# Tamper and Clone-Resistant Authentication Scheme for Medical Image Systems
## 1 Introduction  
In the universal declaration of human rights, health and medical care are considered as fundamental rights of humans [1]. Any try to tamper, exploit, or misuse the healthcare information systems are not only an illegal operation but also threatens human rights. For instance, tampering with medical images can lead to wrong diagnosis and treatment [2]. Therefore, the need for a secure healthcare information system increases steadily every day. Telehealth and/or telemedicine applications provide a good tool for remote clinical services such as exchanging digital medical images, patient's information, etc. the so-called medical information. These services and others face several challenges, for instance, \"developing tools to enable risk assessment, developing a method for unique patient identification, identifying practices to safely manage medical information transmissions\" [3]. Particularly, the medical image transmission overinsecure networks has many security challenges; firstly, a small alteration in the region of interest in medical images (region used for the medical diagnosis) can affect the patient's life. Therefore, mandatory security requirements must be followed by users of medical images such as confidentiality, integrity, availability, authenticity, and data traceability [4]. Recently, a new hardware-oriented approach has been presented. It is based on hardware security modules that play an important role in ensuring the trustworthiness and integrity of electronic systems. Such modules provide each electronic device in a system with random digital signatures [5]. In [6], the Physical Unclonable Function (PUF) was proposed to be the backbone of a medical image system. PUFs can here be perceived as device-intrinsic electronic fingerprints. Due to the PUF, the proposed unclonable medical image system in [6] could securely exchange medical images. Unfortunately, the unclonable medical image system such as other similar systems deploying PUFs suffers from the well-known PUF-drawbacks and vulnerabilities such as the noisy and inconsistent responses together with a limited number of PUF- challenge-response pairs [7]. On the other hand, a Secret Unknown Cipher (SUC) was introduced as an alternative to the PUFs in [8]. Physically clone-resistant identities based on SUC were first proposed to provide an electronic device with the so-called electronic DNA (e-DNA) in [8] and [9]. The target of SUCs is to prevent tamper and cloning attacks by embedding a low-complexity, non-repeatable, and unpredictable cryptographic function in an electronic device. Such a function is considered highly consistent and error-free comparing to PUFs. This work presents a possible approach towards constructing a clone-resistant watermarking system by providing each electronic device in the medical image system with a clone-resistant unpredictable unique digital SUC signature. The main contribution of this paper is to propose a clone-resistant watermarking system for medical images based on difference expansion watermarking and SUC techniques. The unpredictable, unclonable, unique watermark signature is generated by using SUC. Pertinent features extracted from the DICOM image are used as input to the Jacobian model [10] in order to build a meaningful watermark. This watermark is signed with the SUC-output in order to obtain a clone resistant signed watermark. The combination of SUC with watermarking ensures strong integrity, and authenticity and provides a high level of security to the medical image system. Indeed, in addition to the reversibility of the proposed watermarking, which ensures the retrieval of the original medical image at the extraction phase as well as good resistance against image processing attacks, SUC as a clone resistant identity can prohibit any image faking and tampering attacks efficiently. The paper is organized as follows:  
* The state of the art of watermarking, PUFs, and some related works are summarized in Section 2.