sylvainpelissier / INDCPAD_HE_ThresFHE

INDCPAD_HE_ThresFHE

This is a git repository that implements the IND-CPA-D attacks introduced in Attacks Against the IND-CPAD Security of Exact FHE Schemes written by the following authors:

Jung Hee Choeon (SNU & Crypto Lab Inc.)

Hyeongmin Choe (SNU)

Alain Passelègue (CryptoLab Inc.)

Damien Stehlé (CryptoLab Inc.)

Elias Suvanto (CryptoLab Inc.)

KRD experiments

This folder contains 5 folders concerning TFHE:

• TFHE-rs library: An implementation of TFHE (available at https://github.com/zama-ai/tfhe-rs, commit ad41fdf5a5060c0a981cd0c35bf998feafe68e02).
• collect_TFHE_ciphertexts: Rust code using TFHE-rs to run the oracle side.
• collected_samples: Outputs from the above (specifically, from the custom parameter).
• TFHE_KRD: Python code reading the samples (failed ciphertexts) and guessing the secret key. This is the KRD adversary side.
• Simulation folder to generate samples faster and for parameter sets with low decryption failure probability.

and 2 folders about BFV KRD:

• OpenFHE library: An implementation of many FHE schemes, in particular, BFV (available at https://github.com/openfheorg/openfhe-development, commit 4ebb28ea7bdd894a73bc5b73e59fcfbc7825330).
• BFV KRD: CPP code recovering the secret LWE error.

How to generate legitimate ciphertexts that fail to decrypt

There are two options:

• Running a TFHE library: Run cargo run --release > ../collected_samples/failed_ctxt.out inside the collect_TFHE_ciphertexts folder. It will run the paper TFHE KRD collecting part using the TFHE-rs library. It will use the 128-bit IND-CPA secure custom parameters. It will then put the collected ciphertexts as a text file in the collected_samples folder
• Simulating using rejection sampling: Run python3 simulate_TFHE_ciphertexts/main.py > ../collected_samples/sim_failed_ctxt.out to generate incorrect ciphertexts using a rejection sampling technique on the conditioned distribution detailed in the paper.

How to run TFHE-KRD

Run python3 TFHE_KRD/main.py < collected_samples/failed_ctxt.out. It will read the samples using py_stdin.py, call KRD.py on them to guess the secret key and compare it to the real secret key.

How to run BFV KRD

The C++ code is available and makes a call to the OpenFHE library. It returns the secret LWE error.