Fully Homomorphic Encryption

Overview

This is a simple client-server calculator which uses the Fully Homomorphic Encryption scheme described in Gentry (2008). The scheme allows the server to performs arbitrary arithmetic operations without ever knowing what the values of the operands are.

If you are only looking for the libfhe library itself, check out the lib branch of this repository. See the wiki pages at https://github.com/rdancer/fhe/wiki/_pages for more detailed information on this project.

Note: This project was the first publicly available implementation of the encryption system described in Gentry (2008). You are more than welcome to fork it or contribute patches, however, please consider using e.g. the https://hcrypt.com/ project instead.

In particular, this demo is unfinished, and, because when it was developed, NaCl was a new technology, with changing API, some work may be required to make it work in contemporary versions of Google Chrome.

Project Structure

This project is split between four interdependent modules:

1. The libfhe library, written in C
2. A Native Client (NaCl) plugin, written in C++; uses the libfhe library; compiles into several binary files: one per each supported architecture.
3. A directory with files to be served by a normal HTTP server such as Apache. Written in HTML, JavaScript, CSS, etc. The compiled NaCl binaries must be copied here.
4. Custom XML-RPC server; uses the libfhe library

Each individual sub-project contains a Makefile, which automates most of the work. However, some manual copying and configuration must still be performed; some of the required steps may not be documented.

Files

libfhe/
  The `libfhe` library source.  Corresponds to the contents of he `lib`
  branch of this repository.

nacl/sdk/
  Please download the *NaCl* SDK and unpack it into this directory

nacl/sdk/examples/fhe_calculator/
  Source of the *NaCl* plugin

www/
  Files to be served by the web server.  The *NaCl* compiled files must
  be copied here manually.

xml-rpc/
  Source code of the FHE evaluator XML-RPC server

contrib/
  Third-party libraries and code

Fully Homomorphic Encryption: Calculator Demo.png
  Screenshot of how the calculator looks when working

README.md
  This file

Normal Operation

1. A Native-Client-capable web browser (such as Google Chrome [Note: the project may need to be updated to work with contemporary browsers]) connects to the web server, the client downloads the NaCl binary appropriate for the CPU architecture it is running on. The UI is initialised.
2. User enters an arithmetic formula and presses the Calculate button
3. Web browser pre-processes the formula, and sends it (encrypted) to the XML-RPC server
4. XML-RPC server, computes the result, and sends it (still encrypted) back to the web browser
5. Web browser decrypts the result, shows the result to the user, and updates the UI accordingly

The libfhe library handles the encryption, decryption, and operations on the encrypted numbers. The XML-RPC server, while being able to perform operations on the numbers, will have no knowledge of their value.

Legal Stuff

Copyright 2010, 2013 Jan Minar [email protected]

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 (two), as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

References

Gentry, Craig: Computing Arbitrary Functions of Encrypted Data (2008), URL: http://crypto.stanford.edu/craig/easy-fhe.pdf