dmsc 0.1.9

//! Copyright © 2025-2026 Wenze Wei. All Rights Reserved.
//!
//! This file is part of Ri.
//! The Ri project belongs to the Dunimd Team.
//!
//! Licensed under the Apache License, Version 2.0 (the "License");
//! You may not use this file except in compliance with the License.
//! You may obtain a copy of the License at
//!
//!     http://www.apache.org/licenses/LICENSE-2.0
//!
//! Unless required by applicable law or agreed to in writing, software
//! distributed under the License is distributed on an "AS IS" BASIS,
//! WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//! See the License for the specific language governing permissions and
//! limitations under the License.

#![allow(non_snake_case)]

//! # Protocol Security Module
//! 
//! This module provides comprehensive security features for the private protocol,
//! including quantum-resistant cryptography, device authentication, traffic
//! obfuscation, and anti-forensic capabilities.
//! 
//! ## Security Components
//! 
//! - **RiCryptoSuite**: Cryptographic algorithm selection
//! - **RiDeviceAuthProtocol**: Hardware-based device authentication
//! - **RiPostQuantumCrypto**: Quantum-resistant key exchange and encryption
//! - **RiObfuscationLayer**: Traffic pattern obfuscation
//! - **RiNationalCrypto**: National cryptographic standards (SM2/SM3/SM4)
//! - **RiAntiForensic**: Anti-forensic and anti-analysis features
//! 
//! ## Cryptographic Algorithms
//! 
//! ### National Standard Suite (SM Series)
//! - **SM2**: Elliptic curve digital signature algorithm
//! - **SM3**: Cryptographic hash function
//! - **SM4**: Block cipher algorithm
//! 
//! ### Post-Quantum Suite
//! - **Kyber**: Key encapsulation mechanism
//! - **Dilithium**: Digital signature algorithm
//! - **Falcon**: Compact digital signature algorithm
//! 
//! ### International Suite
//! - **AES-256**: Advanced encryption standard
//! - **SHA-3**: Secure hash algorithm
//! - **ECDSA**: Elliptic curve digital signature
//! 
//! ## Security Levels
//! 
//! - **Basic**: Standard AES-256 encryption
//! - **High**: National standard algorithms + device auth
//! - **Maximum**: Post-quantum algorithms + maximum obfuscation
//! 
//! ## Usage Examples
//! 
//! ```rust
//! use ri::protocol::security::{RiCryptoSuite, RiDeviceAuthProtocol, RiPostQuantumCrypto};
//! 
//! async fn example() -> RiResult<()> {
//!     // Initialize device authentication
//!     let device_auth = RiDeviceAuthProtocol::new();
//!     device_auth.initialize().await?;
//!     
//!     // Perform quantum-resistant key exchange
//!     let post_quantum = RiPostQuantumCrypto::new();
//!     post_quantum.initialize(&RiCryptoSuite::PostQuantum).await?;
//!     
//!     // Authenticate device
//!     device_auth.authenticate_device("target-device").await?;
//!     
//!     Ok(())
//! }
//! ```

use std::collections::HashMap as FxHashMap;
use std::sync::Arc;
use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
use async_trait::async_trait;
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::net::TcpStream;
use tokio::sync::RwLock;
use rand::Rng;

use crate::core::{RiResult, RiError};
use super::RiProtocolConfig;

