# TNO PET Lab - secure Multi-Party Computation (MPC) - Protocols - Secure Comparison
Implementation of a secure comparison protocol based on the DGK encryption
scheme. The implementation follows the description of the paper
[Improving the DGK comparison
protocol](https://doi.org/10.1109/WIFS.2012.6412624), a paper by Thijs Veugen
improving upon the secure comparison protocol by [Damgård, Geisler, and
Krøigaard](https://doi.org/10.1007/978-3-540-73458-1_30).
Note that a correction was published in [Correction to "Improving the DGK
comparison protocol"](https://doi.org/10.1109/WIFS.2012.6412624), which is
incorporated in the implementation.
### PET Lab
The TNO PET Lab consists of generic software components, procedures, and functionalities developed and maintained on a regular basis to facilitate and aid in the development of PET solutions. The lab is a cross-project initiative allowing us to integrate and reuse previously developed PET functionalities to boost the development of new protocols and solutions.
The package `tno.mpc.protocols.secure_comparison` is part of the [TNO Python Toolbox](https://github.com/TNO-PET).
_Limitations in (end-)use: the content of this software package may solely be used for applications that comply with international export control laws._
_This implementation of cryptographic software has not been audited. Use at your own risk._
## Documentation
Documentation of the `tno.mpc.protocols.secure_comparison` package can be found
[here](https://docs.pet.tno.nl/mpc/protocols/secure_comparison/4.4.0).
## Install
Easily install the `tno.mpc.protocols.secure_comparison` package using `pip`:
```console
$ python -m pip install tno.mpc.protocols.secure_comparison
```
_Note:_ If you are cloning the repository and wish to edit the source code, be
sure to install the package in editable mode:
```console
$ python -m pip install -e 'tno.mpc.protocols.secure_comparison'
```
If you wish to run the tests you can use:
```console
$ python -m pip install 'tno.mpc.protocols.secure_comparison[tests]'
```
_Note:_ A significant performance improvement can be achieved by installing the GMPY2 library.
```console
$ python -m pip install 'tno.mpc.protocols.secure_comparison[gmpy]'
```
## Usage
Usage example:
```python
import asyncio
from tno.mpc.communication import Pool
from tno.mpc.encryption_schemes.dgk import DGK
from tno.mpc.encryption_schemes.paillier import Paillier
from tno.mpc.encryption_schemes.utils import next_prime
from tno.mpc.protocols.secure_comparison import Initiator, KeyHolder
async def run_protocol() -> None:
taskA = asyncio.create_task(alice.perform_secure_comparison(x_enc, y_enc))
taskB = asyncio.create_task(bob.perform_secure_comparison())
x_leq_y_enc, _ = await asyncio.gather(*[taskA, taskB])
x_leq_y = scheme_paillier.decrypt(x_leq_y_enc)
assert x_leq_y == 1
if __name__ == "__main__":
# Set maximum bit length
l = 16
# Setup the Paillier scheme
scheme_paillier = Paillier.from_security_parameter(key_length=2048)
# Setup the DGK scheme. This may take up to a minute.
u = next_prime((1 << (l + 2)))
scheme_dgk = DGK.from_security_parameter(
v_bits=160, n_bits=2048, u=u, full_decryption=False
)
# Setup communication pools
pool_alice = Pool()
pool_alice.add_http_server(8040)
pool_alice.add_http_client("keyholder", "localhost", 8041)
pool_bob = Pool()
pool_bob.add_http_server(8041)
pool_bob.add_http_client("initiator", "localhost", 8040)
# Encrypt two numbers (x,y) for the protocol and set the maximum bit_length (l)
x = 23
y = 42
x_enc = scheme_paillier.unsafe_encrypt(x)
y_enc = scheme_paillier.unsafe_encrypt(y)
alice = Initiator(l, communicator=pool_alice, other_party="keyholder")
bob = KeyHolder(
l,
communicator=pool_bob,
other_party="initiator",
scheme_paillier=scheme_paillier,
scheme_dgk=scheme_dgk,
)
# Run entire protocol interactively:
loop = asyncio.get_event_loop()
loop.run_until_complete(run_protocol())
