Digital identity has always been considered the keystone for implementing secure and trustworthy communications among parties. The ever-evolving digital landscape has gone through many technological transformations that have also affected the way entities are digitally identified. During this digital evolution, identity management has shifted from centralized to decentralized approaches. The last era of this journey is represented by the emerging Self-Sovereign Identity (SSI), which gives users full control over their data. SSI leverages decentralized identifiers (DIDs) and verifiable credentials (VCs), which have been recently standardized by the World Wide Web Community (W3C). These technologies have the potential to build more secure and decentralized digital identity systems, remarkably contributing to strengthening the security of communications that typically involve many distributed participants. It is worth noting that the scope of DIDs and VCs extends beyond individuals, encompassing a broad range of entities including cloud, edge, and Internet of Things (IoT) resources. However, due to their novelty, existing literature lacks a comprehensive survey on how DIDs and VCs have been employed in different application domains, which go beyond SSI systems. This paper provides readers with a comprehensive overview of such technologies from different perspectives. Specifically, we first provide the background on DIDs and VCs. Then, we analyze available implementations and offer an in-depth review of how these technologies have been employed across different use-case scenarios. Furthermore, we examine recent regulations and initiatives that have been emerging worldwide. Finally, we present some challenges that hinder their adoption in real-world scenarios and future research directions.

翻译：数字身份始终被视为实现多方安全可信通信的基石。随着数字生态的持续演进，技术变革深刻影响着实体数字身份的识别方式。在数字化演进过程中，身份管理范式已从集中式转向去中心化。该进程的最新阶段表现为新兴的自主主权身份（SSI），其赋予用户对数据的完全控制权。SSI技术体系依托近期由万维网联盟（W3C）标准化的去中心化标识符（DID）与可验证凭证（VC），这些技术有望构建更安全、更去中心化的数字身份系统，显著增强涉及多方分布式参与者的通信安全性。值得注意的是，DID与VC的应用范围不仅限于个人用户，更扩展至云资源、边缘设备及物联网（IoT）资源等各类实体。鉴于该技术的新颖性，现有文献缺乏关于DID与VC在超越SSI系统的多应用域中部署情况的系统综述。本文从多维视角为读者提供此类技术的全面概览：首先阐述DID与VC的技术背景；进而分析现有实现方案，深入评述这些技术在不同应用场景中的部署实践；同时考察全球范围内兴起的最新法规与推进计划；最后揭示其在现实场景中推广面临的挑战及未来研究方向。