Andreas Fackler
7 years ago
committed by
Vladimir Komendantskiy
parent
f8685b5367
commit
f6e01daa13
@ -0,0 +1,613 @@ |
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//! Utilities for distributed key generation.
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//!
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//! A `BivarPoly` can be used for Verifiable Secret Sharing (VSS) and for key generation by a
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//! trusted dealer. In a perfectly synchronous setting, e.g. on a blockchain or other agreed
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//! transaction log, it works like this:
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//!
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//! The dealer generates a `BivarPoly` of degree `t` and publishes the `BivariateCommitment`,
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//! with which the polynomial's values can be publicly verified. They then send _row_ `m > 0` to
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//! node number `m`. Node `m`, in turn, sends _value_ `s` to node number `s`. Then if `2 * t + 1`
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//! nodes confirm that they received a valid row, and there are at most `t` faulty nodes, then at
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//! least `t + 1` honest nodes sent on an entry of every other node's column to that node. So we
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//! know that every node can now reconstruct its column and the value at `0` of its column. These
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//! values all lie on a univariate polynomial of degree `t`, so they can be used as secret keys.
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//!
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//! For Distributed Key Generation (DKG), every node proposes a polynomial via VSS. After a fixed
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//! number (at least `N - 2 * t` if there are `N` nodes and up to `t` faulty ones) of them have
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//! successfully been distributed, every node adds up the resulting secrets. Since the sum of
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//! polynomials of degree `t` is itself a polynomial of degree `t`, these sums are still valid
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//! secret keys, but now nobody knows the master key (number `0`).
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// TODO: Expand this explanation and add examples, once the API is complete and stable.
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use std::borrow::Borrow; |
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use std::{cmp, iter, ops}; |
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use pairing::{CurveAffine, CurveProjective, Engine, Field, PrimeField}; |
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use rand::Rng; |
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/// A univariate polynomial in the prime field.
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#[derive(Clone, Debug)] |
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pub struct Poly<E: Engine> { |
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/// The coefficients of a polynomial.
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coeff: Vec<E::Fr>, |
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} |
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impl<E: Engine> PartialEq for Poly<E> { |
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fn eq(&self, other: &Self) -> bool { |
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self.coeff == other.coeff |
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} |
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} |
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impl<B: Borrow<Poly<E>>, E: Engine> ops::AddAssign<B> for Poly<E> { |
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fn add_assign(&mut self, rhs: B) { |
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let len = cmp::max(self.coeff.len(), rhs.borrow().coeff.len()); |
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self.coeff.resize(len, E::Fr::zero()); |
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for (self_c, rhs_c) in self.coeff.iter_mut().zip(&rhs.borrow().coeff) { |
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self_c.add_assign(rhs_c); |
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} |
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self.remove_zeros(); |
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} |
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} |
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impl<'a, B: Borrow<Poly<E>>, E: Engine> ops::Add<B> for &'a Poly<E> { |
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type Output = Poly<E>; |
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fn add(self, rhs: B) -> Poly<E> { |
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(*self).clone() + rhs |
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} |
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} |
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impl<B: Borrow<Poly<E>>, E: Engine> ops::Add<B> for Poly<E> { |
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type Output = Poly<E>; |
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fn add(mut self, rhs: B) -> Poly<E> { |
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self += rhs; |
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self |
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} |
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} |
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impl<B: Borrow<Poly<E>>, E: Engine> ops::SubAssign<B> for Poly<E> { |
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fn sub_assign(&mut self, rhs: B) { |
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let len = cmp::max(self.coeff.len(), rhs.borrow().coeff.len()); |
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self.coeff.resize(len, E::Fr::zero()); |
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for (self_c, rhs_c) in self.coeff.iter_mut().zip(&rhs.borrow().coeff) { |
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self_c.sub_assign(rhs_c); |
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} |
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self.remove_zeros(); |
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} |
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} |
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impl<'a, B: Borrow<Poly<E>>, E: Engine> ops::Sub<B> for &'a Poly<E> { |
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type Output = Poly<E>; |
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fn sub(self, rhs: B) -> Poly<E> { |
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(*self).clone() - rhs |
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} |
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} |
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impl<B: Borrow<Poly<E>>, E: Engine> ops::Sub<B> for Poly<E> { |
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type Output = Poly<E>; |
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fn sub(mut self, rhs: B) -> Poly<E> { |
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self -= rhs; |
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self |
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} |
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} |
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// Clippy thinks using any `+` and `-` in a `Mul` implementation is suspicious.
