Linear Scan

The linear scan example scans a list of secret values from multiple parties, checking for the existence of specific values. The example uses a reusable helper function for the logic for determining whether a given value is present or isn't present in the list.

Nada program

src/list_scan_linear.py

from nada_dsl import *
import nada_numpy as na

def is_number_present_in_list(array: List[SecretInteger], value: Integer) -> SecretBoolean:
    result = Integer(0)
    for element in array:
        # If the element is equal to the value, add 1 to the result.
        result += (value == element).if_else(Integer(1), Integer(0))
    return (result > Integer(0))

def nada_main():
    num_parties = 10
    parties = na.parties(num_parties)

    secrets_list = []
    for i in range(num_parties):
        secrets_list.append(
            SecretInteger(Input(name="num_" + str(i), party=parties[i]))
        )

    # Check if 100 is a secret value in the list
    is_present_1 = is_number_present_in_list(secrets_list, Integer(100))

    # Check if 99 is a secret value in the list
    is_present_2 = is_number_present_in_list(secrets_list, Integer(99))

    return [
        Output(is_present_1, "is_present_1", party=parties[0]),
        Output(is_present_2, "is_present_2", party=parties[0]),
    ]

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Test file

tests/list_scan_linear_test.yaml

---
program: list_scan_linear
inputs:
  num_0: 10
  num_2: 20
  num_1: 30
  num_4: 40
  num_9: 50
  num_6: 60
  num_7: 70
  num_8: 80
  num_5: 90
  num_3: 100
expected_outputs:
  is_present_1: true
  is_present_2: false

View on GitHub

Run and test the list_scan_linear program

1. Open "Nada by Example"

2. Run the program with inputs from the test file

nada run list_scan_linear_test

3. Test the program with inputs from the test file against the expected_outputs from the test file

nada test list_scan_linear_test