Interface Verifier

bitvm/src/signatures/winternitz.rs:135–189

Creates and verifies Winternitz signatures.

/// Creates and verifies Winternitz signatures.
pub trait Verifier {
    /// Creates a Winternitz signature for the given `secret_key` and `digits`.
    ///
    /// ## Output format
    ///
    /// - `hash(digits[0])`
    /// - `digits[0]`
    /// - `hash(digits[1])`
    /// - `digits[1]`
    /// - ...
    /// - `hash(digits[n + m - 1])`
    /// - `digits[n + m - 1]`
    ///
    /// There are `n` message digits followed by `m` checksum digits.
    /// The checksum is computed internally.
    fn sign_digits(ps: &Parameters, secret_key: &SecretKey, message_digits: Vec<u32>) -> Witness {
        let digits = add_message_checksum(ps, message_digits);
        let mut result = Witness::new();
        for i in 0..ps.total_digit_len() {
            let sig = digit_signature(secret_key, i, digits[i as usize]);
            // FIXME: Do trailing zeroes violate Bitcoin Script's minimum data push requirement?
            //        Maybe the script! macro removes the zeroes.
            //        There is a 1/256 chance that a signature contains a trailing zero.
            result.push(sig);
            result.push(bitcoin_representation(digits[i as usize] as i32));
        }
        result
    }

    /// Returns a Bitcoin script that verifies a Winternitz signature for the given `public_key`.
    ///
    /// The checksum is verified by a separate Bitcoin script.
    ///
    /// ## Precondition
    ///
    /// - `hash(digits[0])`
    /// - `digits[0]`
    /// - `hash(digits[1])`
    /// - `digits[1]`
    /// - ...
    /// - `hash(digits[n + m - 1])`
    /// - `digits[n + m - 1]` (stack top)
    ///
    /// For `n` message digits followed by `m` checksum digits.
    ///
    /// ## Postcondition
    ///
    /// - `digits[n + m - 1]`
    /// - `digits[n + m - 2]`
    /// - ...
    /// - `digits[0]` (alt stack top)
    ///
    /// The input is consumed from the stack.
    fn verify_digits(ps: &Parameters, public_key: &PublicKey) -> Script;
}

/// Converts the message on the stack after signature verification.
pub trait Converter {