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#[cfg_attr(feature = "cargo-clippy", allow(suspicious_arithmetic_impl))] |
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impl<'a, B: Borrow<Poly<E>>, E: Engine> ops::Mul<B> for &'a Poly<E> { |
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type Output = Poly<E>; |
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fn mul(self, rhs: B) -> Self::Output { |
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let coeff = (0..(self.coeff.len() + rhs.borrow().coeff.len() - 1)) |
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.map(|i| { |
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let mut c = E::Fr::zero(); |
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for j in i.saturating_sub(rhs.borrow().degree())..(1 + cmp::min(i, self.degree())) { |
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let mut s = self.coeff[j]; |
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s.mul_assign(&rhs.borrow().coeff[i - j]); |
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c.add_assign(&s); |
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} |
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c |
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}) |
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.collect(); |
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Poly { coeff } |
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} |
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} |
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impl<B: Borrow<Poly<E>>, E: Engine> ops::Mul<B> for Poly<E> { |
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type Output = Poly<E>; |
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fn mul(self, rhs: B) -> Self::Output { |
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&self * rhs |
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} |
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} |
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impl<B: Borrow<Self>, E: Engine> ops::MulAssign<B> for Poly<E> { |
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fn mul_assign(&mut self, rhs: B) { |
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*self = &*self * rhs; |
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} |
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} |
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impl<E: Engine> Poly<E> { |
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/// Creates a random polynomial.
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pub fn random<R: Rng>(degree: usize, rng: &mut R) -> Self { |
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Poly { |
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coeff: (0..(degree + 1)).map(|_| rng.gen()).collect(), |
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} |
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} |
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/// Returns the polynomial with constant value `0`.
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pub fn zero() -> Self { |
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Poly { coeff: Vec::new() } |
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} |
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/// Returns the polynomial with constant value `1`.
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pub fn one() -> Self { |
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Self::monomial(0) |
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} |
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/// Returns the polynomial with constant value `c`.
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pub fn constant(c: E::Fr) -> Self { |
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Poly { coeff: vec![c] } |
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} |
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/// Returns the identity function, i.e. the polynomial "`x`".
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pub fn identity() -> Self { |
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Self::monomial(1) |
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} |
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/// Returns the (monic) monomial "`x.pow(degree)`".
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pub fn monomial(degree: usize) -> Self { |
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Poly { |
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coeff: iter::repeat(E::Fr::zero()) |
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.take(degree) |
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.chain(iter::once(E::Fr::one())) |
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.collect(), |
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} |
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} |
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/// Returns the unique polynomial `f` of degree `samples.len() - 1` with the given values
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/// `(x, f(x))`.
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pub fn interpolate<'a, T, I>(samples_repr: I) -> Self |
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where |
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I: IntoIterator<Item = (&'a T, &'a E::Fr)>, |
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T: Into<<E::Fr as PrimeField>::Repr> + Clone + 'a, |
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{ |
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let convert = |(x_repr, y): (&T, &E::Fr)| { |
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let x = E::Fr::from_repr(x_repr.clone().into()).expect("invalid index"); |
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(x, *y) |
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}; |
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let samples: Vec<(E::Fr, E::Fr)> = samples_repr.into_iter().map(convert).collect(); |
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Self::compute_interpolation(&samples) |
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} |
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/// Returns the degree.
