# Two-Party Function Computation on the Reconciled Data

## TL;DR

This paper explores the problem of computing functions on reconciled data from two users, establishing communication lower bounds, connecting to related problems, and proposing a hash-based protocol for sum computation.

## Contribution

It introduces the study of function computation on reconciled data, derives communication complexity bounds, and presents a new hash-based protocol for sum functions.

## Key findings

- Deterministic protocols for sum and product require exponential communication in worst case.
- Connections to set disjointness and intersection problems provide additional bounds.
- A hash-based protocol for sum computation is proposed and analyzed.

## Abstract

In this paper, we initiate a study of a new problem termed function computation on the reconciled data, which generalizes a set reconciliation problem in the literature. Assume a distributed data storage system with two users $A$ and $B$. The users possess a collection of binary vectors $S_{A}$ and $S_{B}$, respectively. They are interested in computing a function $\phi$ of the reconciled data $S_{A} \cup S_{B}$. It is shown that any deterministic protocol, which computes a sum and a product of reconciled sets of binary vectors represented as nonnegative integers, has to communicate at least $2^n + n - 1$ and $2^n + n - 2$ bits in the worst-case scenario, respectively, where $n$ is the length of the binary vectors. Connections to other problems in computer science, such as set disjointness and finding the intersection, are established, yielding a variety of additional upper and lower bounds on the communication complexity. A protocol for computation of a sum function, which is based on use of a family of hash functions, is presented, and its characteristics are analyzed.