# A Blockchain Self-Sovereign Identity for Open Banking Secured by the Customer's Banking Cards
## 1 Introduction  
In the modern transformation of digital banking, the customer does not have control of the sharing of their personal and financial data with the increasing number of authorized financial service providers. Open finance [1] is an emerging field within open banking, in which financial institutes, regulated websites, and financial applications obtain access to transactional details, for example, customer financial data such as savings, insurance, and customer credit (or part of it) from the user's bank accounts and payment services, usually via the Application Programming Interface (API) and based on customer consent. The purpose is to not only recommend cheaper services, but also to provide advice and customized product recommendations, similar to open banking but with a kind of'read' data permission [2]. Open finance comes with 'write' permissions to execute cost savings on behalf of the customer, for example, transferring an additional USD 150 to the user's saving account with the aim of tailoring the best financial decision for the customer. The banking sector has a significant stake in the digital trust era, including via customers' personal data, Know Your Customer (KYC) procedures, policy regulations, and secure authentication. There is a strong potential for banks to invest in identity management and expand payment card services and digital payment credentials with digital identity capabilities based on the strong position of trust and security measures. Banks, as identityactors, can act as an identity issuer, deliver digital identity services, and provide credentials and authentication services. In such a sensitive data-sharing context, many challenges appear, such as banks trying to adapt to a higher volume of transactions, data polices, and governmental regulations to ensure proper security and privacy controls for users to manage their own data between financial pillars. To avoid privacy leakage in such a paradigm, recalling for instance the Facebook-Cambridge Analytical data scandal [3], customers want to control and grant permission to each sharing transaction. In our proposed prototype, SSBI provides self-sovereign identity (SSI) features based on Veramo version 3 APIs [4] and strengthens the security of managing customer private keys using industry-trusted banking cards, and related form factors, assuming at least one banking account is available before the registration phase. Banks and other parties cannot share the data without permission from the customer in a decentralized framework. These data can be limited to credentials and proofs instead of disclosing the detailed personal identity of financial information. This attempts to address the issues of centralized or cloud-based identity systems, including leakage of immutability, traceability, and third-party control over individual data. In this paper, we propose a framework to enable users to control their identities and privacy in the context of open finance and open banking, using a Blockchain-based SSI platform to improve the trust between customers and involved financial parties. SSBI integrates the banking card to improve the security of signing identity creation and sharing transactions, and considers a seamless user experience. In addition, this work is validated against a typical use case scenario and possible results are discussed to evaluate the proposal in contrast to related solutions. During the demonstrated implementation, we designed and implemented an SSI framework based on the Veramo SDK with an underlying Ethereum Blockchain to extend the model, as suggested in [5]. Our contributions include the integration of the customer's banking cards to hold the identity secret keys, the signing of pairwise DIDs (Decentralized Identifiers), and verifiable proofs to balance the security and customer experience. This improves the user's trust by controlling the identity enrolment and claims of several financial services provided by open banking institutions.