[Retracted] Fog-Driven Secure Authentication and Key Exchange Scheme for Wearable Health Monitoring System

Table 1

Cryptographic techniques and limitations.

Scheme	Cryptographic techniques	Limitations
Zhang et al. [12]	(i) Utilized one-way hash function; (ii) Dynamic string generating algorithm	(i) Does not resist user traceability attacks; (ii) Does not resist desynchronization attacks; (iii) Does not resist denial-of-service attacks; (iv) Does not resist internal attacks
Li et al. [13]	(i) Utilized one-way hash function	(i) Does not resist offline identity guessing attacks; (ii) Does not resist sensor node impersonation attacks; (iii) Does not resist hub node spoofing attacks; (iv) Does not provide untraceability; (v) Does not resist desynchronization attacks; (vi) Does not provide perfect forward security; (vii) Does not provide key control
Jia et al. [19]	(i) Utilized one-way hash function; (ii) Based on bilinear pairings; (iii) Based on Diffie–Hellman problem	(i) Does not resist ephemeral secret leakage attacks; (ii) Does not resist impersonation attacks; (iii) Does not resist known session-specific temporary information attacks; (iv) Does not provide anonymity; (v) Does not provide pre-verification
Wazid et al. [20]	(i) Utilized one-way hash function; (ii) Utilized ECC	(i) Does not provide traceability; (ii) Does not resist clogging attacks