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pub fn degree(&self) -> usize { |
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self.coeff.len() - 1 |
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} |
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/// Returns the value at the point `i`.
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pub fn evaluate<T: Into<<E::Fr as PrimeField>::Repr>>(&self, i: T) -> E::Fr { |
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let mut result = match self.coeff.last() { |
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None => return E::Fr::zero(), |
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Some(c) => *c, |
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}; |
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let x = E::Fr::from_repr(i.into()).expect("invalid index"); |
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for c in self.coeff.iter().rev().skip(1) { |
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result.mul_assign(&x); |
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result.add_assign(c); |
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} |
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result |
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} |
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/// Returns the corresponding commitment.
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pub fn commitment(&self) -> Commitment<E> { |
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let to_g1 = |c: &E::Fr| E::G1Affine::one().mul(*c); |
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Commitment { |
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coeff: self.coeff.iter().map(to_g1).collect(), |
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} |
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} |
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/// Removes all trailing zero coefficients.
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fn remove_zeros(&mut self) { |
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let zeros = self.coeff.iter().rev().take_while(|c| c.is_zero()).count(); |
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let len = self.coeff.len() - zeros; |
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self.coeff.truncate(len) |
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} |
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/// Returns the unique polynomial `f` of degree `samples.len() - 1` with the given values
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/// `(x, f(x))`.
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fn compute_interpolation(samples: &[(E::Fr, E::Fr)]) -> Self { |
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if samples.is_empty() { |
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return Poly::zero(); |
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} else if samples.len() == 1 { |
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return Poly::constant(samples[0].1); |
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} |
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// The degree is at least 1 now.
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let degree = samples.len() - 1; |
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// Interpolate all but the last sample.
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let prev = Self::compute_interpolation(&samples[..degree]); |
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let (x, mut y) = samples[degree]; // The last sample.
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y.sub_assign(&prev.evaluate(x)); |
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let step = Self::lagrange(x, &samples[..degree]); |
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prev + step * Self::constant(y) |
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} |
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/// Returns the Lagrange base polynomial that is `1` in `p` and `0` in every `samples[i].0`.
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fn lagrange(p: E::Fr, samples: &[(E::Fr, E::Fr)]) -> Self { |
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let mut result = Self::one(); |
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for &(sx, _) in samples { |
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let mut denom = p; |
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denom.sub_assign(&sx); |
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denom = denom.inverse().expect("sample points must be distinct"); |
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result *= (Self::identity() - Self::constant(sx)) * Self::constant(denom); |
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} |
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result |
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} |
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} |
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/// A commitment to a univariate polynomial.
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#[derive(Debug, Clone)] |
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#[cfg_attr(feature = "serialization-serde", derive(Serialize, Deserialize))] |
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pub struct Commitment<E: Engine> { |
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/// The coefficients of the polynomial.
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#[cfg_attr(feature = "serialization-serde", serde(with = "super::serde_impl::projective_vec"))] |
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coeff: Vec<E::G1>, |
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} |
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impl<E: Engine> PartialEq for Commitment<E> { |
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fn eq(&self, other: &Self) -> bool { |
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self.coeff == other.coeff |
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} |
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} |
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impl<B: Borrow<Commitment<E>>, E: Engine> ops::AddAssign<B> for Commitment<E> { |
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fn add_assign(&mut self, rhs: B) { |
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let len = cmp::max(self.coeff.len(), rhs.borrow().coeff.len()); |
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self.coeff.resize(len, E::G1::zero()); |
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for (self_c, rhs_c) in self.coeff.iter_mut().zip(&rhs.borrow().coeff) { |
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self_c.add_assign(rhs_c); |
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} |
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self.remove_zeros(); |
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} |
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} |
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impl<'a, B: Borrow<Commitment<E>>, E: Engine> ops::Add<B> for &'a Commitment<E> { |
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type Output = Commitment<E>; |
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fn add(self, rhs: B) -> Commitment<E> { |
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(*self).clone() + rhs |
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} |
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} |
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impl<B: Borrow<Commitment<E>>, E: Engine> ops::Add<B> for Commitment<E> { |
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type Output = Commitment<E>; |
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fn add(mut self, rhs: B) -> Commitment<E> { |
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self += rhs; |
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self |
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} |
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} |
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impl<E: Engine> Commitment<E> { |
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/// Returns the polynomial's degree.
