# Secure Proxy Re-Encryption Protocol for FANETs Resistant to Chosen-Ciphertext Attacks
###### Abstract  
In emergency situations, ensuring the secure transmission of medical information is critical. While existing schemes address on-road emergencies, off-road scenarios present unique challenges due to hazardous locations inaccessible to conventional vehicles. This research introduces a protocol for off-road emergencies, leveraging flying ad hoc networks (FANETs) formed by drones. The protocol, designed for users receiving emergency treatment, employs cryptographic techniques to protect sensitive information. To overcome the challenge of decrypting user medical records at emergency centers without the healthcare provider's key, proxy re-encryption is employed. The control center (CC) securely generates encryption and decryption keys, facilitating the re-encryption process by the cloud server (CS) and transmission to the emergency center (E). The proposed protocol, free from pairing functions, underwent security and efficiency analyses, demonstrating resilience against chosen-ciphertext attacks (CCA) and collusion resistance (CR). Execution times of approximately 0.02 and 0.0 s for re-encryption and decryption processes, respectively, for a message size of 2000 bytes highlighted the efficiency of the protocol. The research contributes a secure and efficient proxy re-encryption protocol for off-road emergency medical information transmission within FANETs.  
proxy re-encryption; FANET (flying ad hoc network); off-road accident +
Footnote †: journal: Applied  
The proposed proxy re-encryption protocol does not use pairing functions and is secure against chosen-ciphertext attacks (CCA) and is collusion-resistant (CR). The re-encryption keys are also transmitted in encrypted form, ensuring the confidentiality of the original encryption keys. Security analysis is conducted in Section 5, where we formally prove unidirectional proxy re-encryption CCA security, prove unidirectional proxy re-encryption collusion-resistant (CR) security, and explain the defense mechanism against proxy forgery attacks. In Section 6, an efficiency analysis is conducted. The complexity of the proposed scheme is analyzed, and based on that, a comparative analysis is performed with relevant studies. When compared with the best efficient paper [2], it was found to exhibit the same complexity. The implementation of the re-encryption and decryption processes, for time measurements for a message size of 2000 bytes, resulted in execution times of approximately 0.02 and 0.0 s, respectively. Consequently, the paper proposes that the proxy re-encryption protocol demonstrates a secure and efficient performance, free from the use of pairing functions, and resilient against CCA and collusion attacks.  
Our paper is structured as follows: Section 1 is an introduction, providing an overview of the research's significance, methodology, and overall results. In Section 2, we delve into related studies and establish the application scenarios to be employed in this paper. Section 3 constitutes the security building blocks of this paper, introducing seven algorithms. Utilizing these algorithms, Section 4 constructs a protocol for the application scenarios. Section 5 conducts a security analysis, while Section 6 performs an efficiency analysis. Finally, Section 7 concludes the paper.