Traditional industries rapidly transcend the time and place restrictions of the country according to the technology growth by leaps and bounds over the year. Regrettably, international cybercrime incidents simultaneously explode by 2,400 million from 2020 to 2021. Undoubtedly, the real-time incident response has become the primary subject of incident handling. In this article, we aim to propose lawful remote forensics mechanism for ensuring the optimal protection of potential evidence in stochastic and unpredictable transnational crime. Meanwhile, the entire process can be performed remotely and compliant with legal requirements, such as ISO/IEC and NIST regulations. Specifically, all the procedures can be retroactive based on the design of the chain of custody, which leads to the proof of evidence admissibility. Aside from the security essential confirmation by the formal tools Proverif, AVISPA, and Scyther, simulation results have demonstrated that remote forensics can fulfill the legal requirements and perform excellently in various incident scales.

Cloud storage services are widely used across the world. Cloud storage services can be virtualized, decentralized, they are also can be access by mobile phones. That is a great challenge to traditional digital forensics. In this paper, we focus on the most popular cloud storage services, and choose the iOS system as platform. Our experiments show what kinds of data remnants can be found. We also presented how the digital investigators to view the contents, even the original files cannot be recovered.

Given the high frequency of information security incidents, feeling that we may soon become innocent victims of these events may be justified. Perpetrators of information security offenses take advantage of several methods to leave no evidence of their crimes, and this pattern of hiding tracks has caused difficulties for investigators searching for digital evidence. Use of the onion router (Tor) is a common way for criminals to conceal their identities and tracks. This paper aims to explain the composition and operation of onion routing; we conduct a forensic experiment to detect the use of the Tor browser and compare several browser modes, including incognito and normal. Through the experimental method described in this paper, investigators can learn to identify perpetrators of Internet crimes, which will be helpful in future endeavors in digital forensics.

International audience

Multimedia hiding system is to embed message behind the specified media, but it is still kept normal in media representations via human sensitive organizations without causing imperceptibility. In this article, we propose a data hiding system by means of flexible exploiting modification directions to achieve safer message concealments in image-media. In our scheme, n cover-pixels are flexibly chosen on modulo operations to embed a secret s , where n = ⌈ log 3 ( s ) ⌉. The varied pixel values associated with the chosen n pixels are only changed among [-1, 1]. Because the numbers of adjustable pixels are much greater than the pixels in the past scheme, our scheme is able to obtain a higher embedded ratio in response to the capacity requirements of information hiding systems. In addition, we also applied the statistics-steganalyzers to demonstrate that our scheme has accomplishment not only higher capacity but also kept the robustness against the blind steganalyzers.

Recent advances in pervasive computers, networks, telecommunication, and information technology, along with the proliferation of multimedia-capable mobile devices, such as laptops, portable media players, personal digital assistants, and cellular telephones, have stimulated the development of intelligent and pervasive multimedia applications in a ubiquitous environment.Due to constant changing environments, Mobile multimedia implies considerable challenges to operators, infrastructure builders in terms of ensuring fast, reliable services and accommodating the quick growing global customer needs.This special issue aims to foster the dissemination of high quality research in any new theory and technique and to present future directions regarding multimedia and mobile computing.This special issue welcomes papers focused on all topics ranging in the wide spectrum of multimedia and mobile computing with emphasis on theoretical aspects as well as practical frameworks and implementations.Overall, the special issue will outline the recent trends, major challenges, and perspectives related to multimedia and mobile computing.We have received many manuscripts.Only 10 manuscripts with high quality were finally selected for this special issue.Each manuscript selected was blindly reviewed by at least three reviewers consisting of guest editors and external reviewers.We present a brief overview of each manuscript in the following.The first paper entitled "Fine-grained user access control in ciphertext-policy attribute-based encryption" by Junbeom Hur et al. propose a fine-grained user revocation scheme without affecting any non-revoked users who share the same attributes in ciphertext-policy ABE; it does not require the users to access the key authority and to update keys periodically.The proposed scheme improves the efficiency compared with previous revocable schemes and enhances the security in terms of the backward/forward secrecy on any membership changes in the ciphertext-policy ABE system.The second paper entitled "Privacy Preserving Frequent Itemsets Mining via Secure Collaborative Framework" by Kok Seng Wong et al. present the problem of privacypreserving frequent itemsets mining under distributed environment.This solution reduces the risk for central data mining and improves the efficiency of the current generic SMC solutions.Furthermore, this solution is more reliable and flexible regardless of the number of parties involved.