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pub fn degree(&self) -> usize { |
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self.coeff.len() - 1 |
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} |
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/// Returns the `i`-th public key share.
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pub fn evaluate<T: Into<<E::Fr as PrimeField>::Repr>>(&self, i: T) -> E::G1 { |
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let mut result = match self.coeff.last() { |
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None => return E::G1::zero(), |
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Some(c) => *c, |
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}; |
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let x = E::Fr::from_repr(i.into()).expect("invalid index"); |
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for c in self.coeff.iter().rev().skip(1) { |
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result.mul_assign(x); |
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result.add_assign(c); |
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} |
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result |
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} |
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/// Removes all trailing zero coefficients.
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fn remove_zeros(&mut self) { |
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let zeros = self.coeff.iter().rev().take_while(|c| c.is_zero()).count(); |
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let len = self.coeff.len() - zeros; |
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self.coeff.truncate(len) |
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} |
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} |
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/// A symmetric bivariate polynomial in the prime field.
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///
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/// This can be used for Verifiable Secret Sharing and Distributed Key Generation. See the module
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/// documentation for details.
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#[derive(Debug, Clone)] |
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pub struct BivarPoly<E: Engine> { |
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/// The polynomial's degree in each of the two variables.
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degree: usize, |
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/// The coefficients of the polynomial. Coefficient `(i, j)` for `i <= j` is in position
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/// `j * (j + 1) / 2 + i`.
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coeff: Vec<E::Fr>, |
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} |
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impl<E: Engine> BivarPoly<E> { |
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/// Creates a random polynomial.
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pub fn random<R: Rng>(degree: usize, rng: &mut R) -> Self { |
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BivarPoly { |
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degree, |
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coeff: (0..coeff_pos(degree + 1, 0)).map(|_| rng.gen()).collect(), |
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} |
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} |
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/// Returns the polynomial's degree: It is the same in both variables.
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pub fn degree(&self) -> usize { |
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self.degree |
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} |
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/// Returns the polynomial's value at the point `(x, y)`.
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pub fn evaluate<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x: T, y: T) -> E::Fr { |
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let x_pow = self.powers(x); |
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let y_pow = self.powers(y); |
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// TODO: Can we save a few multiplication steps here due to the symmetry?
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let mut result = E::Fr::zero(); |
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for (i, x_pow_i) in x_pow.into_iter().enumerate() { |
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for (j, y_pow_j) in y_pow.iter().enumerate() { |
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let mut summand = self.coeff[coeff_pos(i, j)]; |
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summand.mul_assign(&x_pow_i); |
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summand.mul_assign(y_pow_j); |
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result.add_assign(&summand); |
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} |
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} |
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result |
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} |
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/// Returns the `x`-th row, as a univariate polynomial.
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pub fn row<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x: T) -> Poly<E> { |
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let x_pow = self.powers(x); |
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let coeff: Vec<E::Fr> = (0..=self.degree) |
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.map(|i| { |
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let mut result = E::Fr::zero(); |
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for (j, x_pow_j) in x_pow.iter().enumerate() { |
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let mut summand = self.coeff[coeff_pos(i, j)]; |
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summand.mul_assign(x_pow_j); |
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result.add_assign(&summand); |
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} |
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result |
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}) |
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.collect(); |
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Poly { coeff } |
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} |
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/// Returns the corresponding commitment. That information can be shared publicly.
