The cryptographic hash is stored on the Ethereum network using Web3j by interaction through a smart contract.

Store credentials on IPFS which is a peer to peer decentralized file storage system.

Every time user adds a credential, a cryptographic hash is generated for that specific set of credentials. On adding another set of credentials, the previous hash is destroyed and a new hash is generated which only you can know.

A minimalistic UI that focuses only on the functionality and no extra stuff to confuse the user.