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fix: inverse dlog statement is built by the verifier, and not by the prover #5

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merged 2 commits into from
Oct 19, 2022
Merged

fix: inverse dlog statement is built by the verifier, and not by the prover #5

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4ff55de
fix: inverse dlog statement is built by the verifier, and not by the …
DmytroTym Oct 28, 2021
bf6802a
Fmt and merge dmytro/dlog update
drewstone Oct 18, 2022
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28 changes: 8 additions & 20 deletions src/add_party_message.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -34,8 +34,7 @@ pub struct JoinMessage {
pub(crate) ek: EncryptionKey,
pub(crate) dk_correctness_proof: NiCorrectKeyProof,
pub(crate) party_index: Option<u16>,
pub(crate) dlog_statement_base_h1: DLogStatement,
pub(crate) dlog_statement_base_h2: DLogStatement,
pub(crate) dlog_statement: DLogStatement,
pub(crate) composite_dlog_proof_base_h1: CompositeDLogProof,
pub(crate) composite_dlog_proof_base_h2: CompositeDLogProof,
}
Expand All @@ -61,13 +60,8 @@ fn generate_h1_h2_n_tilde() -> (BigInt, BigInt, BigInt, BigInt, BigInt) {
(ek_tilde.n, h1, h2, xhi, xhi_inv)
}

/// Generates the DlogStatements and CompositeProofs using the parameters generated by [generate_h1_h2_n_tilde]
fn generate_dlog_statement_proofs() -> (
DLogStatement,
DLogStatement,
CompositeDLogProof,
CompositeDLogProof,
) {
/// Generates the DlogStatement and CompositeProofs using the parameters generated by [generate_h1_h2_n_tilde]
fn generate_dlog_statement_proofs() -> (DLogStatement, CompositeDLogProof, CompositeDLogProof) {
let (n_tilde, h1, h2, xhi, xhi_inv) = generate_h1_h2_n_tilde();

let dlog_statement_base_h1 = DLogStatement {
Expand All @@ -87,7 +81,6 @@ fn generate_dlog_statement_proofs() -> (

(
dlog_statement_base_h1,
dlog_statement_base_h2,
composite_dlog_proof_base_h1,
composite_dlog_proof_base_h2,
)
Expand All @@ -102,19 +95,14 @@ impl JoinMessage {
/// [Keys] that are going to be used when generating the [LocalKey].
pub fn distribute() -> (Self, Keys) {
let paillier_key_pair = Keys::create(0);
let (
dlog_statement_base_h1,
dlog_statement_base_h2,
composite_dlog_proof_base_h1,
composite_dlog_proof_base_h2,
) = generate_dlog_statement_proofs();
let (dlog_statement, composite_dlog_proof_base_h1, composite_dlog_proof_base_h2) =
generate_dlog_statement_proofs();

let join_message = JoinMessage {
// in a join message, we only care about the ek and the correctness proof
ek: paillier_key_pair.ek.clone(),
dk_correctness_proof: NiCorrectKeyProof::proof(&paillier_key_pair.dk, None),
dlog_statement_base_h1,
dlog_statement_base_h2,
dlog_statement,
composite_dlog_proof_base_h1,
composite_dlog_proof_base_h2,
party_index: None,
Expand Down Expand Up @@ -211,11 +199,11 @@ impl JoinMessage {
let available_h1_h2_ntilde_vec: HashMap<u16, &DLogStatement> = refresh_messages
.iter()
.map(|msg| (msg.party_index, &msg.dlog_statement))
.chain(std::iter::once((party_index, &self.dlog_statement_base_h1)))
.chain(std::iter::once((party_index, &self.dlog_statement)))
.chain(join_messages.iter().map(|join_message| {
(
join_message.party_index.unwrap(),
&join_message.dlog_statement_base_h1,
&join_message.dlog_statement,
)
}))
.collect();
Expand Down
14 changes: 10 additions & 4 deletions src/refresh_message.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -236,14 +236,14 @@ impl<E: Curve, H: Digest + Clone> RefreshMessage<E, H> {
key.h1_h2_n_tilde_vec.remove((party_index - 1) as usize);
key.h1_h2_n_tilde_vec.insert(
(party_index - 1) as usize,
join_message.dlog_statement_base_h1.clone(),
join_message.dlog_statement.clone(),
);
} else {
key.paillier_key_vec
.insert((party_index - 1) as usize, join_message.ek.clone());
key.h1_h2_n_tilde_vec.insert(
(party_index - 1) as usize,
join_message.dlog_statement_base_h1.clone(),
join_message.dlog_statement.clone(),
);
}
}
Expand Down Expand Up @@ -324,13 +324,19 @@ impl<E: Curve, H: Digest + Clone> RefreshMessage<E, H> {
return Err(FsDkrError::PaillierVerificationError { party_index });
}

// creating an inverse dlog statement
let dlog_statement_base_h2 = DLogStatement {
N: join_message.dlog_statement.N.clone(),
g: join_message.dlog_statement.ni.clone(),
ni: join_message.dlog_statement.g.clone(),
};
if join_message
.composite_dlog_proof_base_h1
.verify(&join_message.dlog_statement_base_h1)
.verify(&join_message.dlog_statement)
.is_err()
|| join_message
.composite_dlog_proof_base_h2
.verify(&join_message.dlog_statement_base_h2)
.verify(&dlog_statement_base_h2)
.is_err()
{
return Err(FsDkrError::DLogProofValidation { party_index });
Expand Down