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fix(mint): verify KeyImage unique across inputs
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1. Mint reissue now verifies that KeyImage is unique across inputs.

2. Mint reissue now verifies that PublicKey is unique across outputs.

3. reverts KeyImage map changes from previous commit.

4. modifies tests to use unique keys per output/input
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@dan-da @dirvine
dan-da authored and dirvine committed Feb 17, 2022
1 parent 5d0b72f commit 56c62c8
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Showing 4 changed files with 135 additions and 96 deletions.
20 changes: 8 additions & 12 deletions src/builder.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -241,14 +241,14 @@ impl DbcBuilder {
let mut node_shares: Vec<NodeSignature> = rs
.mint_node_signatures
.iter()
.map(|e| e.1 .1 .1.clone())
.map(|e| e.1 .1.clone())
.collect();
mint_sig_shares.append(&mut node_shares);

let pub_key_sets: HashSet<PublicKeySet> = rs
.mint_node_signatures
.iter()
.map(|e| e.1 .1 .0.clone())
.map(|e| e.1 .0.clone())
.collect();

// add pubkeyset to HashSet, so we can verify there is only one distinct PubKeySet
Expand All @@ -260,11 +260,11 @@ impl DbcBuilder {
}

// Verify that each input has a NodeSignature
for (idx, mlsag) in rs.transaction.mlsags.iter().enumerate() {
for mlsag in rs.transaction.mlsags.iter() {
if !rs
.mint_node_signatures
.iter()
.any(|(i, (k, _))| *i == idx && *k == mlsag.key_image.to_compressed())
.keys()
.any(|k| *k == mlsag.key_image.to_compressed())
{
return Err(Error::ReissueShareMintNodeSignatureNotFoundForInput);
}
Expand Down Expand Up @@ -322,14 +322,10 @@ impl DbcBuilder {
transaction_sigs: transaction
.mlsags
.iter()
.enumerate()
.map(|(idx, mlsag)| {
.map(|mlsag| {
(
idx,
(
mlsag.key_image.to_compressed(),
(mint_public_key_set.public_key(), mint_sig.clone()),
),
mlsag.key_image.to_compressed(),
(mint_public_key_set.public_key(), mint_sig.clone()),
)
})
.collect(),
Expand Down
119 changes: 59 additions & 60 deletions src/dbc.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@ pub type KeyImage = [u8; 48]; // G1 compressed
pub struct Dbc {
pub content: DbcContent,
pub transaction: RingCtTransaction,
pub transaction_sigs: BTreeMap<usize, (KeyImage, (PublicKey, Signature))>,
pub transaction_sigs: BTreeMap<KeyImage, (PublicKey, Signature)>,
pub spent_proofs: BTreeSet<SpentProof>,
}

Expand All @@ -39,8 +39,7 @@ impl Dbc {
sha3.update(&self.content.hash().0);
sha3.update(&self.transaction.hash());

for (idx, (in_key, (mint_key, mint_sig))) in self.transaction_sigs.iter() {
sha3.update(&idx.to_le_bytes());
for (in_key, (mint_key, mint_sig)) in self.transaction_sigs.iter() {
sha3.update(in_key);
sha3.update(&mint_key.to_bytes());
sha3.update(&mint_sig.to_bytes());
Expand Down Expand Up @@ -118,7 +117,7 @@ mod tests {
dbc_owner: SecretKey,
dbc: Dbc,
n_ways: u8,
output_owner: PublicKey,
output_owners: Vec<PublicKey>,
spentbook_node: &MintNode<SimpleKeyManager>,
mut rng8: impl RngCore + rand_core::CryptoRng,
) -> Result<(ReissueRequest, Vec<RevealedCommitment>)> {
Expand All @@ -135,10 +134,14 @@ mod tests {
decoy_inputs,
&mut rng8,
)
.add_outputs(divide(amount, n_ways).map(|amount| Output {
amount,
public_key: BlsHelper::blsttc_to_blstrs_pubkey(&output_owner),
}))
.add_outputs(
divide(amount, n_ways)
.enumerate()
.map(|(idx, amount)| Output {
amount,
public_key: BlsHelper::blsttc_to_blstrs_pubkey(&output_owners[idx]),
}),
)
.build(&mut rng8)?;

let tx_hash = Hash::from(reissue_tx.hash());
Expand Down Expand Up @@ -222,6 +225,7 @@ mod tests {
let mut rng8 = rand8::rngs::StdRng::from_seed([0u8; 32]);
let mut rng = rand::rngs::StdRng::from_seed([0u8; 32]);

