PyAPSI

Python wrapper for labeled and unlabeled asymmetric private set intersection (APSI).

Installation

From PyPI (builds from source)

pip install apsi

This downloads the source distribution and builds APSI + all dependencies locally. The build automatically selects the best CPU optimizations for your machine.

Requirements:

• C++ compiler (GCC >= 9, Clang >= 10, or MSVC >= 2019)
• CMake >= 3.13.4
• Python 3.11–3.14
• Internet access (vcpkg downloads dependencies during build)

Build time: Approximately 5-15 minutes depending on your machine.

Performance Note

On Linux x86_64, the FourQlib elliptic curve assembly optimizations are disabled because the hand-optimized AVX2 assembly files use non-PIC relocations that are incompatible with Python shared extensions (.so files). The generic C fallback is used instead, which results in approximately 2-3x slower OPRF (Oblivious Pseudorandom Function) operations.

This does not affect the SEAL homomorphic encryption operations, which dominate runtime for typical set intersection sizes. On macOS and Windows, FourQlib uses different optimization paths that are not affected.

For maximum performance on Linux, consider building APSI as a standalone static library outside of Python and using the native CLI tools.

Example

Example usage of the labeled APSI server and client. The unlabeled variant can be used analogous to this.

from apsi import LabeledServer, LabeledClient

apsi_params = """
{
    "table_params": {
        "hash_func_count": 3,
        "table_size": 512,
        "max_items_per_bin": 92
    },
    "item_params": {"felts_per_item": 8},
    "query_params": {
        "ps_low_degree": 0,
        "query_powers": [1, 3, 4, 5, 8, 14, 20, 26, 32, 38, 41, 42, 43, 45, 46]
    },
    "seal_params": {
        "plain_modulus": 40961,
        "poly_modulus_degree": 4096,
        "coeff_modulus_bits": [40, 32, 32]
    }
}
"""

server = LabeledServer()
server.init_db(apsi_params, max_label_length=10)
server.add_items([("item", "1234567890"), ("abc", "123"), ("other", "my label")])

client = LabeledClient(apsi_params)

oprf_request = client.oprf_request(["item", "abc"])
oprf_response = server.handle_oprf_request(oprf_request)
query = client.build_query(oprf_response)
response = server.handle_query(query)
result = client.extract_result(response)

assert result == {"item": "1234567890", "abc": "123"}

To control multi threading and logging in APSI see apsi.utils.

Building & Testing

From Source

pip install -e .
pytest tests/

Building a Source Distribution

pip install build
python -m build --sdist