Telecare medical information systems (TMIS) allow patients remotely login medical service providers to acquire their medical information and track their health status through unsecured public networks. Hence, the privacy of patients is vulnerable to various types of security threats and attacks, such as the leakage of medical records or login footprints and the forgery attacks. Many anonymous three-factor authentication and key agreement (AKA) schemes have been proposed for TMIS with single server, but none of them is suited for TMIS with multiple servers. In this paper, we propose a biometric-based three-factor AKA scheme to protect user anonymity and untraceability in TMIS with multiple servers. We will construct a security model of a three-factor AKA scheme with user anonymity in TMIS with multiple servers, and give a formal security proof of the proposed scheme. The security of the proposed scheme is based on the elliptic curve decisional Diffie-Hellman problem assumption and hash function assumption. We will show that the proposed scheme is efficient enough for low-power mobile devices.

A Physical Unclonable Function (PUF) provides a physical device a unique output for a given input, which can be regarded as the device’s digital fingerprint. Thus, PUFs can provide unique identities for billions of connected devices in Internet of Things (IoT) architectures. Plenty of PUF based authenticated key exchange (AKE) protocols have been proposed. However, most of them are designed for the authentication between an IoT node and the specific server/verifier, whom the IoT node registered with. Only a few of them are designed for the authentication between IoT nodes, and all these protocols need verifiers or explicit Challenge-Response Pairs (CRPs). In this paper, we propose the first PUF based AKE protocol for IoT without verifiers and explicit CRPs, which IoT nodes can freely authenticate each other and create a session key on their own without the help of any server or verifier. We compare the proposed protocol with 27 relevant PUF based AKE protocols to show the superiority, and analyze the computational cost of each entity in the proposed protocol to show the efficiency. We define the adversarial model of a PUF based AKE protocol for IoT and formally prove the security of the proposed protocol in random oracle model. The security of the proposed protocol is based on the Elliptic Curve Discrete Logarithm (ECDL), Elliptic Curve Computational Diffie-Hellman (ECCDH), and Decisional Bilinear Diffie-Hellman (DBDH) assumptions.

Steganography is the practice of hiding information or data in a seemingly innocuous cover medium, such as message, file, image, audio, and video. In the past decades, many approaches of steganography in images were proposed for various applications. In social communication and the information highly exposed society, steganography requires high embedding capacity to transmit secret data efficiently. Generally, there is a trade-off between fidelity and embedding capacity. In this paper, we propose a novel and efficient data hiding algorithm in 24-bit color images with super high embedding capacity and acceptable peak signal-to-noise ratio (PSNR) using spatial-domain-adjacent mean. In the proposed algorithm, the embedding rate is about 7.4 bits per pixel (bpp) when the PSNR is nearly 30, and the embedding rate is about 8.88 bpp when the PSNR is nearly 25. The advantage of the proposed method is no need to transform data in another domain and without training data. Experiments also demonstrate the imperceptibility under some state-of-art steganalysis. The proposed steganography provides an efficient way to transmit sensitive information in the information highly exposed society.

Certificate-based public key cryptography (CB-PKC) removes the problem of certificate management in traditional public key systems and avoids the key escrow problem in identity-based public key systems. In the past, many authenticated key exchange (AKE) protocols based on CB-PKC systems, called CB-AKE, were proposed to be applied to secure communications between two remote participants. However, these existing CB-AKE protocols become insecure since attackers could compute and obtain the whole secret key from some partial leaked information of the secret key by side channel attacks. In this paper, our goal is to propose the $first$ CB-AKE protocol with the property to resist side channel attacks, called leakage-resilient CB-AKE (LR-CB-AKE). The proposed LR-CB-AKE protocol is formally proven to be secure in the generic bilinear group (GBG) model under the discrete logarithm (DL) and computational Diffie-Hellman (CDH) assumptions.