# Or execute the protocol steps without interaction
z_enc, r = alice.step_1(x_enc, y_enc, l, scheme_paillier)
z, beta = bob.step_2(z_enc, l, scheme_paillier)
alpha = alice.step_3(r, l)
d_enc = bob.step_4a(z, scheme_dgk, scheme_paillier, l)
beta_is_enc = bob.step_4b(beta, l, scheme_dgk)
d_enc = alice.step_4c(d_enc, r, scheme_dgk, scheme_paillier)
alpha_is_xor_beta_is_enc = alice.step_4d(alpha, beta_is_enc)
w_is_enc, alpha_tilde = alice.step_4e(
r, alpha, alpha_is_xor_beta_is_enc, d_enc, scheme_paillier
)
w_is_enc = alice.step_4f(w_is_enc)
s, delta_a = alice.step_4g()
c_is_enc = alice.step_4h(
s, alpha, alpha_tilde, d_enc, beta_is_enc, w_is_enc, delta_a, scheme_dgk
)
c_is_enc = alice.step_4i(c_is_enc, scheme_dgk)
delta_b = bob.step_4j(c_is_enc, scheme_dgk)
zeta_1_enc, zeta_2_enc, delta_b_enc = bob.step_5(z, l, delta_b, scheme_paillier)
beta_lt_alpha_enc = alice.step_6(delta_a, delta_b_enc)
x_leq_y_enc = alice.step_7(
zeta_1_enc, zeta_2_enc, r, l, beta_lt_alpha_enc, scheme_paillier
)
x_leq_y = scheme_paillier.decrypt(x_leq_y_enc)
assert x_leq_y == 1
# Shut down encryption schemes (optional but recommended)
alice.scheme_paillier.shut_down()
alice.scheme_dgk.shut_down()
bob.scheme_paillier.shut_down()
bob.scheme_dgk.shut_down()
```
The communicator object is required only when the protocol is ran through `perform_secure_comparison`. In that case, one may choose to pass any communicator object that adheres to the `tno.mpc.protocols.secure_comparison.Communicator` protocol. An example can be found in the unit tests.
### ! SAFETY NOTICE ! ENSURE CIPHERTEXTS ARE RANDOMIZED
Since version 2.0.0 of `tno.mpc.encryption_schemes.paillier` and `tno.mpc.encryption_schemes.dgk`, it is possible to (potentially) make protocols more efficient by delaying randomization of ciphertexts. This library always operates in this 'expert' mode and therefore several protocol steps yield non-randomized ciphertext outputs. As a consequence, if the user chooses to perform the secure comparison steps manually, she needs to make sure that the resulting ciphertexts are randomized before they are communicated. If the `tno.mpc.communication` library is used (or more specifically, the Paillier and DGK serialize methods), then this will be done automatically for you (but warnings might be raised).
Raw data
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"description": "# TNO PET Lab - secure Multi-Party Computation (MPC) - Protocols - Secure Comparison\n\nImplementation of a secure comparison protocol based on the DGK encryption\nscheme. The implementation follows the description of the paper\n[Improving the DGK comparison\nprotocol](https://doi.org/10.1109/WIFS.2012.6412624), a paper by Thijs Veugen\nimproving upon the secure comparison protocol by [Damg\u00e5rd, Geisler, and\nKr\u00f8igaard](https://doi.org/10.1007/978-3-540-73458-1_30).\n\nNote that a correction was published in [Correction to \"Improving the DGK\ncomparison protocol\"](https://doi.org/10.1109/WIFS.2012.6412624), which is\nincorporated in the implementation.\n\n### PET Lab\n\nThe TNO PET Lab consists of generic software components, procedures, and functionalities developed and maintained on a regular basis to facilitate and aid in the development of PET solutions. The lab is a cross-project initiative allowing us to integrate and reuse previously developed PET functionalities to boost the development of new protocols and solutions.\n\nThe package `tno.mpc.protocols.secure_comparison` is part of the [TNO Python Toolbox](https://github.com/TNO-PET).\n\n_Limitations in (end-)use: the content of this software package may solely be used for applications that comply with international export control laws._ \n_This implementation of cryptographic software has not been audited. Use at your own risk._\n\n## Documentation\n\nDocumentation of the `tno.mpc.protocols.secure_comparison` package can be found\n[here](https://docs.pet.tno.nl/mpc/protocols/secure_comparison/4.4.0).