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pub fn commitment(&self) -> BivarCommitment<E> { |
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let to_pub = |c: &E::Fr| E::G1Affine::one().mul(*c); |
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BivarCommitment { |
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degree: self.degree, |
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coeff: self.coeff.iter().map(to_pub).collect(), |
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} |
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} |
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/// Returns the `0`-th to `degree`-th power of `x`.
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fn powers<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x_repr: T) -> Vec<E::Fr> { |
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powers(x_repr, self.degree) |
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} |
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} |
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/// A commitment to a bivariate polynomial.
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#[derive(Debug, Clone)] |
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#[cfg_attr(feature = "serialization-serde", derive(Serialize, Deserialize))] |
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pub struct BivarCommitment<E: Engine> { |
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/// The polynomial's degree in each of the two variables.
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degree: usize, |
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/// The commitments to the coefficients.
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#[cfg_attr(feature = "serialization-serde", serde(with = "super::serde_impl::projective_vec"))] |
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coeff: Vec<E::G1>, |
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} |
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impl<E: Engine> BivarCommitment<E> { |
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/// Returns the polynomial's degree: It is the same in both variables.
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pub fn degree(&self) -> usize { |
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self.degree |
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} |
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|
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/// Returns the commitment's value at the point `(x, y)`.
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pub fn evaluate<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x: T, y: T) -> E::G1 { |
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let x_pow = self.powers(x); |
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let y_pow = self.powers(y); |
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// TODO: Can we save a few multiplication steps here due to the symmetry?
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let mut result = E::G1::zero(); |
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for (i, x_pow_i) in x_pow.into_iter().enumerate() { |
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for (j, y_pow_j) in y_pow.iter().enumerate() { |
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let mut summand = self.coeff[coeff_pos(i, j)]; |
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summand.mul_assign(x_pow_i); |
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summand.mul_assign(*y_pow_j); |
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result.add_assign(&summand); |
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} |
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} |
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result |
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} |
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|
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/// Returns the `x`-th row, as a commitment to a univariate polynomial.
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pub fn row<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x: T) -> Commitment<E> { |
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let x_pow = self.powers(x); |
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let coeff: Vec<E::G1> = (0..=self.degree) |
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.map(|i| { |
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let mut result = E::G1::zero(); |
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for (j, x_pow_j) in x_pow.iter().enumerate() { |
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let mut summand = self.coeff[coeff_pos(i, j)]; |
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summand.mul_assign(*x_pow_j); |
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result.add_assign(&summand); |
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} |
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result |
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}) |
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.collect(); |
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Commitment { coeff } |
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} |
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/// Returns the `0`-th to `degree`-th power of `x`.
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fn powers<T: Into<<E::Fr as PrimeField>::Repr>>(&self, x_repr: T) -> Vec<E::Fr> { |
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powers(x_repr, self.degree) |
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} |
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} |
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/// Returns the `0`-th to `degree`-th power of `x`.
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fn powers<P: PrimeField, T: Into<P::Repr>>(x_repr: T, degree: usize) -> Vec<P> { |
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let x = &P::from_repr(x_repr.into()).expect("invalid index"); |
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let mut x_pow_i = P::one(); |
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iter::once(x_pow_i) |
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.chain((0..degree).map(|_| { |
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x_pow_i.mul_assign(x); |
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x_pow_i |
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})) |
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.collect() |
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} |
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|
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/// Returns the position of coefficient `(i, j)` in the vector describing a symmetric bivariate
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/// polynomial.
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fn coeff_pos(i: usize, j: usize) -> usize { |
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// Since the polynomial is symmetric, we can order such that `j >= i`.
