Electronic medical record
PPT	Probabilistic polynomial time
	Secret credential for a role
	The encapsulated EMR
	Prefix of , defined as
	Prefix of P, defined as