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86 lines
2.4 KiB
Rust
86 lines
2.4 KiB
Rust
#![cfg_attr(docsrs, feature(doc_cfg))]
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#![doc = include_str!("../README.md")]
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#![no_std]
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use core::ops::{Deref, DerefMut};
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extern crate alloc;
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use alloc::vec::Vec;
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use zeroize::Zeroizing;
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use ciphersuite::{GroupIo, Id};
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pub use dkg::*;
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/// Errors encountered when recovering a secret-shared key from a collection of
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/// `dkg::ThresholdKeys`.
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#[derive(Clone, PartialEq, Eq, Debug, thiserror::Error)]
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pub enum RecoveryError {
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/// No keys were provided.
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#[error("no keys provided")]
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NoKeysProvided,
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/// Not enough keys were provided.
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#[error("not enough keys provided (threshold required {required}, provided {provided})")]
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NotEnoughKeysProvided { required: u16, provided: usize },
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/// The keys had inconsistent parameters.
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#[error("keys had inconsistent parameters")]
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InconsistentParameters,
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/// The keys are from distinct secret-sharing sessions or otherwise corrupt.
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#[error("recovery failed")]
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Failure,
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/// An error propagated from the underlying `dkg` crate.
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#[error("error from dkg ({0})")]
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DkgError(DkgError),
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}
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/// Recover a shared secret from a collection of `dkg::ThresholdKeys`.
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pub fn recover_key<C: GroupIo + Id>(
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keys: &[ThresholdKeys<C>],
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) -> Result<Zeroizing<C::F>, RecoveryError> {
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let included = keys.iter().map(|keys| keys.params().i()).collect::<Vec<_>>();
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let keys_len = keys.len();
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let mut keys = keys.iter();
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let first_keys = keys.next().ok_or(RecoveryError::NoKeysProvided)?;
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{
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let t = first_keys.params().t();
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if keys_len < usize::from(t) {
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Err(RecoveryError::NotEnoughKeysProvided { required: t, provided: keys_len })?;
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}
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}
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{
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let first_params = (
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first_keys.params().t(),
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first_keys.params().n(),
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first_keys.group_key(),
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first_keys.current_scalar(),
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first_keys.current_offset(),
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);
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for keys in keys.clone() {
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let params = (
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keys.params().t(),
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keys.params().n(),
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keys.group_key(),
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keys.current_scalar(),
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keys.current_offset(),
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);
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if params != first_params {
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Err(RecoveryError::InconsistentParameters)?;
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}
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}
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}
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let mut res: Zeroizing<_> =
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first_keys.view(included.clone()).map_err(RecoveryError::DkgError)?.secret_share().clone();
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for keys in keys {
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*res.deref_mut() +=
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keys.view(included.clone()).map_err(RecoveryError::DkgError)?.secret_share().deref();
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}
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if (C::generator() * res.deref()) != first_keys.group_key() {
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Err(RecoveryError::Failure)?;
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}
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Ok(res)
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}
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