/// Cryptographic suite enumeration for protocol security configuration.
///
/// This enumeration defines available cryptographic algorithm suites that can be used
/// to secure protocol communications. Each suite represents a different security level
/// and compliance requirement, allowing organizations to select appropriate algorithms
/// based on their security policies and regulatory requirements.
///
/// ## Suite Selection Guidelines
///
/// - **NationalStandard**: Required for government and financial institutions in China
///   that must comply with Chinese cryptographic regulations
/// - **International**: Suitable for cross-border communications requiring globally
///   recognized algorithms like AES-256 and ECDSA
/// - **PostQuantum**: Recommended for long-term data protection against quantum
///   computer attacks on current cryptographic systems
/// - **Hybrid**: Provides defense-in-depth by combining multiple algorithm families
///
/// ## Security Level Comparison
///
/// | Suite | Level | Quantum Resistance | Compliance |
/// |-------|-------|-------------------|------------|
/// | NationalStandard | 8 | No | CN Regulations |
/// | International | 7 | No | Global Standards |
/// | PostQuantum | 10 | Yes | Future-Proof |
/// | Hybrid | 9 | Partial | Multi-Framework |
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[cfg_attr(feature = "pyo3", pyo3::prelude::pyclass)]
pub enum RiCryptoSuite {
    /// National cryptographic standards (SM2/SM3/SM4)
    ///
    /// Implements Chinese National Standard cryptographic algorithms required for
    /// commercial applications within China. This suite provides strong encryption
    /// compliant with GB/T 32907-2016 (SM4), GB/T 32918-2016 (SM2), and
    /// GM/T 0004-2012 (SM3).
    NationalStandard,
    /// Post-quantum cryptography (Kyber/Dilithium/Falcon)
    ///
    /// Provides quantum-resistant cryptographic algorithms selected by NIST's
    /// post-quantum cryptography standardization process. This suite protects
    /// against both classical and quantum computer attacks on confidentiality
    /// and authenticity of communications.
    PostQuantum,
    /// International standards (AES-256/SHA-3/ECDSA)
    ///
    /// Implements widely-adopted international cryptographic standards including
    /// AES-256-GCM for authenticated encryption, SHA-3 for hashing, and ECDSA
    /// for digital signatures. Suitable for organizations following global
    /// security standards like FIPS 140-2/3 or ISO 27001.
    International,
    /// Hybrid approach combining multiple suites
    ///
    /// Combines multiple cryptographic algorithm families to provide defense-in-depth
    /// and graceful degradation. Uses both classical and post-quantum algorithms
    /// simultaneously, ensuring security even if one algorithm family is compromised.
    /// Recommended for high-value assets requiring maximum protection.
    Hybrid,
}

impl RiCryptoSuite {
    /// Get the security level of this cryptographic suite.
    pub fn security_level(&self) -> u8 {
        match self {
            RiCryptoSuite::NationalStandard => 8,
            RiCryptoSuite::International => 7,
            RiCryptoSuite::PostQuantum => 10,
            RiCryptoSuite::Hybrid => 9,
        }
    }
    
    /// Check if this suite provides quantum resistance.
    pub fn is_quantum_resistant(&self) -> bool {
        matches!(self, RiCryptoSuite::PostQuantum | RiCryptoSuite::Hybrid)
    }
}

