secure_inner_join.helper module

Module contains Helper class (Henri) for performing secure set intersection

class secure_inner_join.helper.Helper(*args, lsh_threshold_function=None, **kwargs)

Bases: Player

Class for a helper party

__init__(*args, lsh_threshold_function=None, **kwargs)

Initializes a helper instance

Parameters:

• *args (Any) – passed on to base class

• lsh_thresholds_function – threshold function for the LSH distance computation, if None defaults to Helper.default_threshold_function

• **kwargs (Any) – passed on to base class

Raises:

ValueError – raised when (at least) one of data parties is not in the pool.

async combine_and_send_to_all()

Computes the intersection size and sends the result to all data parties.

Raises:

ValueError – In case not all encrypted databases have been received (yet).

Return type:

None

static default_threshold_function(pairs, lookup_table)

Default threshold function implementation for validating whether two LSH hashes are near enough

Default is to allow the overall difference score to be <= 4.5 and the element-wise difference score to be <= 1.5 for all elements (day, month, year, zip2)

Parameters:

• pairs (list[tuple[tuple[int, int], tuple[int, int]]]) – pairs to compare

• lookup_table (dict[tuple[tuple[int, int], tuple[int, int]], tuple[float, tuple[float, float, float, float]]]) – lookup_table of scores for all pairs

Return type:

bool

Returns:

True if threshold function is satisfied, else False

property intersection_size: int

The size of the intersection between the identifier columns of all data parties.

Returns:

The intersection size.

Raises:

ValueError – In case the intersection size cannot be determined (yet).

lsh_distance(index_1, index_2)

Computes LSH distance between two indices. Every index is of the form (x, y) where x represents the party_index and y represents the index of the lsh hash.

Parameters:

• index_1 (tuple[int, int]) – of the form (party_index, lsh_hash_index)

• index_2 (tuple[int, int]) – of the form (party_index, lsh_hash_index)

Return type:

tuple[float, tuple[float, float, float, float]]

Returns:

overall and individual distance

async obtain_and_process_all_shares()

Receive the random shares from all data parties in an asynchronous manner and process them to determine the remainder of the shares from the data and the received shares.

Raises:

ValueError – In case the intersection has nog been computed yet.

Return type:

None

property paillier_schemes: list[Paillier]

Paillier schemes of all database owners.

Raises:

ValueError – Schemes have not yet been received.

Returns:

Paillier schemes of all database owners.

async receive_identifiers(party)

Receive hashed identifiers from party

Parameters:

party (str) – name of the party to receive data from

Return type:

None

async receive_lsh_identifiers(party)

Receive encoded Locality-Sensitive Hashing (LSH) identifiers from party

Parameters:

party (str) – name of the party to receive data from

Return type:

None

async receive_ph_identifiers(party)

Receive hashed phonetic identifiers from party

Parameters:

party (str) – name of the party to receive data from

Return type:

None

async run_protocol()

Run the entire protocol, start to end, in an asynchronous manner

Return type:

None

async send_data_parties()

Send the data parties with accompanying addresses and ports (that have been sorted alphabetically) to all players, so they can check that there data parties tuple is exactly the same.

Return type:

None

async send_shares_to_all()

Send the final encrypted shares to all parties.

Return type:

None

shutdown_received_schemes()

Shut down all Paillier schemes that were received.

Return type:

None

async store_data()

Receive and store the data from all data parties

Return type:

None

summed_lsh_distance(combination)

Computes the summed LSH distance of a set of pairs, returns “inf” if (at least) one of the distances exceeds a set threshold. As the number of pairs per combination is constant, it suffices to sum, no need to compute the mean.

Parameters:

combination (tuple[tuple[int, int], ...]) – a combination of an index pair per party.

Return type:

float

Returns:

sum of distances of all overall pair combinations or “inf”.