# Cryptographic Protocol with Keyless Sensors Authentication for WBAN in Healthcare Applications
## 2 Related Work  
The level of security required for medical devices depends on the function of each device. It is necessary to secure the information used by medical devices so that attackers do not obtain unauthorized information or control over them, as the main information transmitted by these devices is sensitive. Many of the devices used in medicine are embedded, and most are intended to be secure at the physical level; this opens the door to targeted cyberattacks focused on sharing of secrets, private certificates, passwords, open-source bugs, cryptography, and weak authentication [8]. Different protocols, systems, or cryptographic schemes have been proposed for Implantable Medical Devices (IMDs). There are different solutions to provide security to medical scenarios with a sensor network architecture. Research on security mechanisms for WBAN can be divided into cryptographic and non-cryptographic authentication mechanisms. Cryptographic authentication mechanisms adapt lightweight traditional cryptographic schemes. Non-cryptographic authentication approaches can be divided into biometric-based, channel-based, and proximity-based authentication schemes [9]. These solutions are well-defined protocols, with security tests using protocol verification tools. The cryptographic protocols reviewed in this section were chosen due to their application, in a medical scenario, within a sensor network architecture. Most use cryptographic primitives to guarantee security services: authentication, confidentiality, and integrity. The work in [10] presents an efficient and practical authentication solution based on the scheme of [PERSON] and [PERSON] [11]. This solution uses smart card features and one-way functions. The solution presented changes the problem on which the security of [PERSON]'s scheme rests, going from discrete logarithms to hash functions. The authors performed security and efficiency analysis tests, which showed that the change in the problem does not affect the security provided by the solution. In [12], a WBAN authentication solution based on the Rabin scheme [13] and public key algorithms, is presented. The schemes used in this system are lightweight since the authors use their system on embedded devices with limited resources. The application scenario in which the solution works comprises a set of sensors and actuators connected to the WBAN and placed in the body of patients with different diseases. It has four participating entities: sensors, actuators, the node coordinator, and, a doctor. Each of these entities interacts with one another within the system. The work presented in [14] proposes an upgrade from work done by [PERSON] et al. [15] which is an authentication protocol used at Telecare Medic Information Systems (TMIS). The authors discovered that the original work was prone to diverse attacks. Through several tests with the ProVerif tool, they identified vulnerabilities related to the violation of the patient's anonymity, identity usurpation, and TMIS server attacks. Therefore, the developed protocol is resistant to those attacks and performance better, but at a computational cost. In 2015 [16], a lightweight key-handling protocol was proposed. This protocol establishes secure communication between a node with limited resources and a remote server. To ensure the protocol is secure, the authors use the AVISPA verification tool [17]. The protocol proposed by the authors considers the use of 3 entities: (1) Sensors or the restricted node (CN), (2) Remote server (UN), and (3) Third entities (\(TP_{i}\)). The three entities divide the secret among themselves. The protocol uses algorithms based on symmetric cryptography to provide confidentiality; for authentication, digital signatures are used; and hash functions are employed with Message Authentication Code (MAC) to ensure integrity.