# A Blockchain Self-Sovereign Identity for Open Banking Secured by the Customer's Banking Cards
## 3 Related Work  
KYC2 Kyla (2014) is a framework for client onboarding based on the SSI model and Hyperledger Indy (2013). The model was discussed in terms of the SSI concept and General Data Protection Regulation (GDPR) (2014) rules. It advised the need for key management to secure the secret agent keys and recovery conditions. This work proposes using banking smart cards for cryptographic operation handling and deploys the SSI concept based on Ethereum Blockchain; specifically, the curve exists for several market banking Java Cards and was validated in our proof of concept. The authors in [20] provide a survey and overview of the SSI concept and available solutions in terms of the architecture and actors in the approach to identifier-registry and claim-registry models. Blockchain enables these decentralized registries, although it is not a necessity, and the storage of both identity and claim registries can also be decentralized. The paper presents on-chain and off-chain storage with the advantages and disadvantages for each option. In our work, we store private information off-chain while the integrity and authenticity proofs are stored on-chain. SCARAB [21] is a model used for decentralized and secure access control, in which the accountability issue of SSI Blockchain-based systems is resolved by registering every data access request in public mode. It introduced on-chain secret verifiable sharing to collective management using the Byzantine protocol, and also introduced identity skipchains to control access policies to manage the identity and enable user's self-sovereign identity management [21]. SCARAB stores everything on-chain, which affects the scaling and performance, making sensitive identity data available for the public, and meaning that it is not possible to erase it. BBM [5] is a Blockchain-based SSI model for open banking and enables secure communication between involved parties. In contrast to BBM, it is proposed here to use the banking card, which is trusted and conveniently used by customers for daily purchases, to act as tamper-resistant storage for the identity private key, and to perform the cryptography required for verifiable credential issuance and sharing with banks and third-party agencies. Instead of relying on additional devices, such as hardware tokens, we utilize the banking card to balance security and usability. This work proposes the implementation of a prototype to assess the feasibility and possibility of integration with the existing payment card issuance flow. The SSI framework has been used to prevent banking scam calls [7]. The authors proposed an SSI model based on Hyperledger Indy [6] and utilization of the user's banking card with the aim of preventing banking scam calls. In contrast, in our framework, we leverage the use case and overcome the limitation of the signing curve on Java Card ED25519, which is required for Indy transactions. The proposed framework is based on Veramo, which relies on Ethereum Blockchain, where the required SECP256K1 signing curve exists for several banking cards used for this work, to issue ethr DIDs and VCs. This fits within the open banking use case; the proposed framework allows smart contracts that automate several online financial services. In [22], the authors proposed a protocol to reach a high level of assurance (LoA) for a mobile-phone-based SSI identity wallet with the main focus on achieving a high LoA. It considered key tamper-resistant storage requirements to achieve the high LoA via combining a software wallet key part and a YubiKey 5 Ci token [23] for the hardware key part. This protocol is applicable for our implementation, since we rely on the banking card for the tamper-resistant storage of the key materials to secure the SSI wallet instead of the mobile secure element, which does not exist in some market mobile devices. In contrast, in our work we leverage the banking use case and balance the usability and strong security without relying on an additional device for banking customers.