stwo 2.3.0

Core library implementing the Circle STARK prover and verifier
Documentation 
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//! Implements a FRI polynomial commitment scheme.
//!
//! This is a protocol where the prover can commit on a set of polynomials and then prove their
//! opening on a set of points.
//! Note: This implementation is not really a polynomial commitment scheme, because we are not in
//! the unique decoding regime. This is enough for a STARK proof though, where we only want to imply
//! the existence of such polynomials, and are ok with having a small decoding list.
//! Note: Opened points cannot come from the commitment domain.

pub mod quotients;
pub mod utils;
mod verifier;

use serde::{Deserialize, Serialize};

pub use self::utils::TreeVec;
pub use self::verifier::CommitmentSchemeVerifier;
use super::channel::Channel;
use super::fields::qm31::SecureField;
use super::fri::FriConfig;

#[derive(Copy, Debug, Clone, PartialEq, Eq)]
pub struct TreeSubspan {
    pub tree_index: usize,
    pub col_start: usize,
    pub col_end: usize,
}

#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
/// Configuration parameters for the committment scheme prover.
pub struct PcsConfig {
    /// The number of proof of work bits before the FRI queries.
    pub pow_bits: u32,
    pub fri_config: FriConfig,
    /// An optional integer which controls the size of the lifting domain (This size includes the
    /// `log_blowup_factor`). When specified, the prover lifts all polynomials to the domain of
    /// given log size.
    /// If `None`, the prover lifts each tree’s polynomials to the largest domain within that tree
    /// (an implicit assumption here is that the largest domains are all of equal size across
    /// trees, except possibly for the preprocessed tree).
    pub lifting_log_size: Option<u32>,
}
impl PcsConfig {
    pub const fn security_bits(&self) -> u32 {
        self.pow_bits + self.fri_config.security_bits()
    }

    pub fn mix_into(&self, channel: &mut impl Channel) {
        let PcsConfig {
            pow_bits,
            fri_config,
            lifting_log_size,
        } = self;
        let FriConfig {
            log_blowup_factor,
            n_queries,
            log_last_layer_degree_bound,
            fold_step,
        } = fri_config;

        channel.mix_felts(&[
            SecureField::from_u32_unchecked(
                *pow_bits,
                *log_blowup_factor,
                *n_queries as u32,
                *log_last_layer_degree_bound,
            ),
            SecureField::from_u32_unchecked(*fold_step, lifting_log_size.unwrap_or(0), 0, 0),
        ]);
    }
}

impl Default for PcsConfig {
    fn default() -> Self {
        Self {
            pow_bits: 10,
            fri_config: FriConfig::new(0, 1, 3, 1),
            lifting_log_size: None,
        }
    }
}

#[cfg(test)]
mod tests {
    #[test]
    fn test_security_bits() {
        let config = super::PcsConfig {
            pow_bits: 42,
            fri_config: super::FriConfig::new(10, 10, 70, 1),
            lifting_log_size: None,
        };
        assert!(config.security_bits() == 10 * 70 + 42);
    }
}