Abstract: SNAP (Standar Nasional OPEN API Pembayaran) is an
implementation of open banking for encouraging digital transformation in
the banking industry. SNAP was submitted by several sub-working groups
formed jointly by ASPI and the Bank of Indonesia. In the document
Pedoman Tata Kelola (Bank of Indonesia, n.d.), a customer data protection
mechanism exists between the bank, the owner of Open API, and the user
of Open API. However, there is no data protection process carried out by
consumers so third parties, that use the Open API of the bank, do not need
to know the customer's data. Based on the web3 with zero-knowledge
proofs protocol, users can store data and transmit only in encrypted form
which can only be opened by calculating the data with a pre-agreed smart
contract. Banks can work like a decentralized network on web3, where the
process of calculating proof and witness is carried out by the bank. Proof
and witness are calculated using a zero-knowledge proof protocol, making
duplicating difficult. For this reason, we propose a new architecture using
smart contracts between banks and customers using the ZK-SNARK
method using gnark library in the Golang programming language.
Therefore, there is no significant performance difference between using
ZK-SNARK and without ZK-SNARK in the API call process.

Keywords: data protection, gnark, SNAP, zero-knowledge proofs, ZK-
SNARK