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if j >= i { |
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j * (j + 1) / 2 + i |
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} else { |
||||
i * (i + 1) / 2 + j |
||||
} |
||||
} |
||||
|
||||
#[cfg(test)] |
||||
mod tests { |
||||
use std::collections::BTreeMap; |
||||
|
||||
use super::{coeff_pos, BivarPoly, Poly}; |
||||
|
||||
use pairing::bls12_381::Bls12; |
||||
use pairing::{CurveAffine, Engine, Field, PrimeField}; |
||||
use rand; |
||||
|
||||
type Fr = <Bls12 as Engine>::Fr; |
||||
|
||||
fn fr(x: i64) -> Fr { |
||||
let mut result = Fr::from_repr((x.abs() as u64).into()).unwrap(); |
||||
if x < 0 { |
||||
result.negate(); |
||||
} |
||||
result |
||||
} |
||||
|
||||
#[test] |
||||
fn test_coeff_pos() { |
||||
let mut i = 0; |
||||
let mut j = 0; |
||||
for n in 0..100 { |
||||
assert_eq!(n, coeff_pos(i, j)); |
||||
if i >= j { |
||||
j += 1; |
||||
i = 0; |
||||
} else { |
||||
i += 1; |
||||
} |
||||
} |
||||
} |
||||
|
||||
#[test] |
||||
fn poly() { |
||||
// The polynomial "`5 * x.pow(3) + x.pow(1) - 2`".
|
||||
let poly: Poly<Bls12> = |
||||
Poly::monomial(3) * Poly::constant(fr(5)) + Poly::monomial(1) - Poly::constant(fr(2)); |
||||
let coeff = vec![fr(-2), fr(1), fr(0), fr(5)]; |
||||
assert_eq!(Poly { coeff }, poly); |
||||
let samples = vec![ |
||||
(fr(-1), fr(-8)), |
||||
(fr(2), fr(40)), |
||||
(fr(3), fr(136)), |
||||
(fr(5), fr(628)), |
||||
]; |
||||
for &(x, y) in &samples { |
||||
assert_eq!(y, poly.evaluate(x)); |
||||
} |
||||
let sample_iter = samples.iter().map(|&(ref x, ref y)| (x, y)); |
||||
assert_eq!(Poly::interpolate(sample_iter), poly); |
||||
} |
||||
|
||||
#[test] |
||||
fn distributed_key_generation() { |
||||
let mut rng = rand::thread_rng(); |
||||
let dealer_num = 3; |
||||
let node_num = 5; |
||||
let faulty_num = 2; |
||||
|
||||
// For distributed key generation, a number of dealers, only one of who needs to be honest,
|
||||
// generates random bivariate polynomials and publicly commits to them. In partice, the
|
||||
// dealers can e.g. be any `faulty_num + 1` nodes.
|
||||
let bi_polys: Vec<BivarPoly<Bls12>> = (0..dealer_num) |
||||
.map(|_| BivarPoly::random(faulty_num, &mut rng)) |
||||
.collect(); |
||||
let pub_bi_commits: Vec<_> = bi_polys.iter().map(BivarPoly::commitment).collect(); |
||||
|
||||
let mut sec_keys = vec![fr(0); node_num]; |
||||
|
||||
// Each dealer sends row `m` to node `m`, where the index starts at `1`. Don't send row `0`
|
||||
// to anyone! The nodes verify their rows, and send _value_ `s` on to node `s`. They again
|
||||
// verify the values they received, and collect them.
|
||||
for (bi_poly, bi_commit) in bi_polys.iter().zip(&pub_bi_commits) { |
||||
for m in 1..=node_num { |
||||
// Node `m` receives its row and verifies it.
|
||||
let row_poly = bi_poly.row(m as u64); |
||||
let row_commit = bi_commit.row(m as u64); |
||||
assert_eq!(row_poly.commitment(), row_commit); |
||||
// Node `s` receives the `s`-th value and verifies it.
|
||||
for s in 1..=node_num { |
||||
let val = row_poly.evaluate(s as u64); |
||||
let val_g1 = <Bls12 as Engine>::G1Affine::one().mul(val); |
||||
assert_eq!(bi_commit.evaluate(m as u64, s as u64), val_g1); |
||||
// The node can't verify this directly, but it should have the correct value:
|
||||
assert_eq!(bi_poly.evaluate(m as u64, s as u64), val); |
||||
} |
||||
|
||||
// A cheating dealer who modified the polynomial would be detected.
