Table 1. Descriptions of various notations.

Notations	Description
U i	The patient (User)
ID i	The identity of U i
PW i	The password of U i
S	The medical server of integrated EPR information system
K	The secret key of S
c i	The counter maintained in S’s database against the user U i
H(⋅)	The secure and collision-resistance one-way hash function
p, q	Two large prime numbers
n	The publicly known modulus such that n = pq
$b{\in }_R{Z}_n^{*}$	The number b randomly chosen from $Z_n^{*}$
⊕	The bitwise XOR operator
∥	The concatenation operator
SK	The session key agreed between U i and S
𝓐	The active/passive adversary