amaters_sdk_rust/

fhe.rs

//! FHE (Fully Homomorphic Encryption) key management and operations
//!
//! This module provides client-side encryption and decryption capabilities.
//! The actual FHE operations are feature-gated and require the `fhe` feature.

use crate::error::{Result, SdkError};
use amaters_core::{CipherBlob, Key};
use std::path::Path;

/// FHE client keys for encryption/decryption
///
/// In a real implementation, this would contain TFHE keys.
/// For now, this is a stub that will be implemented when the `fhe` feature is enabled.
#[derive(Clone)]
pub struct FheKeys {
    #[cfg(feature = "fhe")]
    _keys: tfhe::ClientKey,
    #[cfg(not(feature = "fhe"))]
    _placeholder: (),
}

impl FheKeys {
    /// Generate new FHE keys
    ///
    /// This is a computationally expensive operation (can take several seconds).
    pub fn generate() -> Result<Self> {
        #[cfg(feature = "fhe")]
        {
            // TODO: Implement with TFHE
            Err(SdkError::Fhe(
                "FHE key generation not yet implemented".to_string(),
            ))
        }
        #[cfg(not(feature = "fhe"))]
        {
            Ok(Self { _placeholder: () })
        }
    }

    /// Load keys from a file
    pub fn load_from_file(_path: impl AsRef<Path>) -> Result<Self> {
        #[cfg(feature = "fhe")]
        {
            // TODO: Implement with TFHE serialization
            Err(SdkError::Fhe(
                "FHE key loading not yet implemented".to_string(),
            ))
        }
        #[cfg(not(feature = "fhe"))]
        {
            Ok(Self { _placeholder: () })
        }
    }

    /// Save keys to a file
    pub fn save_to_file(&self, _path: impl AsRef<Path>) -> Result<()> {
        #[cfg(feature = "fhe")]
        {
            // TODO: Implement with TFHE serialization
            Err(SdkError::Fhe(
                "FHE key saving not yet implemented".to_string(),
            ))
        }
        #[cfg(not(feature = "fhe"))]
        {
            Ok(())
        }
    }

    /// Serialize keys to bytes
    #[cfg(feature = "serialization")]
    pub fn to_bytes(&self) -> Result<Vec<u8>> {
        #[cfg(feature = "fhe")]
        {
            // TODO: Implement with oxicode
            Err(SdkError::Fhe(
                "FHE key serialization not yet implemented".to_string(),
            ))
        }
        #[cfg(not(feature = "fhe"))]
        {
            Ok(Vec::new())
        }
    }

    /// Deserialize keys from bytes
    #[cfg(feature = "serialization")]
    pub fn from_bytes(_bytes: &[u8]) -> Result<Self> {
        #[cfg(feature = "fhe")]
        {
            // TODO: Implement with oxicode
            Err(SdkError::Fhe(
                "FHE key deserialization not yet implemented".to_string(),
            ))
        }
        #[cfg(not(feature = "fhe"))]
        {
            Ok(Self { _placeholder: () })
        }
    }
}

/// FHE encryptor for client-side encryption
pub struct FheEncryptor {
    keys: FheKeys,
}

impl FheEncryptor {
    /// Create a new encryptor with generated keys
    pub fn new() -> Result<Self> {
        Ok(Self {
            keys: FheKeys::generate()?,
        })
    }

    /// Create an encryptor with existing keys
    pub fn with_keys(keys: FheKeys) -> Self {
        Self { keys }
    }

    /// Get a reference to the keys
    pub fn keys(&self) -> &FheKeys {
        &self.keys
    }

    /// Encrypt a value
    ///
    /// For now, this is a placeholder that just wraps the plaintext.
    /// In production, this would use TFHE encryption.
    pub fn encrypt(&self, _plaintext: &[u8]) -> Result<CipherBlob> {
        #[cfg(feature = "fhe")]
        {
            // TODO: Implement with TFHE
            Err(SdkError::Fhe(
                "FHE encryption not yet implemented".to_string(),
            ))
        }
        #[cfg(not(feature = "fhe"))]
        {
            // For testing: just wrap the plaintext as-is
            // WARNING: This is NOT secure - only for development
            Ok(CipherBlob::new(_plaintext.to_vec()))
        }
    }

    /// Decrypt a ciphertext
    ///
    /// For now, this is a placeholder that just unwraps the data.
    /// In production, this would use TFHE decryption.
    pub fn decrypt(&self, ciphertext: &CipherBlob) -> Result<Vec<u8>> {
        #[cfg(feature = "fhe")]
        {
            // TODO: Implement with TFHE
            Err(SdkError::Fhe(
                "FHE decryption not yet implemented".to_string(),
            ))
        }
        #[cfg(not(feature = "fhe"))]
        {
            // For testing: just unwrap the data as-is
            // WARNING: This is NOT secure - only for development
            Ok(ciphertext.to_vec())
        }
    }

    /// Encrypt a key
    pub fn encrypt_key(&self, _key: &Key) -> Result<CipherBlob> {
        #[cfg(feature = "fhe")]
        {
            Err(SdkError::Fhe(
                "FHE key encryption not yet implemented".to_string(),
            ))
        }
        #[cfg(not(feature = "fhe"))]
        {
            // For testing: just wrap the key bytes
            Ok(CipherBlob::new(_key.to_vec()))
        }
    }

    /// Batch encrypt multiple values
    pub fn encrypt_batch(&self, plaintexts: &[&[u8]]) -> Result<Vec<CipherBlob>> {
        plaintexts.iter().map(|p| self.encrypt(p)).collect()
    }
}

impl Default for FheEncryptor {
    fn default() -> Self {
        Self::new().expect("failed to create default encryptor")
    }
}

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

    #[test]
    fn test_fhe_keys_stub() {
        // Without fhe feature, this should work as a placeholder
        #[cfg(not(feature = "fhe"))]
        {
            let keys = FheKeys::generate().expect("generate keys");
            let _saved = keys.save_to_file("/tmp/test_keys");
        }
    }

    #[test]
    fn test_encryptor_stub() {
        #[cfg(not(feature = "fhe"))]
        {
            let encryptor = FheEncryptor::new().expect("create encryptor");
            let plaintext = b"hello world";
            let ciphertext = encryptor.encrypt(plaintext).expect("encrypt");
            let decrypted = encryptor.decrypt(&ciphertext).expect("decrypt");

            // In stub mode, it should be identity
            assert_eq!(decrypted, plaintext);
        }
    }

    #[test]
    fn test_batch_encrypt() {
        #[cfg(not(feature = "fhe"))]
        {
            let encryptor = FheEncryptor::new().expect("create encryptor");
            let data: Vec<&[u8]> = vec![b"one", b"two", b"three"];

            let encrypted = encryptor.encrypt_batch(&data).expect("batch encrypt");
            assert_eq!(encrypted.len(), 3);
        }
    }
}