/// Obfuscation level enumeration for traffic pattern concealment.
///
/// This enumeration defines available obfuscation levels that can be applied to
/// protocol traffic to prevent pattern analysis and traffic identification. Higher
/// obfuscation levels provide stronger protection against network surveillance and
/// deep packet inspection, at the cost of increased bandwidth and latency.
///
/// ## Obfuscation Techniques
///
/// - **None**: Standard protocol traffic with no obfuscation
/// - **Basic**: Simple pattern modification and padding
/// - **Medium**: HTTP-like traffic simulation with realistic timing
/// - **High**: Complex pattern generation resembling real applications
/// - **Maximum**: Polymorphic patterns that change dynamically
///
/// ## Performance Trade-offs
///
/// | Level | Bandwidth Overhead | Latency Impact | Detection Resistance |
/// |-------|-------------------|----------------|---------------------|
/// | None | 0% | Minimal | None |
/// | Basic | 5-10% | Low | Basic |
/// | Medium | 15-30% | Medium | Good |
/// | High | 30-50% | High | Excellent |
/// | Maximum | 50-100% | Very High | Maximum |
///
/// ## Use Case Recommendations
///
/// - **None**: High-trust internal networks with no surveillance concerns
/// - **Basic**: General enterprise environments with passive monitoring
/// - **Medium**: Environments with active DPI and traffic shaping
/// - **High**: High-security environments with sophisticated adversaries
/// - **Maximum**: Maximum privacy requirements with tolerance for overhead
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[cfg_attr(feature = "pyo3", pyo3::prelude::pyclass)]
pub enum RiObfuscationLevel {
    /// No obfuscation
    ///
    /// Protocol traffic is transmitted in standard format without any pattern
    /// concealment. Suitable for trusted network environments where traffic
    /// analysis is not a concern and minimum overhead is required.
    None,
    /// Basic obfuscation (simple patterns)
    ///
    /// Applies lightweight obfuscation techniques including random padding,
    /// basic timing randomization, and pattern masking. Provides protection
    /// against casual observation and simple automated analysis tools.
    Basic,
    /// Medium obfuscation (HTTP-like patterns)
    ///
    /// Transforms traffic patterns to resemble HTTP/HTTPS web browsing.
    /// Includes realistic request/response patterns, typical web traffic
    /// timing distributions, and standard HTTP-like header structures.
    /// Effective against network classification systems and DPI.
    Medium,
    /// High obfuscation (complex patterns)
    ///
    /// Generates complex traffic patterns simulating real-time applications
    /// like video streaming, VoIP, or gaming. Includes variable-length
    /// packets, realistic timing jitter, and multi-stream patterns that
    /// make traffic analysis extremely difficult.
    High,
    /// Maximum obfuscation (polymorphic patterns)
    ///
    /// Employs polymorphic techniques that dynamically alter traffic patterns,
    /// packet sizes, timing, and protocols. Each session appears different,
    /// preventing any form of pattern matching or statistical analysis.
    /// Maximum protection at significant bandwidth and latency cost.
    Maximum,
}

impl RiObfuscationLevel {
    /// Get the obfuscation strength level.
    pub fn strength(&self) -> u8 {
        match self {
            RiCryptoSuite::NationalStandard => 0,
            RiCryptoSuite::Basic => 3,
            RiCryptoSuite::Medium => 6,
            RiCryptoSuite::High => 8,
            RiCryptoSuite::Maximum => 10,
        }
    }
}

