Table 2. Key terms and descriptions.

Symbol	Description	Symbol	Description
RID	Requester ID	TK	Encrypted text
θ	Validity period	ϑ	Other vital information associated with patient or third-party user
RBK i	User i public key	Ð	Data
Gateway id	Admin ID	M	Original message
RType	Third-party user’s request type	U y	Users (general)
List i	A given list	U y1U	Third-party user
IndexList i	A given Index list	U y2G	Gateway (admin) user
request i	A given request	U y3P	Patient user
G′ and G′′	Multiplicative cyclic groups of prime order p	A	Adversary
h	The generator of G′	hf(.)	Hash function
m	A bilinear map function	K pub	Public key
x,y ∈	Elements of G′	M K	Master key
s,t,w	Elements of ℤp	K prv	Private key
Aatr = {a1……,aN}	A set of attributes	δ, δ’, h2, φ1, φ2, σ, η, ρ	Random values
U and AS	Attribute list of users and access structures, respectively	DBDH	Decisional Parallel Bilinear Diffie-Hellman Exponent