mithril_common/protocol/
multi_signer.rs

1use anyhow::{Context, anyhow};
2use mithril_stm::Parameters;
3
4use crate::{
5    StdResult,
6    crypto_helper::{
7        ProtocolAggregateVerificationKey, ProtocolAggregationError, ProtocolClerk,
8        ProtocolMultiSignature,
9    },
10    entities::SingleSignature,
11    protocol::ToMessage,
12};
13
14/// MultiSigner is the cryptographic engine in charge of producing multi-signatures from individual signatures
15pub struct MultiSigner {
16    protocol_clerk: ProtocolClerk,
17    protocol_parameters: Parameters,
18}
19
20impl MultiSigner {
21    pub(super) fn new(protocol_clerk: ProtocolClerk, protocol_parameters: Parameters) -> Self {
22        Self {
23            protocol_clerk,
24            protocol_parameters,
25        }
26    }
27
28    /// Aggregate the given single signatures into a multi-signature
29    pub fn aggregate_single_signatures<T: ToMessage>(
30        &self,
31        single_signatures: &[SingleSignature],
32        message: &T,
33    ) -> Result<ProtocolMultiSignature, ProtocolAggregationError> {
34        let protocol_signatures: Vec<_> = single_signatures
35            .iter()
36            .map(|single_signature| single_signature.to_protocol_signature())
37            .collect();
38
39        self.protocol_clerk
40            .aggregate_signatures(&protocol_signatures, message.to_message().as_bytes())
41            .map(|multi_sig| multi_sig.into())
42    }
43
44    /// Compute aggregate verification key from stake distribution
45    pub fn compute_aggregate_verification_key(&self) -> ProtocolAggregateVerificationKey {
46        self.protocol_clerk.compute_aggregate_verification_key().into()
47    }
48
49    /// Verify a single signature
50    pub fn verify_single_signature<T: ToMessage>(
51        &self,
52        message: &T,
53        single_signature: &SingleSignature,
54    ) -> StdResult<()> {
55        let protocol_signature = single_signature.to_protocol_signature();
56
57        let avk = self.compute_aggregate_verification_key();
58
59        // If there is no reg_party, then we simply received a signature from a non-registered
60        // party, and we can ignore the request.
61        let (vk, stake) = self
62            .protocol_clerk
63            .get_registered_party_for_index(&protocol_signature.signer_index)
64            .ok_or_else(|| {
65                anyhow!(format!(
66                    "Unregistered party: '{}'",
67                    single_signature.party_id
68                ))
69            })?;
70
71        protocol_signature
72            .verify(
73                &self.protocol_parameters,
74                &vk,
75                &stake,
76                &avk,
77                message.to_message().as_bytes(),
78            )
79            .with_context(|| {
80                format!(
81                    "Invalid signature for party: '{}'",
82                    single_signature.party_id
83                )
84            })?;
85
86        Ok(())
87    }
88}
89
90#[cfg(test)]
91mod test {
92    use mithril_stm::StmSignatureError;
93
94    use crate::{
95        entities::{ProtocolMessage, ProtocolMessagePartKey, ProtocolParameters},
96        protocol::SignerBuilder,
97        test::{
98            builder::{MithrilFixture, MithrilFixtureBuilder, StakeDistributionGenerationMethod},
99            double::fake_keys,
100        },
101    };
102
103    use super::*;
104
105    fn build_multi_signer(fixture: &MithrilFixture) -> MultiSigner {
106        SignerBuilder::new(
107            &fixture.signers_with_stake(),
108            &fixture.protocol_parameters(),
109        )
110        .unwrap()
111        .build_multi_signer()
112    }
113
114    #[test]
115    fn cant_aggregate_if_signatures_list_empty() {
116        let fixture = MithrilFixtureBuilder::default().with_signers(3).build();
117        let multi_signer = build_multi_signer(&fixture);
118        let message = ProtocolMessage::default();
119
120        let error = multi_signer.aggregate_single_signatures(&[], &message).expect_err(
121            "Multi-signature should not be created with an empty single signatures list",
122        );
123
124        assert!(
125            matches!(error, ProtocolAggregationError::NotEnoughSignatures(_, _)),
126            "Expected ProtocolAggregationError::NotEnoughSignatures, got: {error:?}"
127        )
128    }
129
130    #[test]
131    fn can_aggregate_if_valid_signatures_and_quorum_reached() {
132        let fixture = MithrilFixtureBuilder::default().with_signers(10).build();
