Detecting Fraud from Excessive Card Holdings

When a user applies for a loan from a financial institution, the financial institution needs to know the number of cards the user has opened across various financial institutions within a specified period. This helps identify suspicious telecom fraud or other risks. In this scenario, the financial institution, along with other participating institutions, uses the MPC protocol to confidentially sum the number of cards the user holds across the institutions. They can then confidentially sort this summed data to identify top-k users exhibiting suspicious high-frequency behavior.