| 52 | |
| 53 | impl<G: AffineRepr> MAC<G> { |
| 54 | pub fn new<R: RngCore>( |
| 55 | rng: &mut R, |
| 56 | messages: &[G::ScalarField], |
| 57 | user_public_key: &UserPublicKey<G>, |
| 58 | signer_secret_key: &SecretKey<G::ScalarField>, |
| 59 | params: impl AsRef<MACParams<G>>, |
| 60 | ) -> Result<Self, KVACError> { |
| 61 | if messages.is_empty() { |
| 62 | return Err(KVACError::NoMessageGiven); |
| 63 | } |
| 64 | let params = params.as_ref(); |
| 65 | expect_equality!( |
| 66 | messages.len(), |
| 67 | params.supported_message_count(), |
| 68 | KVACError::MessageCountIncompatibleWithMACParams |
| 69 | ); |
| 70 | let mut e = G::ScalarField::rand(rng); |
| 71 | while (e + signer_secret_key.0).is_zero() { |
| 72 | e = G::ScalarField::rand(rng) |
| 73 | } |
| 74 | // 1/(e+x) |
| 75 | let e_plus_x_inv = (e + signer_secret_key.0).inverse().unwrap(); |
| 76 | let A = params.b(messages.iter().enumerate(), user_public_key)? * e_plus_x_inv; |
| 77 | Ok(Self { |
| 78 | A: A.into_affine(), |
| 79 | e, |
| 80 | }) |
| 81 | } |
| 82 | |
| 83 | pub fn verify( |
| 84 | &self, |