# Secure Encapsulation Schemes Using Key Recovery System in IoMT Environments
###### Abstract  
Recently, as Internet of Things systems have been introduced to facilitate diagnosis and treatment in healthcare and medical environments, there are many issues concerning threats to these systems' security. For instance, if a key used for encryption is lost or corrupted, then ciphertexts produced with this key cannot be decrypted any more. Hence, this paper presents two schemes for key recovery systems that can recover the lost or the corrupted keys of an Internet of Medical Things. In our proposal, when the key used for the ciphertext is needed, this key is obtained from a Key Recovery Field present in the cyphertext. Thus, the recovered key will allow decrypting the ciphertext. However, there are threats to this proposal, including the case of the Key Recovery Field being forged or altered by a malicious user and the possibility of collusion among participating entities (Medical Institution, Key Recovery Auditor, and Key Recovery Center) which can interpret the Key Recovery Field and abuse their authority to gain access to the data. To prevent these threats, two schemes are proposed. The first one enhances the security of a multi-agent key recovery system by providing the Key Recovery Field with efficient integrity and non-repudiation functions, and the second one provides a proxy re-encryption function resistant to collusion attacks against the key recovery system. CL-PKC; key encapsulation; key recovery system; proxy re-encryption; signcryption 2021213474. 213474.  
system. When a user needs a key that was used to create a ciphertext, a newly defined field known as Key Recovery Field (KRF) can be used to recover the key. If key is lost or corrupted, the recovered key can be used to decrypt the ciphertext. Because security is necessary for key management and recovery in various environments using IoT, there is much research on key recovery systems for use with IoT. [PERSON] et al. [6] proposed a secure group key distribution scheme for untrusted wireless networks. [PERSON] et al. used the Self-healing Group Key Distribution (SGKD) protocol to ensure group communication security and improve communication efficiency. Instead of requiring the group manager to resend the missing key to update the message, [PERSON] et al. proposed a scheme for group members to recover the lost session key from the current broadcast message. [PERSON] et al. [7] proposed an efficient and secure key distribution and key recovery mechanism suitable for the characteristics of the IoT environment. The proposed system added the key recovery function required to prevent the reverse function of the encryption and key recovery, providing security to both due to the communication device could not unilaterally recover the key. In addition, it is efficient because there is little information sent during key recovery, which is suitable for IoT environments. [PERSON] [8] proposed a scheme to support secure sensor data for cloud computing to activate services at the IoT application level. [PERSON] proposed key management that enables continuous key authentication for the privacy of sensing information in such a cloud computing environment and enables secure recovery if the key is lost or corrupted. Losing a key in an IoMT environment will prevent access to information such as previous medical treatment data and information on medications being taken, and impede accurate medical examination and treatment. Therefore, key management is important in IoMT environments [9]. There are four agents in a key recovery system in IoMT. The key Generation Center (KGC) can generate some parameters of a network participant's public key pair. The Medical Institutions (Med) have all the medical treatment data, The key Recovery Center (KRC) can recover the complete key. The key Recovery Agent or Key Recovery Auditor (KRA) can share the KRC's key recovery operations or monitor other agencies. If the patient loses the key used for the ciphertext, the key can be recovered with the help of remains the KRF, Med, KRC, and KRA.