## 1 Introduction  
Digital technologies have transformed media content production and distribution in the global entertainment and media industry over the last two decades. Many challenges still remain, though, especially relating to the way in which digital content can be distributed on the Internet, and how content contributors are compensated when their materials are used or bought through legitimate channels. One of the latest experiments in this specific industry involves the use of blockchains and cryptocurrencies for micropayments--payments by consumers of very small sums of money to access specific content. Blockchain technology and cryptocurrencies can provide an ideal, cost-effective framework for payments, preserving privacy, with low commission fees and instant financial transactions without intermediaries.  
The blockchain could also store instructions, in the form of a smart contract, for how the content creators would be compensated for the song or music, and how the users can access it. The innovative features that can be offered with blockchain technology are, among others, the ability to have highly personalized services, whereby user IDs, profiles, preferences and history will be present whenever needed by the users and for every media content that is created, consumed, shared, recommended or further analyzed, and the sustainability of media content and services since the blockchain technology can ensure a long-lasting, scalable and disruptive revenue-based business model that can enhance the financial and technical sustainability of media and services.  
The blockchains rely on digital signatures (based on cryptography) to define the identities of the participants in the network. In the Bitcoin network, for instance, the wallet ID is the one which defines the identification of the participant and, through this, someone can search for specific transactions and interact with him/her. Creating a digital ID, combining the decentralized blockchain principle with identity verification, would act as a digital watermark, assigned to every online transaction. This would allow organizations to check identity on every transaction in real time, virtually eliminating fraud. Blockchain's decentralized approach can give control back to users, preventing fraud and boosting trust in the process. However, the blockchain approach on identity management is rather narrow in scope as it does not provide full-flavored identity management functionality and possibilities to interact with third party off-chain services. This is a research topic which is handled in the current paper.  
Know Your Customer (KYC) processes strongly rely on identity management, and provide the backbone of organizational and financial institutions' anti-money laundering efforts. Especially, to date, with many applications in financial technology being implemented on blockchains, KYC processes will have to play a significant role in trying to couple valid identity management with privacy-preserving techniques in order to be able to be in compliance with regulations such as General Data Protection Regulation (GDPR). This area of research is the main focus of the paper. In particular, the motivation of the current research is to design and implement new, efficient and effective KYC processes which will run in a decentralized mode over blockchains. For this reason we design an overall architecture which makes use of highly decentralized technologies such as InterPlanetary File System (IPFS) and Quorum blockchain that allows, through the suggested developed smart contracts, the implementation of multi-party KYC processes on top of blockchains. The specific implementation along with the description of the use case through which it has been validated has been part of the Bloomen project which is described briefly in the following.