Cancer is usually treated with surgery and probably with chemotherapy or radiation. A medical malpractice of breast cancer has become an urgent need to clear the mess based on technical, workable strategy. The paper tries to: (i) understand a general diagnosis, (ii) pay attentions on how to improve the right judgments of possible misinterpretation, (iii) focus on breast cancer malpractice combined with digital medical image, (iv) present a trustworthy image based upon ADAPT principle, (v) utilize steganography concepts to assure data confidentiality, integrity, and authenticity. The physician's failure to diagnose medical images can result a patient's death, or cause enormous medical bills. A workable strategy of trustworthy computing in APAPT principle is proposed to improve the information security issue of mammography image, and establish the trustworthy computing of image diagnoses.

In order to provide large embedding capacity and to minimize distortion for the stego-image, a steganographic method using multi-pixel differencing is presented in this paper. It takes into consideration four pixels of a block, and the differences between the lowest gray-value pixel and its surrounding pixels are used to determine the degree of smoothness and sharpness for embedding the secret data. If the difference values are large in a block, and the block is located in the sharp area then more data can be embedded. On the other hand, if the block is located in the smooth area less data can be embedded. The multi-pixel differencing method is employed in our scheme. We also propose the pixel-value shifting method to increase the image quality. The experimental results show that our scheme has a large embedding capacity without creating a noticeable distortion.

In recent years, the ubiquity of communication networks speed up the development of wireless network and the Internet applications. In addition to the common service provided by the telecommunication enterprise, how to connect some distinct users to form a network which allow them to deal with their own works is a popular topic that many scholars engage in. When constructing the network, the key management is the most important problem that each system has to solve. There are many key agreement protocols which are non-hierarchical. However, the hierarchy is ubiquitous in our real life. In this paper, we have achieved a verifiable hierarchical key derivation scheme using the elliptic curve cryptography and the bilinear mapping function which can achieve the same security level but use less bit number when comparing to the RSA system.

Data hiding is a technique which embeds secret data into cover media. It is important to the multimedia security and has been widely studied. Recently, some researchers paid attention to reversible data hiding methods. These methods can reconstruct the original image from the stego-image when embedded data are extracted. In this paper, we propose a new reversible steganographic method for vector quantization (VQ) compressed images. The new method uses the hit pattern to achieve reversibility, and the hit pattern strategy successfully reduces the overhead. The codebook is partitioned by the extension method which makes the stego-image have good visual features. Also, a look-up table is used to speed up the partitioning operation. Compared to Chang et al.'s method, the experimental results show that the proposed method has higher capacity, better visual quality, and lower running time.

Cyber world is developing with substantial advancement to enter into glorious future, but cybercrime has always been a disaster to this dream. Recent advancement in internet technologies has lead stalking to become cyber. Cyberstalking offenses have become diversified and technological advance. It creates social and mental disorders among victims. In order to improve the privacy of internet users against cyberstalking, a novel examination of action research is evaluated from a former event. With the guidance of this case study, we can discriminate normal social networking friends from the possible offenders. The initial results show that our approach is highly helpful. Curbing cyberstalking is a baffling task because of its newness and technological furtherance. It is believed that this study will clarify the obscure technological and social aspects of cyberstalking. In this paper, the proposed solutions can prohibit users from the risk of getting hurts, facilitate to cut down its roots and remove its foundation.

This paper proposes a new adaptive least-significant- bit (LSB) steganographic method using pixel-value differencing (PVD) that provides a larger embedding capacity and imperceptible stegoimages. The method exploits the difference value of two consecutive pixels to estimate how many secret bits will be embedded into the two pixels. Pixels located in the edge areas are embedded by a k-bit LSB substitution method with a larger value of k than that of the pixels located in smooth areas. The range of difference values is adaptively divided into lower level, middle level, and higher level. For any pair of consecutive pixels, both pixels are embedded by the k-bit LSB substitution method. However, the value k is adaptive and is decided by the level which the difference value belongs to. In order to remain at the same level where the difference value of two consecutive pixels belongs, before and after embedding, a delicate readjusting phase is used. When compared to the past study of Wu et al.'s PVD and LSB replacement method, our experimental results show that our proposed approach provides both larger embedding capacity and higher image quality.

A secure and anonymous conference call set-up scheme is proposed for a portable cellular mobile system. The proposed scheme uses an identity-based concept and enables a mobile unit and a base station to directly authenticate each other by their public identity. It provides mobile subscribers with user identification privacy. Each mobile unit joining in this system can determine whether it is part of a conference call, but it cannot derive any further information about who else is also in the conference. That is to say, an anonymous property, accomplished through the aspect of the knapsack-like cipher mechanism, is achieved among the communicating mobiles. Furthermore, reauthentication in the course of hand-off is also discussed and the reauthentication procedure is performed through a privacy homomorphism mechanism. The time computation with an 8-bit microcontroller handset is acceptable for performing an anonymous conference call in such mobile systems. Therefore, our scheme is feasible and able to be implemented in the existing wireless exploration environment.