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Scalable Multiparty Garbling

Accompanying codebase for ePrint:2023/099.

WARNING: This is an academic proof-of-concept prototype, and is not suitable for use in production systems. The code is provided solely for reproducibility and comparisons in future works.

Contents

The repository consists of the following:

Dependencies

  • Rust >=1.70
  • Python >=3.9

To install the required python packages run: pip install -r requirements.txt.

LPN Parameters

LPN parameters can be computed using the gen_lpn_params.py script.

Usage:

# Generate LPN parameters for the MPC protocol with
# - 80 bits of computational security,
# - 40 bits of statistical security,
# - 2^{-2} bias for the Bernoulli error distribution, and
# - computing over GF(2^{18}).
python gen_lpn_params.py 80 40 2 262144

# Use the --help option for more details.

Semi-Honest Secure Protocol

The repository supports computing the following benchmarks for the semi-honest secure garbling protocol:

  • Runtime and communication costs for the pre-processing phase
  • Runtime and communication costs for the garbling phase
  • Size of the pre-processing material

All benchmarks can be run independent of each other. The only caveat is that benchmarking the pre-processing phase requires generating the appropriate binary super-invertible matrix which can be done using the gen_binary_supmat.py script. The repository already includes binary super-invertible matrices for parameters used in the evaluation section of the paper.

For ease of usage, the repository also includes Briston Fashion MPC circuit descriptions of some common circuits in data/circ.

Usage:

# --- Run unit tests ---
cargo test --release

# --- Build binaries ---
cargo build --release

# --- Setup ---
# The tmp directory will be used to store temporary log files.
mkdir data/tmp
# The out directory will be used to store the outputs of benchmarks.
mkdir data/out

# Going forward, we will be using the following protocol parameters in our
# examples:
# - Number of parties (n): 16
# - Corruption threshold (t): 5
# - Packing parameter (l): 3
# - LPN key length (L): 3
# - LPN ciphertext length (Q): 5
# Moreover, we will use the 64-bit subtraction circuit in our examples. All
# binaries and scripts support the '--help' option for more details on how to
# change parameter values and inputs for the benchmarks.

# --- Generate binary super-invertible matrix ---
# The script takes the ratio of total number of parties to number of corrupt
# parties as an argument. Ensure that the maximum number of corruptions, as
# output by the script, is at most the parameter 't' and the output minimum
# number of honest parties is at least 'n - t'.
#
# NOTE: The repository already contains binary super-invertible matrices for 
# some parameter values.
python scripts/gen_binary_supmat.py 16 3 --output_path ./data/binsup_mat

# --- Benchmark pre-processing phase ---
# The pre-processing phase can be benchmarked by running an instance of the
# 'preproc' binary with appropriate arguments for each party. In addition to
# the protocol parameters, the binary also requires a network file listing the
# address of each party; an example of which can be found at
# './data/localnet.txt'.
#
# The '--save' option can be used to save the benchmark stats for all parties
# in a single JSON file. The file will be created by the party with ID 0.
#
# When running all parties on a single machine, the 'run.sh' script automates
# running the binary for each party. The script only runs party 0 in the
# foreground, all other parties are run as background tasks. The output of all
# parties is available in 'data/tmp'.
./run.sh ./target/release/preproc 16 --net ./data/localnet.txt \
    --threshold 5 --packing-param 3 --binsup-mat ./data/binsup_mat/n16_t5.txt \
    --lpn-key-len 3 --lpn-mssg-len 5 \
    --circ ./data/circ/sub64.txt \
    --reps 3 --threads 2 --save ./data/out/preproc.json

# --- Benchmark garbling phase ---
# The garbling phase can be benchmarked by running an instance of the 'garble'
# binary with appropriate arguments for each party. As in the case of
# pre-processing, the binary also requires a network file listing the address
# of each party.
#
# As in the case of pre-processing, the '--save' option can be used to save the
# benchmark stats for all parties in a single JSON file created by the party 
# with ID 0.
#
# In the example below, we use the 'run.sh' script to run all parties on the 
# same machine.
./run.sh ./target/release/garble 16 --net ./data/localnet.txt \
    --threshold 5 --packing-param 3 \
    --lpn-key-len 3 --lpn-mssg-len 5 \
    --circ ./data/circ/sub64.txt \
    --reps 3 --threads 2 --save ./data/out/garble.json

# --- Size of pre-processing material ---
# The size of the pre-processing material can be obtained using the 'preproc_size'
# binary.
./target/release/preproc_size --circ ./data/circ/sub64.txt \
    --num-parties 16 --threshold 5 --packing-param 3

NOTE: Generating and encoding the public LPN matrix can significantly delay the time to start running the benchmarks for the garbling phase. This is a one-time computation and does not affect the runtime and communication cost of the garbling phase. For the purpose of benchmarking, the benchmarks branch avoids this one-time overhead by re-using the same LPN matrix while keeping the garbling phase protocol identical. We recommend either serializing and storing the encoding of the LPN matrix or using the benchmarks branch when benchmarking over different sets of parameters.

Maliciously Secure Protocol

The communication cost and the computation cost of the maliciously secure garbling protocol can be estimated using the communication_estimates.py and computation_estimates.py scripts respectively. The computation estimates rely upon the time required to carry out individual field operations. These timings can be obtained by running cargo bench (which in turn uses criterion) as shown below, which benchmarks the performance of the Fast Galois Field Arithmetic Library, also used in the implementation of the semi-honest secure protocol.

Usage:

# --- Estimate communication costs ---
# Communication costs can be estimated using the 'communication_estimates.py'
# script. The script takes the number of input wires, AND gates and XOR gates
# as argument along with other protocol parameters. For the purpose of
# estimation, any inversion gates can be considered as XOR gates (since the
# latter are more expensive). Use the '--help' option for more details.
#
# In the example below, we estimate the communication cost for garbling AES-128
# with 128 parties, tolerating a corruption threshold of 31 and with the
# packing parameter set to 33.
python scripts/communication_estimates.py -n 128 -t 31 -l 33 256 6400 30263

# --- Estimate computation costs ---
# Computation costs can be estimated using the 'computation_estimates.py'
# script. The script takes the number of input wires, AND gates and XOR gates
# as argument along with other protocol parameters. For the purpose of
# estimation, any inversion gates can be considered as XOR gates (since the
# latter are more expensive). Use the '--help' option for more details.
#
# In the example below, we estimate the computation cost for garbling AES-128
# with 128 parties, tolerating a corruption threshold of 31 and with the
# packing parameter set to 33, where each party uses 2 threads.
python scripts/computation_estimates.py -n 128 -t 31 -l 33 --threads 2 256 6400 30263

# --- Benchmarking field operations ---
# As discussed earlier, the estimation of the computation costs rely on the
# time required to carry out individual field operations. These can be obtained
# using the command below and used with the script using the '--time_add' and
# '--time_mult' options. The default values in the script correspond to
# benchmarks computed using the evaluation environment described in the paper.
cargo bench