Separate keys and key shares.
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368430be1c
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a78a14fa9d
126
mod.rs
126
mod.rs
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@ -28,7 +28,7 @@ const CHACHA_RNG_SEED_SIZE: usize = 8;
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const ERR_OS_RNG: &str = "could not initialize the OS random number generator";
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const ERR_OS_RNG: &str = "could not initialize the OS random number generator";
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/// A public key, or a public key share.
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/// A public key.
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#[derive(Deserialize, Serialize, Copy, Clone, PartialEq, Eq)]
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#[derive(Deserialize, Serialize, Copy, Clone, PartialEq, Eq)]
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pub struct PublicKey(#[serde(with = "serde_impl::projective")] G1);
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pub struct PublicKey(#[serde(with = "serde_impl::projective")] G1);
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@ -57,13 +57,6 @@ impl PublicKey {
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self.verify_g2(sig, hash_g2(msg))
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self.verify_g2(sig, hash_g2(msg))
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}
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}
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/// Returns `true` if the decryption share matches the ciphertext.
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pub fn verify_decryption_share(&self, share: &DecryptionShare, ct: &Ciphertext) -> bool {
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let Ciphertext(ref u, ref v, ref w) = *ct;
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let hash = hash_g1_g2(*u, v);
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Bls12::pairing(share.0, hash) == Bls12::pairing(self.0, *w)
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}
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/// Encrypts the message.
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/// Encrypts the message.
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pub fn encrypt<M: AsRef<[u8]>>(&self, msg: M) -> Ciphertext {
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pub fn encrypt<M: AsRef<[u8]>>(&self, msg: M) -> Ciphertext {
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let r: Fr = OsRng::new().expect(ERR_OS_RNG).gen();
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let r: Fr = OsRng::new().expect(ERR_OS_RNG).gen();
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@ -82,8 +75,44 @@ impl PublicKey {
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}
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}
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}
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}
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/// A signature, or a signature share.
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/// A public key share.
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// note: random signatures can be generated for testing
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#[derive(Deserialize, Serialize, Clone, PartialEq, Eq, Hash)]
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pub struct PublicKeyShare(PublicKey);
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impl fmt::Debug for PublicKeyShare {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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let uncomp = (self.0).0.into_affine().into_uncompressed();
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let bytes = uncomp.as_ref();
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write!(f, "PublicKeyShare({:?})", HexBytes(bytes))
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}
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}
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impl PublicKeyShare {
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/// Returns `true` if the signature matches the element of `G2`.
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pub fn verify_g2<H: Into<G2Affine>>(&self, sig: &SignatureShare, hash: H) -> bool {
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self.0.verify_g2(&sig.0, hash)
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}
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/// Returns `true` if the signature matches the message.
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pub fn verify<M: AsRef<[u8]>>(&self, sig: &SignatureShare, msg: M) -> bool {
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self.verify_g2(sig, hash_g2(msg))
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}
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/// Returns `true` if the decryption share matches the ciphertext.
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pub fn verify_decryption_share(&self, share: &DecryptionShare, ct: &Ciphertext) -> bool {
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let Ciphertext(ref u, ref v, ref w) = *ct;
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let hash = hash_g1_g2(*u, v);
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Bls12::pairing(share.0, hash) == Bls12::pairing((self.0).0, *w)
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}
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/// Returns a byte string representation of the public key share.
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pub fn to_bytes(&self) -> Vec<u8> {
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self.0.to_bytes()
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}
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}
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/// A signature.
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// Note: Random signatures can be generated for testing.
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#[derive(Deserialize, Serialize, Clone, PartialEq, Eq, Rand)]
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#[derive(Deserialize, Serialize, Clone, PartialEq, Eq, Rand)]
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pub struct Signature(#[serde(with = "serde_impl::projective")] G2);
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pub struct Signature(#[serde(with = "serde_impl::projective")] G2);
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@ -112,7 +141,20 @@ impl Signature {
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}
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}
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}
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}
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/// A secret key, or a secret key share.
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/// A signature share.
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// Note: Random signature shares can be generated for testing.
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#[derive(Deserialize, Serialize, Clone, PartialEq, Eq, Rand, Hash)]
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pub struct SignatureShare(pub(crate) Signature);
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impl fmt::Debug for SignatureShare {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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let uncomp = (self.0).0.into_affine().into_uncompressed();
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let bytes = uncomp.as_ref();
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write!(f, "SignatureShare({:?})", HexBytes(bytes))
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}
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}
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/// A secret key.
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#[derive(Clone, PartialEq, Eq, Rand)]
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#[derive(Clone, PartialEq, Eq, Rand)]
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pub struct SecretKey(Fr);
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pub struct SecretKey(Fr);
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@ -169,13 +211,47 @@ impl SecretKey {
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let g = u.into_affine().mul(self.0);
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let g = u.into_affine().mul(self.0);
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Some(xor_vec(&hash_bytes(g, v.len()), v))
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Some(xor_vec(&hash_bytes(g, v.len()), v))
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}
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}
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}
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/// A secret key share.