133        let multi_signer = build_multi_signer(&fixture);
134        let message = ProtocolMessage::default();
135        let signatures: Vec<SingleSignature> = fixture
136            .signers_fixture()
137            .iter()
138            .map(|s| s.sign(&message).unwrap())
139            .collect();
140
141        multi_signer
142            .aggregate_single_signatures(&signatures, &message)
143            .expect("Multi-signature should be created");
144    }
145
146    #[test]
147    fn can_aggregate_even_with_one_invalid_signature_if_the_other_are_enough_for_the_quorum() {
148        let fixture = MithrilFixtureBuilder::default()
149            .with_signers(10)
150            .with_stake_distribution(StakeDistributionGenerationMethod::Uniform(20))
151            .with_protocol_parameters(ProtocolParameters::new(6, 200, 1.0))
152            .build();
153        let multi_signer = build_multi_signer(&fixture);
154        let message = ProtocolMessage::default();
155        let mut signatures: Vec<SingleSignature> = fixture
156            .signers_fixture()
157            .iter()
158            .map(|s| s.sign(&message).unwrap())
159            .collect();
160        signatures[4].signature = fake_keys::single_signature()[3].try_into().unwrap();
161
162        multi_signer
163            .aggregate_single_signatures(&signatures, &message)
164            .expect("Multi-signature should be created even with one invalid signature");
165    }
166
167    #[test]
168    fn verify_single_signature_fail_if_signature_signer_isnt_in_the_registered_parties() {
169        let multi_signer = build_multi_signer(
170            &MithrilFixtureBuilder::default()
171                .with_signers(1)
172                .with_stake_distribution(StakeDistributionGenerationMethod::RandomDistribution {
173                    seed: [3u8; 32],
174                    min_stake: 1,
175                })
176                .build(),
177        );
178        let fixture = MithrilFixtureBuilder::default().with_signers(1).build();
179        let message = ProtocolMessage::default();
180        let single_signature = fixture.signers_fixture().last().unwrap().sign(&message).unwrap();
181
182        // Will fail because the single signature was issued by a signer from a stake distribution
183        // that is not the one used by the multi-signer.
184        let error = multi_signer
185            .verify_single_signature(&message, &single_signature)
186            .expect_err(
187                "Verify single signature should fail if the signer isn't in the registered parties",
188            );
189
190        match error.downcast_ref::<StmSignatureError>() {
191            Some(StmSignatureError::SignatureInvalid(_)) => (),
192            _ => panic!("Expected an SignatureInvalid error, got: {error:?}"),
193        }
194    }
195
196    #[test]
197    fn verify_single_signature_fail_if_signature_signed_message_isnt_the_given_one() {
198        let fixture = MithrilFixtureBuilder::default().with_signers(1).build();
199        let multi_signer = build_multi_signer(&fixture);
200        let mut signed_message = ProtocolMessage::default();
201        signed_message.set_message_part(
202            ProtocolMessagePartKey::SnapshotDigest,
203            "a_digest".to_string(),
204        );
205        let single_signature = fixture
206            .signers_fixture()
207            .first()
208            .unwrap()
209            .sign(&signed_message)
210            .unwrap();
211
212        let error = multi_signer
213            .verify_single_signature(&ProtocolMessage::default(), &single_signature)
214            .expect_err("Verify single signature should fail");
215
216        match error.downcast_ref::<StmSignatureError>() {
217            Some(StmSignatureError::SignatureInvalid(_)) => (),
218            _ => panic!("Expected an SignatureInvalid error, got: {error:?}"),
219        }
220    }
221
222    #[test]
223    fn can_verify_valid_single_signature() {
224        let fixture = MithrilFixtureBuilder::default().with_signers(1).build();
225        let multi_signer = build_multi_signer(&fixture);
226        let message = ProtocolMessage::default();
227        let single_signature = fixture.signers_fixture().first().unwrap().sign(&message).unwrap();
228
229        multi_signer
230            .verify_single_signature(&message, &single_signature)
231            .expect("Verify single signature should succeed");
232    }
233}
mithril_common/protocol/multi_signer.rs

mithril_common/protocol/
multi_signer.rs
