FULLY HOMOMORPHIC ENCRYPTION CALCULATION TOOLS

Authors: Eloi Besnard, Tiphaine Henry

Can perform addition, subtraction, multiplication, max and division with homomorphic encrypted data using TFHE library. See more explaination on my work at https://www.osgood-on-the-web.ml/cryptography/1. See more explaination about FHE at https://www.zama.ai/post/tfhe-deep-dive-part-1.

Usage

Run make.
If problems, see Notice.

• I. [CIPHERING]
  call alice with the numbers you want to cipher.
  Say you want to multiply 67 times 8 times 6, run: ./alice 67 8 6

• II. [COMPUTING]
  call cloud to choose the computation you want to do. Dont forget to tell the number of inputs.
  Here is the format: ./cloud <number of inputs> <choice of computation>
  Choice of computation is the following:

   - 1: multiplication
   - 2: division (only works with positive integers)
   - 3: addition
   - 4: subtraction
   - 5: max
  

  In our case, we want to multiply 3 inputs so: ./cloud 3 1

• III. [DECIPHERING]
  Then, once cloud is done, run verif to decipher the data: ./verif

TODO:

• need to pass as argument the number of bits we want to perform computation with.
• problem of MSB used for MUX
• make anything using MUX work with negative integers

NOTICE

First, make sure that TFHE is installed, and that your environment variables contains the necessary information to find TFHE include directory and library directory.

During the compilation, CPLUS_INCLUDE_PATH and C_INCLUDE_PATH should contain /usr/local/include and LIBRARY_PATH and LD_LIBRARY_PATH should contain /usr/local/lib. During the execution of a program that uses TFHE, only the variable LD_LIBRARY_PATH is needed.

You can put the following lines to your .bashrc or .profile config file to make the changes permanent.

TFHE_PREFIX=/usr/local
export CPLUS_INCLUDE_PATH=${TFHE_PREFIX}/include:${CPLUS_INCLUDE_PATH}
export C_INCLUDE_PATH=${TFHE_PREFIX}/include:${C_INCLUDE_PATH}
export LIBRARY_PATH=${TFHE_PREFIX}/lib:${LIBRARY_PATH}
export LD_LIBRARY_PATH=${TFHE_PREFIX}/lib:${LD_LIBRARY_PATH}

Then, to compile one of the tutorial program, just pass -ltfhe-spqlios-fma during the linking phase. For instance:

gcc alice.c -o alice -ltfhe-spqlios-fma
gcc cloud.c -o cloud -ltfhe-spqlios-fma
gcc verif.c -o verif -ltfhe-spqlios-fma

If you do not have the spqlios-fma version, replace with one of the version of TFHE that you have installed (-ltfhe-nayuki-portable, -ltfhe-nayuki-avx, -ltfhe-fftw, or -ltfhe-spqlios-avx).

You can have a look at the Makefile for other compile options!

Happy coding!