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