reddsa 0.5.2

A standalone implementation of the RedDSA signature scheme.
Documentation 
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//! Repairable Threshold Scheme
//!
//! Implements the Repairable Threshold Scheme (RTS) from <https://eprint.iacr.org/2017/1155>.
//! The RTS is used to help a signer (participant) repair their lost share. This is achieved
//! using a subset of the other signers know here as `helpers`.

use alloc::collections::BTreeMap;

use crate::frost::redpallas::{
    frost,
    keys::{KeyPackage, PublicKeyPackage},
    Ciphersuite, CryptoRng, Error, Identifier, PallasBlake2b512, RngCore,
};

/// A delta value which is the output of step 1 of RTS.
pub type Delta = frost::keys::repairable::Delta<PallasBlake2b512>;

/// A sigma value which is the output of step 2 of RTS.
pub type Sigma = frost::keys::repairable::Sigma<PallasBlake2b512>;

/// Step 1 of RTS.
///
/// Generates the "delta" values from the helper with `key_package_i` to send to
/// `helpers` (which includes the helper with `key_package_i`), to help
/// `participant` recover their share.
///
/// Returns a BTreeMap mapping which value should be sent to which participant.
pub fn repair_share_part1<C: Ciphersuite, R: RngCore + CryptoRng>(
    helpers: &[Identifier],
    key_package_i: &KeyPackage,
    rng: &mut R,
    participant: Identifier,
) -> Result<BTreeMap<Identifier, Delta>, Error> {
    frost::keys::repairable::repair_share_part1(helpers, key_package_i, rng, participant)
}

/// Step 2 of RTS.
///
/// Generates the "sigma" value from all `deltas` received from all helpers.
/// The "sigma" value must be sent to the participant repairing their share.
pub fn repair_share_part2(deltas: &[Delta]) -> Sigma {
    frost::keys::repairable::repair_share_part2::<PallasBlake2b512>(deltas)
}

/// Step 3 of RTS.
///
/// The participant with the given `identifier` recovers their `KeyPackage`
/// with the "sigma" values received from all helpers and the `PublicKeyPackage`
/// of the group (which can be sent by any of the helpers).
///
/// Returns an error if the `min_signers` field is not set in the `PublicKeyPackage`.
/// This happens for `PublicKeyPackage`s created before the 3.0.0 release;
/// in that case, the user should set the `min_signers` field manually.
pub fn repair_share_part3(
    sigmas: &[Sigma],
    identifier: Identifier,
    public_key_package: &PublicKeyPackage,
) -> Result<KeyPackage, Error> {
    frost::keys::repairable::repair_share_part3(sigmas, identifier, public_key_package)
}