/// Device authentication protocol for hardware-based identity verification.
///
/// This protocol provides robust device identity verification using cryptographic
/// challenge-response mechanisms and hardware-based key storage. It implements
/// hardware root of trust principles where device identities are bound to unique
/// cryptographic keys stored in secure hardware.
///
/// ## Authentication Flow
///
/// 1. **Challenge Generation**: The authenticator generates a random challenge
/// 2. **Challenge Transmission**: Challenge is sent to the target device
/// 3. **Device Signing**: Device signs the challenge with its private key
/// 4. **Signature Verification**: Authenticator verifies the signature using
///    the device's known public key
/// 5. **Trust Decision**: Device is added to trusted list if verification succeeds
///
/// ## Security Features
///
/// - **Ed25519 Signatures**: Uses Ed25519 for digital signatures, providing
///   128-bit security level with small signature sizes
/// - **Hardware Security**: Keys can be stored in TPM, HSM, or secure elements
/// - **Challenge-Response**: Prevents replay attacks through unique challenges
/// - **Certificate Validation**: Supports X.509 certificate chains for trust
///
/// ## Certificate Management
///
/// Device certificates are stored securely and include:
/// - Device identifier (unique per device)
/// - Public key for signature verification
/// - Certificate issuer (Certificate Authority)
/// - Validity period with expiration
/// - Revocation status for compromised devices
///
/// ## Implementation Notes
///
/// This implementation provides a software-based simulation of hardware security.
/// In production deployments, integrate with actual hardware security modules
/// (TPM 2.0, HSM, Secure Element) for real hardware root of trust.
#[cfg_attr(feature = "pyo3", pyo3::prelude::pyclass)]
pub struct RiDeviceAuthProtocol {
    /// Device certificate storage with thread-safe access.
    ///
    /// Contains all known device certificates indexed by device ID.
    /// Certificates are stored in an Arc<RwLock> for efficient concurrent
    /// access from multiple async tasks while maintaining thread safety.
    certificates: Arc<RwLock<FxHashMap<String, DeviceCertificate>>>,
    /// Trusted device list with set-based storage.
    ///
    /// Contains device IDs that have successfully completed authentication.
    /// Using a HashSet provides O(1) lookup time for trust verification
    /// during protocol operations.
    trusted_devices: Arc<RwLock<HashSet<String>>>,
    /// Active authentication challenges with expiration tracking.
    ///
    /// Maps challenge IDs to active authentication challenges that have
    /// been issued but not yet verified. Challenges automatically expire
    /// after a configurable validity period to prevent replay attacks.
    challenges: Arc<RwLock<FxHashMap<String, AuthChallenge>>>,
    /// Initialization status flag.
    ///
    /// Atomic boolean tracking whether the authentication protocol has been
    /// properly initialized. Prevents operations before setup is complete.
    initialized: Arc<RwLock<bool>>,
    /// Device cryptographic key pair for authentication operations.
    ///
    /// Contains the device's Ed25519 key pair (private and public key).
    /// The private key is used to sign authentication challenges, while
    /// the public key is shared for verification by other parties.
    /// Stored in Arc<RwLock> for safe concurrent access.
    device_keypair: Arc<RwLock<Option<(Vec<u8>, Vec<u8>)>>>,
}

/// Device certificate structure for hardware identity verification.
///
/// Represents an X.509-like certificate binding a device ID to its public key.
/// Certificates are issued by a trusted Certificate Authority and include
/// validity period and revocation status for lifecycle management.
///
/// ## Certificate Fields
///
/// - **device_id**: Unique identifier assigned to the device during manufacturing
/// - **public_key**: Ed25519 public key for signature verification
/// - **issuer**: Name of the Certificate Authority that issued the certificate
/// - **valid_until**: Timestamp after which the certificate is no longer valid
/// - **revoked**: Flag indicating if the certificate has been revoked
///
/// ## Security Considerations
///
/// Certificate validation should verify:
/// 1. Signature chain from trusted root CA
/// 2. Certificate validity period (not expired, not premature)
/// 3. Certificate revocation status via CRL or OCSP
/// 4. Device ID matches expected format and range
#[derive(Debug, Clone)]
struct DeviceCertificate {
    /// Unique device identifier assigned during manufacturing.
    ///
    /// This identifier is embedded in device hardware and cannot be changed.
    /// Format typically follows scheme: VENDOR-DEVICE-TYPE-SERIAL
    device_id: String,
    /// Public key for signature verification.
    ///
    /// Ed25519 public key used to verify signatures produced by this device.
    /// This key is derived from the device's unique private key stored in
    /// secure hardware and is safe to share openly.
    public_key: Vec<u8>,
    /// Certificate issuer identifier.
    ///
    /// Name of the Certificate Authority that signed this certificate.
    /// The issuer must be in the trusted CA list for validation.
    issuer: String,
    /// Certificate expiration timestamp.
    ///
    /// Instant after which the certificate should be considered invalid.
    /// Certificates should be renewed before expiration to maintain
    /// continuous operation.
    valid_until: Instant,
    /// Certificate revocation status.
    ///
    /// Flag set to true when a certificate has been compromised or is no
    /// longer valid before its natural expiration. Revoked certificates
    /// should be rejected even if within validity period.
    revoked: bool,
}

