Privacy-preserving overdraft management using blockchain technology

A computer program product for managing user overdrafts in a privacy-preserving manner, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor associated with a computerized system to cause the computerized system to perform a method comprising:

• issuing a first overdraft token computed based on a user identifier of a given user, an initial overdraft value, a first serial number, and an encryption key that is shared with the given user;
• generating a first zero-knowledge proof of that said initial overdraft value is equal to a maximal value of credit granted to said given user;
• computing an overdraft transaction based on the first overdraft token and the first zero-knowledge proof and signing the computed overdraft transaction using a secret key that is not shared with the given user;
• and
• submitting the overdraft transaction to a blockchain.