|
||||
let wrong_poly = row_poly.clone() + Poly::monomial(2) * Poly::constant(fr(5)); |
||||
assert_ne!(wrong_poly.commitment(), row_commit); |
||||
|
||||
// If `2 * faulty_num + 1` nodes confirm that they received a valid row, then at
|
||||
// least `faulty_num + 1` honest ones did, and sent the correct values on to node
|
||||
// `s`. So every node received at least `faulty_num + 1` correct entries of their
|
||||
// column/row (remember that the bivariate polynomial is symmetric). They can
|
||||
// reconstruct the full row and in particular value `0` (which no other node knows,
|
||||
// only the dealer). E.g. let's say nodes `1`, `2` and `4` are honest. Then node
|
||||
// `m` received three correct entries from that row:
|
||||
let received: BTreeMap<_, _> = [1, 2, 4] |
||||
.iter() |
||||
.map(|&i| (i, bi_poly.evaluate(m as u64, i as u64))) |
||||
.collect(); |
||||
let my_row = Poly::interpolate(&received); |
||||
assert_eq!(bi_poly.evaluate(m as u64, 0), my_row.evaluate(0)); |
||||
assert_eq!(row_poly, my_row); |
||||
|
||||
// The node sums up all values number `0` it received from the different dealer. No
|
||||
// dealer and no other node knows the sum in the end.
|
||||
sec_keys[m - 1].add_assign(&my_row.evaluate(0)); |
||||
} |
||||
} |
||||
|
||||
// Each node now adds up all the first values of the rows it received from the different
|
||||
// dealers (excluding the dealers where fewer than `2 * faulty_num + 1` nodes confirmed).
|
||||
// The whole first column never gets added up in practice, because nobody has all the
|
||||
// information. We do it anyway here; entry `0` is the secret key that is not known to
|
||||
// anyone, neither a dealer, nor a node:
|
||||
let mut sec_key_set = Poly::zero(); |
||||
for bi_poly in &bi_polys { |
||||
sec_key_set += bi_poly.row(0); |
||||
} |
||||
for m in 1..=node_num { |
||||
assert_eq!(sec_key_set.evaluate(m as u64), sec_keys[m - 1]); |
||||
} |
||||
|
||||
// The sum of the first rows of the public commitments is the commitment to the secret key
|
||||
// set.
|
||||
let mut sum_commit = Poly::zero().commitment(); |
||||
for bi_commit in &pub_bi_commits { |
||||
sum_commit += bi_commit.row(0); |
||||
} |
||||
assert_eq!(sum_commit, sec_key_set.commitment()); |
||||
} |
||||
} |
||||
@ -0,0 +1,119 @@ |
||||
use std::borrow::Borrow; |
||||
use std::marker::PhantomData; |
||||
|
||||
use pairing::{CurveAffine, CurveProjective, EncodedPoint, Engine}; |
||||
|
||||
use super::{DecryptionShare, PublicKey, Signature}; |
||||
use serde::de::Error as DeserializeError; |
||||
use serde::{Deserialize, Deserializer, Serialize, Serializer}; |
||||
|
||||
const ERR_LEN: &str = "wrong length of deserialized group element"; |
||||
const ERR_CODE: &str = "deserialized bytes don't encode a group element"; |
||||
|
||||
/// A wrapper type to facilitate serialization and deserialization of group elements.
