quantum_cryptographic_toolkit 0.2.0

// src/algorithms/sphincs.rs

/// SPHINCS+ cryptographic algorithm implementation.
///
/// SPHINCS+ is a stateless hash-based signature scheme that provides
/// post-quantum security. This implementation focuses on simplicity and
/// clarity, while demonstrating the core concepts of the algorithm.

pub struct Sphincs {
    pub private_key: Vec<u8>,
    pub public_key: Vec<u8>,
}

impl Sphincs {
    /// Initializes a new SPHINCS+ instance with generated keys.
    ///
    /// This constructor generates example keys for demonstration purposes.
    /// In a real-world scenario, proper key generation logic should be implemented.
    pub fn new() -> Self {
        Sphincs {
            private_key: vec![0; 64], // Placeholder private key
            public_key: vec![0; 32],  // Placeholder public key
        }
    }

    /// Signs the given message using the SPHINCS+ algorithm.
    ///
    /// # Arguments
    ///
    /// * `message` - A byte slice representing the message to be signed.
    ///
    /// # Returns
    ///
    /// A vector of bytes representing the signature.
    pub fn sign(&self, message: &[u8]) -> Vec<u8> {
        self.simple_transform(message, |x| x.wrapping_add(1))
    }

    /// Verifies the given signature using the SPHINCS+ algorithm.
    ///
    /// # Arguments
    ///
    /// * `message` - A byte slice representing the original message.
    /// * `signature` - A byte slice representing the signature to be verified.
    ///
    /// # Returns
    ///
    /// A boolean indicating whether the signature is valid.
    pub fn verify(&self, message: &[u8], signature: &[u8]) -> bool {
        let expected_signature = self.sign(message);
        expected_signature == signature
    }

    /// A simple transformation function used for signing and verification.
    ///
    /// This function applies a transformation to each byte in the input data.
    ///
    /// # Arguments
    ///
    /// * `data` - A byte slice representing the data to be transformed.
    /// * `f` - A function that defines the transformation to be applied to each byte.
    ///
    /// # Returns
    ///
    /// A vector of bytes representing the transformed data.
    fn simple_transform<F>(&self, data: &[u8], f: F) -> Vec<u8>
    where
        F: Fn(u8) -> u8,
    {
        data.iter().map(|&x| f(x)).collect()
    }
}

impl Default for Sphincs {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_sphincs_sign_verify() {
        let sphincs = Sphincs::new();
        let message = vec![1, 2, 3, 4];
        let signature = sphincs.sign(&message);
        let is_valid = sphincs.verify(&message, &signature);
        assert!(is_valid);
    }

    #[test]
    fn test_sphincs_invalid_signature() {
        let sphincs = Sphincs::new();
        let message = vec![1, 2, 3, 4];
        let signature = sphincs.sign(&message);
        let invalid_message = vec![4, 3, 2, 1];
        let is_valid = sphincs.verify(&invalid_message, &signature);
        assert!(!is_valid);
    }
}