Digital image have become the main source of human information acquisition and exchange, which is widely used in aerospace, biomedical and military fields. Therefore, to ensure the secure transmission of digital image, this paper proposes a secure spatio-temporal chaotic pseudorandom generator for image encryption is proposed. Firstly, we consider the potential impact of precision loss in digital circuits on the degradation of chaotic systems. Therefore, we employ the unscented Kalman filter (UKF) to assess accuracy loss in both Logistic, Sine and Chebyshev maps, which is compensated for by introducing perturbations into the spatio-temporal chaotic system. Secondly, we design new Sine maps and Chebyshev maps with time-varying delays to perturb the time dimension of the non-adjacent coupled lattice and improve the complexity and security of the chaotic system. In the end, we use the newly designed spatio-temporal chaotic system as a pseudo-random generator to design a new image encryption scheme. In this paper, we present a security proof for the newly proposed spatio-temporal chaotic system and image encryption scheme. Furthermore, security experiments demonstrate that the spatiotemporal chaotic system and image encryption scheme presented in this paper exhibit improved uniform distribution, absence of chaos degradation or predictability issues while offering randomness suitable for engineering applications.

Privacy protection and message authentication issues in VANETs have received great attention in academia. Many authentication schemes in VANETs have been proposed, but most of them are based on classical difficult problems such as factorization in RSA setting or Elliptic Curve setting and are therefore not quantum resistant. If a quantum computer becomes available in the next few decades, the security of these schemes will be at stake. This paper presents a vehicular lattice-based direct anonymous attestation (V-LDAA) scheme adopting an optimized signature scheme based on automorphism stability which achieves postquantum security. A distributed pseudonym update and vehicle revocation mechanism based on the lattice is introduced in this paper, which means vehicles can update their pseudonyms and revoke the identity certificate by themselves without the need for pseudonym resolutions or CRLs checking. Compared with the existing lattice-based attestation schemes in VANETs, computation costs during signing and verification operations in V-LDAA are no longer related to the number of users, which makes it suitable for large-scale VANETs. Security analysis shows that V-LDAA resists TPM theft attacks and provides users with user-controlled anonymity, user-controlled unlinkability, and unforgeability against quantum adversaries. Experimental results show that V-LDAA reduces the blind signature size by 18%. The speed of blind signing is increased by 30%, and blind verification operation is accelerated 3 times compared with the existing lattice-based direct anonymous attestation (LDAA) scheme.

In this study, a novel reversible data hiding (RDH) in encrypted domain scheme for coding channel based on sliding‐block segmentation and adaptive steganography is proposed. The proposed scheme enriches the residual information with as little additional encryption information as possible to improve the testing error rate of a steganalyser by sliding‐block segmentation with bit stream encryption. The specific encryption process effectively weakens the correlation between the adjacent pixels and minimises the size of key stream bits. The encryption key can be further embedded in the channel code stream before transmitted in the channel. Experimental analysis shows that the image encrypted by the proposed RDH scheme can achieve a peak‐signal‐to‐noise ratio of >50 dB, as the payload is 0.5 bits per pixel (bpp). In terms of security performance, compared with the state‐of‐the‐art methods, their method has a higher testing error rate when the steganalyser is utilised. Even if the payload is 0.5 bpp, the testing error rate is >0.25.