# Feldman Verifiable Sum

## Introduction

Verifiable secret sharing mechanism is an efficient and practical secret
sharing mechanism. Feldman Verifiable sum is a multi-party private data
summation module based on verifiable secret sharing.This component can
sum the same feature of common users among different participants
without exposing private data.（This module is still in the research stage, has not yet been put into production）

Here, three participants of the federation process is given, Party A
represents Guest, party B and party C represent Host. The process of
Feldman Verifiable Sum is shown below:

![Figure 1: Process of Feldman Verifiable Sum](../images/feldman_verifiable_sum.png "Figure 1: Process of Feldman Verifiable Sum")
***Figure 1:*** *Process of Feldman Verifiable Sum*


![Figure 2: Process of share sub-key](../images/share_sub-key.png "Figure 2: Process of share sub-key")
***Figure 2:*** *Process of share sub-key*

In the process shown above, each party encrypts its own secret value,
share sub-key, recieve sub-keys from other parties, and then combine all
these sub-keys. Guest, as the task initiator, initialize the parameters
and decrypt the sum result.

## How to Use

In general, this component can be used in the data preprocessing stage
to count some features. It supports integers and floating-point numbers
from - 2 ^ 63 to 2 ^ 64. By default, the maximum precision is set to 6
decimal places.

## Param

::: federatedml.param.feldman_verifiable_sum_param
    rendering:
      heading_level: 3
      show_source: true
      show_root_heading: true
      show_root_toc_entry: false
      show_root_full_path: false

## Features

1.Supports summation of floating-point numbers and negative numbers

2.Attacks can be detected when the malicious participant is less than
(n-1)/2

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## Examples

{% include-examples "feldman_verifiable_sum" %}
-->