distributed_keygen.paillier_shared_key module

Paillier secret key that is shared amongst several parties.

class distributed_keygen.paillier_shared_key.PaillierSharedKey(n, t, player_id, share, theta)

Bases: SecretKey

Class containing relevant attributes and methods of a shared paillier key.

__init__(n, t, player_id, share, theta)

Initializes a Paillier shared key.

Parameters:

• n (int) – modulus of the DistributedPaillier scheme this secret key belongs to

• t (int) – corruption_threshold of the secret sharing

• player_id (int) – the index of the player to whom the key belongs

• share (IntegerShares) – secret sharing of the exponent used during decryption

• theta (int) – Value used in the computation of a full decryption after partial decryptions have been obtained. We refer to the paper for more details

__str__()

Utility function to represent the local share of the private key as a string.

Return type:

str

Returns:

String representation of this private key part.

decrypt(partial_dict)

Function that uses partial decryptions of other parties to reconstruct a full decryption of the initial ciphertext.

Parameters:

partial_dict (Dict[int, int]) – dictionary containing the partial decryptions of each party

Raises:

ValueError – Either in case not enough shares are known in order to decrypt. Or when the combined decryption minus one is not divisible by \(N\). This last case is most likely caused by the fact the ciphertext that is being decrypted, differs between parties.

Return type:

int

Returns:

full decryption

partial_decrypt(ciphertext)

Function that does local computations to get a partial decryption of a ciphertext.

Parameters:

ciphertext (PaillierCiphertext) – ciphertext to be partially decrypted

Raises:

• TypeError – If the given ciphertext is not of type PaillierCiphertext.

• ValueError – If the ciphertext is encrypted against a different key.

Return type:

int

Returns:

partial decryption of ciphertext