Privacy-Preserving Distributed Algorithm for Sparse Vector Sum (Report‪)‬

1 Introduction Suppose there is a neighborhood with two local banks. Many of the college students in the neighborhood need to apply for student loans to support their study, and both of the two local banks provide student loans. However, the banks would like to make sure that each student gets no more than ten thousand dollars in total for loans from both of them. Clearly, this would be a trivial problem if the two local banks were allowed to exchange private information about their customers, like how much a specific student has got from each of them. However, customers do not want their banks to reveal their private information to anybody, including to the other local bank. Can we solve this problem in a privacy-preserving way?