Privacy-Preserving Two-Factor Key Agreement Protocol Based on Chebyshev Polynomials

Table 2

The notations.

Symbol	Description
S	The server
U	A user
PW	U’s password
ID	U’s identity
s	The master key of the server
x	A variable with value in [−1,1]
⊕	Exclusive-OR operation
h()	A one-way hash function
||	String concatenation
T1, T2, T3	The timestamps
t	A random integer
SK	Session key
Ek()	Symmetric encryption algorithm with k
Dk()	Symmetric decryption algorithm with k