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#[derive(Clone, PartialEq, Eq, Rand, Default)]
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pub struct SecretKeyShare(SecretKey);
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impl fmt::Debug for SecretKeyShare {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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let uncomp = self.0.public_key().0.into_affine().into_uncompressed();
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let bytes = uncomp.as_ref();
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write!(f, "SecretKeyShare({:?})", HexBytes(bytes))
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}
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}
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impl SecretKeyShare {
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/// Creates a secret key share from an existing value
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pub fn from_value(f: Fr) -> Self {
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SecretKeyShare(SecretKey::from_value(f))
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}
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/// Returns the matching public key share.
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pub fn public_key_share(&self) -> PublicKeyShare {
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PublicKeyShare(self.0.public_key())
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}
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/// Signs the given element of `G2`.
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pub fn sign_g2<H: Into<G2Affine>>(&self, hash: H) -> SignatureShare {
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SignatureShare(self.0.sign_g2(hash))
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}
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/// Signs the given message.
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pub fn sign<M: AsRef<[u8]>>(&self, msg: M) -> SignatureShare {
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SignatureShare(self.0.sign(msg))
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}
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/// Returns a decryption share, or `None`, if the ciphertext isn't valid.
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/// Returns a decryption share, or `None`, if the ciphertext isn't valid.
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pub fn decrypt_share(&self, ct: &Ciphertext) -> Option<DecryptionShare> {
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pub fn decrypt_share(&self, ct: &Ciphertext) -> Option<DecryptionShare> {
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if !ct.verify() {
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if !ct.verify() {
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return None;
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return None;
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}
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}
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Some(DecryptionShare(ct.0.into_affine().mul(self.0)))
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Some(DecryptionShare(ct.0.into_affine().mul((self.0).0)))
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}
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}
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}
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}
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@ -249,17 +325,18 @@ impl PublicKeySet {
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}
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}
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/// Returns the `i`-th public key share.
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/// Returns the `i`-th public key share.
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pub fn public_key_share<T: Into<FrRepr>>(&self, i: T) -> PublicKey {
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pub fn public_key_share<T: Into<FrRepr>>(&self, i: T) -> PublicKeyShare {
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PublicKey(self.commit.evaluate(from_repr_plus_1::<Fr>(i.into())))
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let value = self.commit.evaluate(from_repr_plus_1::<Fr>(i.into()));
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PublicKeyShare(PublicKey(value))
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}
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}
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/// Combines the shares into a signature that can be verified with the main public key.
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/// Combines the shares into a signature that can be verified with the main public key.
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pub fn combine_signatures<'a, ITR, IND>(&self, shares: ITR) -> Result<Signature>
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pub fn combine_signatures<'a, ITR, IND>(&self, shares: ITR) -> Result<Signature>
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where
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where
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ITR: IntoIterator<Item = (&'a IND, &'a Signature)>,
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ITR: IntoIterator<Item = (&'a IND, &'a SignatureShare)>,
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IND: Into<FrRepr> + Clone + 'a,
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IND: Into<FrRepr> + Clone + 'a,
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{
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{
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let samples = shares.into_iter().map(|(i, share)| (i, &share.0));
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let samples = shares.into_iter().map(|(i, share)| (i, &(share.0).0));
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Ok(Signature(interpolate(self.commit.degree() + 1, samples)?))
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Ok(Signature(interpolate(self.commit.degree() + 1, samples)?))
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}
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}
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@ -304,8 +381,9 @@ impl SecretKeySet {
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}
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}
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/// Returns the `i`-th secret key share.
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/// Returns the `i`-th secret key share.
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pub fn secret_key_share<T: Into<FrRepr>>(&self, i: T) -> SecretKey {
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pub fn secret_key_share<T: Into<FrRepr>>(&self, i: T) -> SecretKeyShare {
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SecretKey(self.poly.evaluate(from_repr_plus_1::<Fr>(i.into())))
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let value = self.poly.evaluate(from_repr_plus_1::<Fr>(i.into()));
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SecretKeyShare(SecretKey(value))
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}
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}
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/// Returns the corresponding public key set. That information can be shared publicly.
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/// Returns the corresponding public key set. That information can be shared publicly.
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@ -430,14 +508,14 @@ mod tests {
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let pk_set = sk_set.public_keys();
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let pk_set = sk_set.public_keys();
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// Make sure the keys are different, and the first coefficient is the main key.
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// Make sure the keys are different, and the first coefficient is the main key.
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assert_ne!(pk_set.public_key(), pk_set.public_key_share(0));
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assert_ne!(pk_set.public_key(), pk_set.public_key_share(0).0);
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assert_ne!(pk_set.public_key(), pk_set.public_key_share(1));
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assert_ne!(pk_set.public_key(), pk_set.public_key_share(1).0);
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assert_ne!(pk_set.public_key(), pk_set.public_key_share(2));
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assert_ne!(pk_set.public_key(), pk_set.public_key_share(2).0);
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// Make sure we don't hand out the main secret key to anyone.
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// Make sure we don't hand out the main secret key to anyone.
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assert_ne!(sk_set.secret_key(), sk_set.secret_key_share(0));
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assert_ne!(sk_set.secret_key(), sk_set.secret_key_share(0).0);
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assert_ne!(sk_set.secret_key(), sk_set.secret_key_share(1));
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assert_ne!(sk_set.secret_key(), sk_set.secret_key_share(1).0);
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assert_ne!(sk_set.secret_key(), sk_set.secret_key_share(2));
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assert_ne!(sk_set.secret_key(), sk_set.secret_key_share(2).0);
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let msg = "Totally real news";
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let msg = "Totally real news";
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