|
||||
struct CurveWrap<C, B>(B, PhantomData<C>); |
||||
|
||||
impl<C, B> CurveWrap<C, B> { |
||||
fn new(c: B) -> Self { |
||||
CurveWrap(c, PhantomData) |
||||
} |
||||
} |
||||
|
||||
impl<C: CurveProjective, B: Borrow<C>> Serialize for CurveWrap<C, B> { |
||||
fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> { |
||||
serialize_projective(self.0.borrow(), s) |
||||
} |
||||
} |
||||
|
||||
impl<'de, C: CurveProjective> Deserialize<'de> for CurveWrap<C, C> { |
||||
fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> { |
||||
Ok(CurveWrap::new(deserialize_projective(d)?)) |
||||
} |
||||
} |
||||
|
||||
impl<E: Engine> Serialize for PublicKey<E> { |
||||
fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> { |
||||
serialize_projective(&self.0, s) |
||||
} |
||||
} |
||||
|
||||
impl<'de, E: Engine> Deserialize<'de> for PublicKey<E> { |
||||
fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> { |
||||
Ok(PublicKey(deserialize_projective(d)?)) |
||||
} |
||||
} |
||||
|
||||
impl<E: Engine> Serialize for Signature<E> { |
||||
fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> { |
||||
serialize_projective(&self.0, s) |
||||
} |
||||
} |
||||
|
||||
impl<'de, E: Engine> Deserialize<'de> for Signature<E> { |
||||
fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> { |
||||
Ok(Signature(deserialize_projective(d)?)) |
||||
} |
||||
} |
||||
|
||||
impl<E: Engine> Serialize for DecryptionShare<E> { |
||||
fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> { |
||||
serialize_projective(&self.0, s) |
||||
} |
||||
} |
||||
|
||||
impl<'de, E: Engine> Deserialize<'de> for DecryptionShare<E> { |
||||
fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error> { |
||||
Ok(DecryptionShare(deserialize_projective(d)?)) |
||||
} |
||||
} |
||||
|
||||
/// Serializes the compressed representation of a group element.
|
||||
fn serialize_projective<S, C>(c: &C, s: S) -> Result<S::Ok, S::Error> |
||||
where |
||||
S: Serializer, |
||||
C: CurveProjective, |
||||
{ |
||||
c.into_affine().into_compressed().as_ref().serialize(s) |
||||
} |
||||
|
||||
/// Deserializes the compressed representation of a group element.
|
||||
fn deserialize_projective<'de, D, C>(d: D) -> Result<C, D::Error> |
||||
where |
||||
D: Deserializer<'de>, |
||||
C: CurveProjective, |
||||
{ |
||||
let bytes = <Vec<u8>>::deserialize(d)?; |
||||
if bytes.len() != <C::Affine as CurveAffine>::Compressed::size() { |
||||
return Err(D::Error::custom(ERR_LEN)); |
||||
} |
||||
let mut compressed = <C::Affine as CurveAffine>::Compressed::empty(); |
||||
compressed.as_mut().copy_from_slice(&bytes); |
||||
let to_err = |_| D::Error::custom(ERR_CODE); |
||||
Ok(compressed.into_affine().map_err(to_err)?.into_projective()) |
||||
} |
||||
|
||||
/// Serialization and deserialization of vectors of projective curve elements.
|
||||
pub mod projective_vec { |
||||
use super::CurveWrap; |
||||
|
||||
use pairing::CurveProjective; |
||||
use serde::{Deserialize, Deserializer, Serialize, Serializer}; |
||||
|
||||
pub fn serialize<S, C>(vec: &[C], s: S) -> Result<S::Ok, S::Error> |
||||
where |
||||
S: Serializer, |
||||
C: CurveProjective, |
||||
{ |
||||
let wrap_vec: Vec<CurveWrap<C, &C>> = vec.iter().map(CurveWrap::new).collect(); |
||||
wrap_vec.serialize(s) |
||||
} |
||||
|
||||
pub fn deserialize<'de, D, C>(d: D) -> Result<Vec<C>, D::Error> |
||||
where |
||||
D: Deserializer<'de>, |
||||
C: CurveProjective, |
||||
{ |
||||
let wrap_vec = <Vec<CurveWrap<C, C>>>::deserialize(d)?; |
||||
Ok(wrap_vec.into_iter().map(|CurveWrap(c, _)| c).collect()) |
||||
} |
||||
} |
||||
Loading…
Reference in new issue