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Inverse dlog statement is built by the verifier, not by the prover #24

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Inverse dlog statement is built by the verifier, not by the prover #24

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17 changes: 6 additions & 11 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<usize>,
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 @@ -61,9 +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]
/// Generates the DlogStatement and CompositeProofs using the parameters generated by [generate_h1_h2_n_tilde]
fn generate_dlog_statement_proofs() -> (
DLogStatement,
DLogStatement,
CompositeDLogProof,
CompositeDLogProof,
Expand All @@ -87,7 +85,6 @@ 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 @@ -100,8 +97,7 @@ impl JoinMessage {
pub fn distribute() -> (Self, Keys) {
let pailier_key_pair = Keys::create(0);
let (
dlog_statement_base_h1,
dlog_statement_base_h2,
dlog_statement,
composite_dlog_proof_base_h1,
composite_dlog_proof_base_h2,
) = generate_dlog_statement_proofs();
Expand All @@ -110,8 +106,7 @@ impl JoinMessage {
// in a join message, we only care about the ek and the correctness proof
ek: pailier_key_pair.ek.clone(),
dk_correctness_proof: NICorrectKeyProof::proof(&pailier_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 @@ -207,11 +202,11 @@ impl JoinMessage {
let available_h1_h2_ntilde_vec: HashMap<usize, &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
12 changes: 9 additions & 3 deletions src/refresh_message.rs
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Expand Up @@ -212,7 +212,7 @@ impl<P> RefreshMessage<P> {
for join_message in new_parties.iter() {
let party_index = join_message.get_party_index()?;
key.paillier_key_vec[party_index - 1] = join_message.ek.clone();
key.h1_h2_n_tilde_vec[party_index - 1] = join_message.dlog_statement_base_h1.clone();
key.h1_h2_n_tilde_vec[party_index - 1] = join_message.dlog_statement.clone();
}

Ok(RefreshMessage::distribute(key))
Expand Down Expand Up @@ -281,13 +281,19 @@ impl<P> RefreshMessage<P> {
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