A Secure Fair Exchange for SMS-Based Mobile Payment Protocols Based on Symmetric Encryption Algorithms with Formal Verification

Table 1

Advantages and disadvantages of the types of fairness.

Type of Fairness	Advantage	Disadvantage
No Fairness	(i) no cost of TTP	(i) very high number of messages; (ii) need for reliable network; (iii) unable to have dispute resolution
Weak Fairness	(i) low number of messages	(i) need for reliable network; (ii) full TTP
Strong Fairness	(i) semi-TTP; (ii) no need for reliable network	(i) high number of messages; (ii) cost of TTP