VeriSimplePIR

This library was tested on Ubuntu 20.04.6 LTS on a machine with an Intel i7 core and 32 GB of RAM.

Building the Library

Requirements

• clang++ (tested with version 10.0.0-4ubuntu1)
• OpenSSL (used to run SHA)

To install all requirements on a fresh installation of Ubuntu 20, run the following command:

sudo apt install make clang libssl-dev

Instructions

The library binary will be placed by default in ./bin/lib. The directory ~/VeriSimplePIR/bin/lib should be in your LD_LIBRARY_PATH environment variable, or you should manually place the binary in a directory that's in this variable. If VeriSimplePIR is cloned in your home directory, running this command or adding it to your .bashrc and reloading your terminal will add ~/VeriSimplePIR/bin/lib to your LD_LIBRARY_PATH environment variable.

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:~/VeriSimplePIR/bin/lib

Assuming the requirements are present, the library can be built by simply running make in the top directory.

The executable files are located in the bin/demo directory. To execute a basic test, run ./bin/demo/test/pir_test from the top directory. This will run the following four tests with a 1 MiB database:

1. Semi-honest PIR (SimplePIR).
2. VLHE PIR.
3. VeriSimplePIR without the proof generation. This is functionally equivalent to the first test, but it uses the VeriSimplePIR class.
4. Full VeriSimplePIR test.

Running the Benchmarks

Compile-time Parameters

There are three compile-time parameters that can be set to alter the performance of the benchmarks. Setting some of these values incorrectly will result in insecure parameters or benchmarks that fail to run.

• Elem: This parameter is defined in src/lib/pir/mat.h. This parameter determines the datatype used throughout the PIR protocol. The only values of this parameter that have been tested are uint32_t and uint64_t. Setting Elem to uint32_t corresponds to an online ciphertext modulus of 2^32, while setting Elem to uint64_t corresponds to an online ciphertext modulus of 2^64. The parameter generation functions automatically take this modulus into account when selecting scheme parameters. Note that these functions may fail if VLHE tries to use 2^32 for larger databases.

• STAT_SEC_PARAM: This parameter is defined in src/lib/pir/mat_packed.h. This parameter can be changed to adjust the statistical security level of the protocol. Note that all LWE parameters are chosen to satisfy at least 128 bits of computational security.

• BASIS: This parameter is defined in src/lib/pir/mat_packed.cpp. This parameter determines the basis of the packed elements of Z_p within a machine word. The constraint on BASIS is that it cannot be less than log(p), and the optimal choice of BASIS = log(p). Note that the parameter generation scripts selects log(p) to be an integer. If BASIS is greater than log(p) for a particular benchmark, set BASIS equal to the log(p) value, run make, then rerun the benchmark. This will only affect the performance of Answer, which is the entirety of the server's online computation in SimplePIR and VeriSimplePIR.

Computation Benchmarks

The VeriSimplePIR benchmarks are contained in the file src/demo/bench/preproc_pir_bench.cpp. These can be run by building the library and running bin/demo/bench/preproc_pir_bench from the top directory.

Similarly, the VLHE PIR benchmarks are given in src/demo/bench/pir_bench.cpp and the SimplePIR benchmarks are given in src/demo/bench/simplepir_bench.cpp.

Communication Benchmarks

The parameter generation scripts take a database size (parametrized by the number of entries N and the entry bitwidth d) and compute the parameters to optimize the online communication. A script to compute the size of the messages is given in src/demo/scripts/params.cpp. This file contains the full set of flags to toggle between the various protocols as well as to add the honest digest assumption.