# Mutual Authentication Protocol for D2D Communications in a Cloud-Based E-Health System
## 3 Related Work  
[PERSON] et al. [6] and [PERSON] et al. [7] considered a cloud server an auxiliary entity that stores patients' data, such as measures collected from sensors coupled to their bodies. Such data are encrypted and transmitted over public channels from the entities involved with the cloud server and vice versa, after the execution of mutual authentication and the generation of a session key. The authors designed protocols based on asymmetric and symmetric cryptography composed of four phases, namely health center upload (HUP), patient upload (PUP), treatment (TP) and checkup (CP). A security analysis that was conducted revealed some issues in the protocol of [PERSON] et al. [7]. According to [PERSON] et al. [6], it fails to preserve system anonymity and security if the patient's device is lost or stolen. On the other hand, the protocol of [PERSON] et al. [5] fails to avoid a denial of service (DoS) attack. [PERSON] et al. [8] and [PERSON] et al. [9] also developed interesting approaches. Although the protocols considered no auxiliary cloud server (the entities authenticate themselves directly with the health center server through the Internet), they were developed for e-health/m-health/TMIS, similar to our protocol. The proposal of [PERSON] et al. [9] is based on asymmetric cryptography, whereas that designed by [PERSON] et al. [8] is based on symmetric cryptography. Both are composed of three phases in common, namely Initialization, Registration, and Authentication. [PERSON] et al. [9] accomplished all the security objectives considered in the security analysis section of this manuscript, while [PERSON] et al. [8] is vulnerable to the stealing of a patient's device and involve confidentiality issues. The protocols of [PERSON] et al. [10], [PERSON] et al. [11] and [PERSON] et al. [12] differ from those of [PERSON] et al. [7] and [PERSON] et al. [6] because they consider only the communication channel between the user (patient) and the cloud for security purposes. They also employ asymmetric cryptography based on the elliptic curves discrete logarithm problem (ECDLP) and comprise three phases, namely initialization, registration, and login/authentication. [PERSON] et al. [10] and [PERSON] et al. [11] accomplished all the security objectives analyzed in this study; however, the protocol of [PERSON] et al. [12] shows some security issues, such as lack of confidentiality and vulnerability to patient trackability due to loss/stealing of the patient's mobile device. Finally, the protocols of [6; 7; 8; 9; 10; 11; 12] would better attend m-health requirements if D2D communication was used, because they would require less processing time, use of the device's energy and band usage, reflecting in the reduction of costs. [PERSON] et al. [13] proposed a hybrid model for Long Term Evolution (LTE) network-assisted D2D discovery and communication towards the integration of D2D into the 3 GPP LTE architecture through the development of a device's direct discovery model and optimization of the establishment of communications. It is based on the Proximity Services (ProSe) standard developed by 3 GPP and its security requirements for D2D communication. However, it does not consider m-health adapted architecture and, consequently, would need to receive modifications to guarantee the security necessary for m-health. [PERSON] et al. [14] developed an m-health authentication scheme for D2D communication. Based on the ECDLP, it is a certifiateless signcryption scheme (CLGSC) that considers the necessity of protecting data from eavesdropping on the relays involved in D2D communication. However, it differs from ours because it does not consider a cloud server an auxiliary in the scheme. Our protocol uses D2D communication for e-health/m-health/TMIS for enabling the transmission of large amounts of data, such as health reports with images, sound, and video, between devices in a short-range.