// let n_inputs = n_inputs.coerce::<u8>();
let amount = 100;
let mint_owner = crate::bls_dkg_id(&mut rng);

Expand All @@ -244,14 +248,10 @@ mod tests {
.transaction
.mlsags
.iter()
.enumerate()
.map(|(idx, mlsag)| {
.map(|mlsag| {
(
idx,
(
mlsag.key_image.to_compressed(),
(mint_owner.public_key_set.public_key(), genesis_sig.clone()),
),
mlsag.key_image.to_compressed(),
(mint_owner.public_key_set.public_key(), genesis_sig.clone()),
)
})
.collect(),
Expand All @@ -260,14 +260,23 @@ mod tests {
};

// let input_owner = crate::bls_dkg_id();
let input_owner = SecretKeySet::random(1, &mut rng);
let input_owner_blstrs = BlsHelper::blsttc_to_blstrs_sk(input_owner.secret_key());
let input_owners: Vec<SecretKeySet> = (0..=n_inputs.coerce())
.map(|_| SecretKeySet::random(1, &mut rng))
.collect();
let input_owners_blstrs: Vec<blstrs::Scalar> = input_owners
.iter()
.map(|sks| BlsHelper::blsttc_to_blstrs_sk(sks.secret_key()))
.collect();

let (reissue_request, revealed_commitments) = prepare_even_split(
BlsHelper::blstrs_to_blsttc_sk(genesis.secret_key),
genesis_dbc,
n_inputs.coerce(),
input_owner.public_keys().public_key(),
input_owners
.iter()
.map(|sks| sks.public_keys().public_key())
.collect(),
// input_owner.public_keys().public_key(),
&genesis_node,
&mut rng8,
)?;
Expand All @@ -282,12 +291,15 @@ mod tests {
let inputs: Vec<(blstrs::Scalar, AmountSecrets, Vec<blst_ringct::DecoyInput>)> =
output_dbcs
.into_iter()
.map(|dbc| {
let amount_secrets =
AmountSecrets::try_from((&input_owner, &dbc.content.amount_secrets_cipher))
.unwrap();
.enumerate()
.map(|(idx, dbc)| {
let amount_secrets = AmountSecrets::try_from((
&input_owners[idx],
&dbc.content.amount_secrets_cipher,
))
.unwrap();
let decoy_inputs = vec![]; // todo
(input_owner_blstrs, amount_secrets, decoy_inputs)
(input_owners_blstrs[idx], amount_secrets, decoy_inputs)
})
.collect();

Expand Down Expand Up @@ -330,51 +342,46 @@ mod tests {
let reissue_share = genesis_node.reissue(rr)?;
assert_eq!(reissue_tx.hash(), reissue_share.transaction.hash());

let (mint_key_set, mint_sig_share) = &reissue_share
.mint_node_signatures
.values()
.next()
.unwrap()
.1;
let (mint_key_set, mint_sig_share) =
&reissue_share.mint_node_signatures.values().next().unwrap();

let mint_sig = mint_key_set
.combine_signatures(vec![mint_sig_share.threshold_crypto()])
.unwrap();

let fuzzed_amt_secrets =
AmountSecrets::from_amount(amount + extra_output_amount.coerce::<Amount>(), &mut rng8);
let fuzzed_content =
DbcContent::from((input_owner.public_keys().public_key(), fuzzed_amt_secrets));
let fuzzed_content = DbcContent::from((
input_owners[0].public_keys().public_key(),
fuzzed_amt_secrets,
));

let mut fuzzed_transaction_sigs: BTreeMap<usize, (KeyImage, (PublicKey, Signature))> =
let mut fuzzed_transaction_sigs: BTreeMap<KeyImage, (PublicKey, Signature)> =
BTreeMap::new();

fuzzed_transaction_sigs.extend(
reissue_share
.mint_node_signatures
.iter()
.take(n_valid_sigs.coerce())
.map(|(idx, (in_owner, _))| {
.map(|(in_owner, _)| {
(
*idx,
(
*in_owner,
(genesis.public_key_set.public_key(), mint_sig.clone()),
),
*in_owner,
(genesis.public_key_set.public_key(), mint_sig.clone()),
)
}),
);

let mut repeating_inputs = reissue_tx
.mlsags
.iter()
.enumerate()
.cycle()
// skip the valid sigs so that we don't immediately overwrite them
.skip(n_valid_sigs.coerce());

