_applied sciences_  
_Editorial_  
**Data Hiding and Its Applications: Digital Watermarking**  
**and Steganography**  
**[PERSON] 1,*(c)**, [PERSON] 2(c) and [PERSON] 3(c)  
Data hiding techniques [1] have been widely used to provide copyright protection, data integrity, covert communication, non-repudiation, and authentication, among other applications. In the context of increased dissemination and distribution of multimedia content (text, audio, video, etc.) over the internet, data hiding methods, such as digital watermarking and steganography, are becoming more and more relevant in providing multimedia security. Due to the complementary nature of general requirements of these methods, i.e., imperceptibility, robustness, security, and capacity, many data hiding schemes attempt to obtain optimal performance. There are many potential applications of data hiding techniques. Copyright protection via content proof of ownership, owner identification or transaction tracking (digital fingerprinting), broadcast monitoring, content authentication including tampering detection or localization, copy control, device control, and legacy enhancement stand out among the applications of digital watermarking. On the other hand, secret communications are the focus of steganography, either for military reasons, for dissidents, or for criminal organizations. The military and criminal applications of steganography have led to an increased interest of the academic community in steganalysis, i.e., the techniques used to detect steganographic communications. Apart from the classical applications of data hiding, mentioned above, new application scenarios have emerged in the last few years [2]. These new applications of data hiding include privacy-preserving transaction tracking, digital watermarking for data provenance, digital watermarking for forensics, network flow watermarking, network steganography, VoIP steganography, steganography for criminals and terrorists, and steganography for malware injection, among others. The goal of this special issue is to focus on the improvement of data hiding algorithms and their different applications (either the traditional or the emerging ones), bringing together researchers and practitioners from different research fields, including data hiding, signal processing, cryptography, or information theory, among others, to contribute with original research outcomes that address current challenges in data hiding methods. The list of topics/keywords covered by this special issue is the following:  
* Steganography
* Steganalysis
* Digital watermarking
* Zero watermarking
* Digital fingerprinting
* Coverless data hiding
* Reversible data hiding and applications* Forensic aspects of data hiding
* Embedding capacity/payload
* Applications of data hiding
* Ownership Proof/Copyright Protection
* Covert channels
* Traitor-tracing
* Extraction/detection
* Data integrity
* Distortion measurement
* Transform coding
* Information theory
* Information entropy
* Signal processing
* Data segmentation  
In response to the call for papers, nineteen papers were submitted to this special issue among which twelve were accepted for publication. These twelve papers include two review papers/surveys and ten contributions that address several research challenges of data hiding schemes. In one of the accepted papers, [PERSON] and [PERSON] [3] present a systematic review and future directions for blockchain-based multimedia content protection schemes using data hiding techniques. The survey provides a detailed analysis of multimedia content protection applications using blockchain and proposes a taxonomy to classify these applications based on the technical aspects of blockchain, content protection techniques, digital rights management, digital watermarking and fingerprinting, and performance criteria. The paper concludes that there is a relevant research gap regarding blockchain-based multimedia copyright protection systems. In addition, the paper discusses some technical challenges and outlines future research directions.