Small fixes

synedrion/src/paillier/encryption.rs

@@ -140,23 +140,7 @@ impl<P: PaillierParams> Ciphertext<P> {
         randomizer: &MaskedRandomizer<P>,
         plaintext_is_negative: Choice,
     ) -> Self {
-        // Technically if `abs_plaintext` is greater than the modulus of `pk`,
-        // it will be effectively reduced modulo `pk`.
-        // But some ZK proofs with `TestParams` may still supply a value larger than `pk`
-        // because they are not planning on decrypting the resulting ciphertext;
-        // they just construct an encryption of the same value in two different ways
-        // and then compare the results.
-        // (And the value can be larger than `pk` because of some restrictions on
-        // `SchemeParameters`/`PaillierParameters` values in tests, which can only
-        // be overcome by fixing #27 and using a small 32- or 64-bit curve for tests)
-
-        // Calculate the ciphertext `C = (N + 1)^m * rho^N mod N^2`
-        // where `N` is the Paillier composite modulus, `m` is the plaintext,
-        // and `rho` is the randomizer.
-
-        // Simplify `(N + 1)^m mod N^2 == 1 + m * N mod N^2`.
-        // Since `m` can be negative, we calculate `m * N +- 1` (never overflows since `m < N`),
-        // then conditionally negate modulo N^2
+        // Same as `new_with_randomizer_inner`, but works on public data.
 
         let prod = abs_plaintext.mul_wide(pk.modulus());
         let mut prod_mod = prod.to_montgomery(pk.monty_params_mod_n_squared());
@@ -282,8 +266,11 @@ impl<P: PaillierParams> Ciphertext<P> {
         assert_eq!(sk.public_key(), &self.pk);
 
         let pk = sk.public_key();
-        let positive_result = self.decrypt(sk); // Note that this is in range `[0, N)`
-                                                // Can't define a `Sub<Secret>` for `Uint`, so have to re-wrap manually.
+
+        // Note that this is in range `[0, N)`
+        let positive_result = self.decrypt(sk);
+
+        // Can't define a `Sub<Secret>` for `Uint`, so have to re-wrap manually.
         let negative_result = Secret::init_with(|| *pk.modulus() - positive_result.expose_secret());
         let is_negative = positive_result
             .expose_secret()

synedrion/src/tools/secret.rs

@@ -142,7 +142,7 @@ where
     }
 
     pub fn to_signed(&self) -> Option<Secret<Signed<T>>> {
-        Secret::try_init_with(|| self.expose_secret().clone().into_signed().ok_or(|| ())).ok()
+        Secret::maybe_init_with(|| self.expose_secret().clone().into_signed())
     }
 }