// Invalid mint signatures BUT signing correct message
for _ in 0..n_wrong_signer_sigs.coerce() {
if let Some((idx, input)) = repeating_inputs.next() {
if let Some(input) = repeating_inputs.next() {
let id = crate::bls_dkg_id(&mut rng);
let key_manager = SimpleKeyManager::new(
SimpleSigner::from(id.clone()),
Expand All @@ -388,18 +395,15 @@ mod tests {
.combine_signatures(vec![trans_sig_share.threshold_crypto()])
.unwrap();
fuzzed_transaction_sigs.insert(
idx,
(
input.key_image.to_compressed(),
(id.public_key_set.public_key(), trans_sig),
),
input.key_image.to_compressed(),
(id.public_key_set.public_key(), trans_sig),
);
}
}

// Valid mint signatures BUT signing wrong message
for _ in 0..n_wrong_msg_sigs.coerce() {
if let Some((idx, input)) = repeating_inputs.next() {
if let Some(input) = repeating_inputs.next() {
let wrong_msg_sig = genesis_node.key_manager.sign(&Hash([0u8; 32])).unwrap();
let wrong_msg_mint_sig = genesis_node
.key_manager
Expand All @@ -409,23 +413,17 @@ mod tests {
.unwrap();

fuzzed_transaction_sigs.insert(
idx,
(
input.key_image.to_compressed(),
(genesis.public_key_set.public_key(), wrong_msg_mint_sig),
),
input.key_image.to_compressed(),
(genesis.public_key_set.public_key(), wrong_msg_mint_sig),
);
}
}

// Valid mint signatures for inputs not present in the transaction
for _ in 0..n_extra_input_sigs.coerce() {
fuzzed_transaction_sigs.insert(
rand::random::<usize>(),
(
[0u8; 48],
(genesis.public_key_set.public_key(), mint_sig.clone()),
),
[0u8; 48],
(genesis.public_key_set.public_key(), mint_sig.clone()),
);
}

Expand All @@ -442,7 +440,8 @@ mod tests {
let validation_res = dbc.confirm_valid(&key_manager);

let dbc_amount =
AmountSecrets::try_from((&input_owner, &dbc.content.amount_secrets_cipher))?.amount();
AmountSecrets::try_from((&input_owners[0], &dbc.content.amount_secrets_cipher))?
.amount();

match validation_res {
Ok(()) => {
Expand All @@ -467,7 +466,7 @@ mod tests {
Err(Error::UnknownInput) => {
assert!(n_extra_input_sigs.coerce::<u8>() > 0);
assert_ne!(
Vec::from_iter(dbc.transaction_sigs.values().map(|(k, _)| *k)),
Vec::from_iter(dbc.transaction_sigs.keys().copied()),
dbc.transaction
.mlsags
.iter()
Expand Down Expand Up @@ -496,14 +495,14 @@ mod tests {
assert!(dbc
.transaction_sigs
.values()
.any(|(_, (pk, _))| key_manager.verify_known_key(pk).is_err()));
.any(|(pk, _)| key_manager.verify_known_key(pk).is_err()));
}
Err(Error::Signing(s)) if s == Error::UnrecognisedAuthority.to_string() => {
assert!(n_wrong_signer_sigs.coerce::<u8>() > 0);
assert!(dbc
.transaction_sigs
.values()
.any(|(_, (pk, _))| key_manager.verify_known_key(pk).is_err()));
.any(|(pk, _)| key_manager.verify_known_key(pk).is_err()));
}
res => panic!("Unexpected verification result {:?}", res),
}
Expand Down
6 changes: 6 additions & 0 deletions src/error.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,12 @@ pub enum Error {
#[error("Dbc Content is not a member of transaction outputs")]
DbcContentNotPresentInTransactionOutput,

#[error("key image is not unique across all transaction inputs")]
KeyImageNotUniqueAcrossInputs,

#[error("public key is not unique across all transaction outputs")]
PublicKeyNotUniqueAcrossOutputs,

#[error("The number of SpentProof does not match the number of input MlsagSignature")]
SpentProofInputMismatch,

Expand Down
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