Introduction

famodulus-client is a JavaScript library for outsourcing modular exponentiations (modexps) in multiplicative groups with prime modulus. It is based on the research conducted in Efficient and Secure Outsourcing of Modular Exponentiation.

Outsourcing is performed using a RESTful API with one or more servers (depending on the algorithm). Have a look at famodulus-server for a working implementation or have a look at the API description.

The current version of the library supports the following outsourcing algorithms:

• Direct outsourcing without any blinding
• Blinding of the exponent by using a simple, algebraic decomposition (2 servers required)

See also mainini/famodulus for a complete modexp outsourcing system containing this library as well as the server and a corresponding demonstrator application.

This implementation makes extensive usage of various ES6 features and can be used in a reasonably current browser (tested with Firefox 50.1) or in node.js (>=6.9.1).

WARNING: This library is intended exclusively for research purposes and must not be used in any real applications with any security requirements. You have been warned.

Installation

To install the library and its dependencies for usage in node.js as well as for building it for the browser, an installation of node.js with version 6.9.1 or later is required. After building, the library can be used in the browser without any further dependencies.

Web Browser

The code of the library is organized as a CommonJS module which is automatically transformed into a single file for usage in the browser during the installation process. To use the library, check out this repository (if you haven't already), then run the installation process:

npm install

After installing all dependencies, the library as well as its documentation should have been generated in the .build directory. The file .build/js/famodulus.browser.js contains everything needed and can be loaded directly into the browser.

node.js

famodulus-client is currently not published on npmjs.org. To use the library in node.js, simply clone it to the node_modules directory of your choice (application or global), then start to use it straight away (see below).

Usage

Interaction with the library occurs through a FamodulusClient object which offers methods for all supported algorithms:

var FamodulusClient = require('famodulus-client');
var client = new FamodulusClient(['server_1', 'server_2']);
...
client.decExponent(modexps)
...

Documentation of FamodulusClient and all related code can be found in .build/doc/module-famodulus-client_client-FamodulusClient.html after installation. Good usage examples can be found in test/client.js or in the famodulus-demo.

Version History

1.1.1 (2017-02-08)

• Linking thesis in README

1.1.0 (2017-02-02)

• Large performance improvement due to new BigInteger conversion functions
• Abstraction of BigInteger library in own module

1.0.1 (2017-01-14)

• Bugfix: randomList() - random value must be < 1
• Bugfix: non-prime modulus in unit test causing the test to fail sometimes
• Improvement: Better performance with mod() and simpler testing in random()
• Improvement: Not shuffling lists of size <= 1

1.0.0 (2017-01-11)

• Initial version
• Supporting direct outsourcing and basic exponent decomposition