Player

class threshold_elgamal.player.Player(i, params)

Player that takes part in a threshold ElGamal cryptosystem.

Parameters

• i (int) – Player identifier.

• params (dict) – Parameters of the threshold scheme: primes p and q, generators g and h, total number of players n and threshold k.

check_pk_commits(commits, failed_shares)

Checks commits for the construction of the public key. If any of the commits fail, the received share of that player is returned and used later when constructing the public key without said player’s involvement.

Parameters

• commits (dict) – Commitments.

• failed_shares (dict) – Dictionary of received shares of players for whom the check failed. Used later while constructing the public key.

check_shares(commits, players)

Checks commitments for the shares and complains if the check fails.

Parameters

• commits (dict) – Commitments.

• players (list) – List of players.

commit()

Creates commitments for coefficients of the generated random polynomials.

Returns

Commitments.

Rtype list

commit_pk()

Generates commitments for the construction of the public key.

Returns

Commitments.

Return type

list

complain(player)

Processes complains to player. If the player received more than t = k-1 complaints, they are disqualified.

Parameters

player (Player) – Player who receives the complaint.

construct_decryption_share(c1)

Constructs decryption share used later in decryption of the message.

Parameters

c1 (gmpy2.mpz) – Encryption part c1.

construct_pk(commits)

Constructs public key from public key commitments.

Parameters

commits (dict) – Commitments.

get_decryption_share(c1)

Fetches the decryption share.

Parameters

c1 (gmpy2.mpz) – Encryption part c1.

Returns

Decryption share.

Return type

gmpy2.mpz

get_pk()

Fetches the public key.

Returns

Public key.

Return type

gmpy2.mpz

send_shares(players)

Sends a pair of shares to each of the players.

Parameters

players (list) – List of players (including self).