\n\n## Install\n\nEasily install the `tno.mpc.protocols.secure_comparison` package using `pip`:\n\n```console\n$ python -m pip install tno.mpc.protocols.secure_comparison\n```\n\n_Note:_ If you are cloning the repository and wish to edit the source code, be\nsure to install the package in editable mode:\n\n```console\n$ python -m pip install -e 'tno.mpc.protocols.secure_comparison'\n```\n\nIf you wish to run the tests you can use:\n\n```console\n$ python -m pip install 'tno.mpc.protocols.secure_comparison[tests]'\n```\n\n_Note:_ A significant performance improvement can be achieved by installing the GMPY2 library.\n\n```console\n$ python -m pip install 'tno.mpc.protocols.secure_comparison[gmpy]'\n```\n\n## Usage\n\nUsage example:\n\n```python\nimport asyncio\n\nfrom tno.mpc.communication import Pool\nfrom tno.mpc.encryption_schemes.dgk import DGK\nfrom tno.mpc.encryption_schemes.paillier import Paillier\nfrom tno.mpc.encryption_schemes.utils import next_prime\n\nfrom tno.mpc.protocols.secure_comparison import Initiator, KeyHolder\n\n\nasync def run_protocol() -> None:\n taskA = asyncio.create_task(alice.perform_secure_comparison(x_enc, y_enc))\n taskB = asyncio.create_task(bob.perform_secure_comparison())\n\n x_leq_y_enc, _ = await asyncio.gather(*[taskA, taskB])\n x_leq_y = scheme_paillier.decrypt(x_leq_y_enc)\n assert x_leq_y == 1\n\n\nif __name__ == \"__main__\":\n # Set maximum bit length\n l = 16\n # Setup the Paillier scheme\n scheme_paillier = Paillier.from_security_parameter(key_length=2048)\n # Setup the DGK scheme. This may take up to a minute.\n u = next_prime((1 << (l + 2)))\n scheme_dgk = DGK.from_security_parameter(\n v_bits=160, n_bits=2048, u=u, full_decryption=False\n )\n\n # Setup communication pools\n pool_alice = Pool()\n pool_alice.add_http_server(8040)\n pool_alice.add_http_client(\"keyholder\", \"localhost\", 8041)\n pool_bob = Pool()\n pool_bob.add_http_server(8041)\n pool_bob.add_http_client(\"initiator\", \"localhost\", 8040)\n\n # Encrypt two numbers (x,y) for the protocol and set the maximum bit_length (l)\n x = 23\n y = 42\n x_enc = scheme_paillier.unsafe_encrypt(x)\n y_enc = scheme_paillier.unsafe_encrypt(y)\n\n alice = Initiator(l, communicator=pool_alice, other_party=\"keyholder\")\n bob = KeyHolder(\n l,\n communicator=pool_bob,\n other_party=\"initiator\",\n scheme_paillier=scheme_paillier,\n scheme_dgk=scheme_dgk,\n )\n\n # Run entire protocol interactively:\n loop = asyncio.get_event_loop()\n loop.run_until_complete(run_protocol())\n\n # Or execute the protocol steps without interaction\n z_enc, r = alice.step_1(x_enc, y_enc, l, scheme_paillier)\n z, beta = bob.step_2(z_enc, l, scheme_paillier)\n alpha = alice.step_3(r, l)\n d_enc = bob.step_4a(z, scheme_dgk, scheme_paillier, l)\n beta_is_enc = bob.step_4b(beta, l, scheme_dgk)\n d_enc = alice.step_4c(d_enc, r, scheme_dgk, scheme_paillier)\n alpha_is_xor_beta_is_enc = alice.step_4d(alpha, beta_is_enc)\n w_is_enc, alpha_tilde = alice.step_4e(\n r, alpha, alpha_is_xor_beta_is_enc, d_enc, scheme_paillier\n )\n w_is_enc = alice.step_4f(w_is_enc)\n s, delta_a = alice.step_4g()\n c_is_enc = alice.step_4h(\n s, alpha, alpha_tilde, d_enc, beta_is_enc, w_is_enc, delta_a, scheme_dgk\n )\n c_is_enc = alice.step_4i(c_is_enc, scheme_dgk)\n delta_b = bob.step_4j(c_is_enc, scheme_dgk)\n zeta_1_enc, zeta_2_enc, delta_b_enc = bob.step_5(z, l, delta_b, scheme_paillier)\n beta_lt_alpha_enc = alice.step_6(delta_a, delta_b_enc)\n x_leq_y_enc = alice.step_7(\n zeta_1_enc, zeta_2_enc, r, l, beta_lt_alpha_enc, scheme_paillier\n )\n x_leq_y = scheme_paillier.decrypt(x_leq_y_enc)\n assert x_leq_y == 1\n\n # Shut down encryption schemes (optional but recommended)\n alice.scheme_paillier.shut_down()\n alice.scheme_dgk.shut_down()\n bob.scheme_paillier.shut_down()\n bob.scheme_dgk.shut_down()\n```\n\nThe communicator object is required only when the protocol is ran through `perform_secure_comparison`. 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