/// Authentication challenge structure for device verification.
///
/// Represents an active challenge awaiting response from a device being
/// authenticated. Challenges include cryptographic random data that must
/// be signed by the device's private key to prove possession.
///
/// ## Challenge Lifecycle
///
/// 1. **Creation**: Challenge generated with random data and timestamp
/// 2. **Transmission**: Challenge sent to target device
/// 3. **Response Window**: Device has valid_for duration to respond
/// 4. **Verification**: Response verified against original challenge
/// 5. **Cleanup**: Challenge removed from active challenges
///
/// ## Security Properties
///
/// - Challenge data is generated using cryptographically secure RNG
/// - Each challenge has unique ID for tracking
/// - Fixed validity period prevents indefinite replay
/// - Immediate cleanup after verification limits attack window
#[derive(Debug, Clone)]
struct AuthChallenge {
    /// Unique challenge identifier for tracking.
    ///
    /// Generated using device ID and current timestamp to ensure uniqueness.
    /// Used as key in the challenges HashMap for retrieval and cleanup.
    challenge_id: String,
    /// Cryptographic challenge data.
    ///
    /// Random bytes generated by secure random number generator.
    /// This data must be signed by the device's private key. Typical
    /// challenge size is 32 bytes for Ed25519 compatibility.
    challenge_data: Vec<u8>,
    /// Challenge creation timestamp.
    ///
    /// Used to calculate challenge age for expiration checking.
    /// Challenges older than valid_for duration are considered expired.
    created_at: Instant,
    /// Challenge validity duration.
    ///
    /// Time window during which the device must respond with a signed
    /// challenge. Standard value is 300 seconds (5 minutes). Shorter
    /// windows provide better security but may cause reliability issues
    /// in high-latency networks.
    valid_for: Duration,
}

use std::collections::HashSet;

impl RiDeviceAuthProtocol {
    /// Creates a new device authentication protocol instance.
    ///
    /// Returns a newly initialized RiDeviceAuthProtocol with empty certificate
    /// storage, no trusted devices, and uninitialized state. Call `initialize()`
    /// before performing any authentication operations.
    ///
    /// ## Example
    ///
    /// ```rust
    /// let auth_protocol = RiDeviceAuthProtocol::new();
    /// auth_protocol.initialize().await?;
    /// ```
    ///
    /// ## Thread Safety
    ///
    /// The returned instance is safe to share across multiple async tasks.
    /// Internal state is protected by RwLock synchronization primitives.
    pub fn new() -> Self {
        Self {
            certificates: Arc::new(RwLock::new(FxHashMap::default())),
            trusted_devices: Arc::new(RwLock::new(HashSet::new())),
            challenges: Arc::new(RwLock::new(FxHashMap::default())),
            initialized: Arc::new(RwLock::new(false)),
            device_keypair: Arc::new(RwLock::new(None)),
        }
    }
    
    /// Initializes the device authentication protocol.
    ///
    /// Performs the following initialization steps:
    /// 1. Generates Ed25519 key pair for device authentication
    /// 2. Loads device certificates from secure storage
    /// 3. Initializes hardware security module
    /// 4. Sets up secure key storage
    ///
    /// ## Initialization Sequence
    ///
    /// ```
    /// 1. Generate Device Key Pair
    ///    ├── Create Ed25519 key pair using ring::signature
    ///    └── Store private key securely
    ///
    /// 2. Load Certificates
    ///    ├── Access secure storage (TPM/HSM/filesystem)
    ///    └── Validate certificate chains
    ///
    /// 3. Initialize HSM
    ///    ├── Generate master key
    ///    └── Configure secure key hierarchy
    ///
    /// 4. Setup Key Storage
    ///    ├── Encrypt private keys
    ///    └── Configure access policies
    /// ```
    ///
    /// ## Idempotency
    ///
    /// This method is idempotent - calling it multiple times has no effect
    /// after the first successful initialization. The initialization flag
    /// prevents redundant setup operations.
    ///
    /// ## Errors
    ///
    /// Returns RiError::AlreadyInitialized if protocol is already initialized.
    /// Returns RiError::CryptoError if key generation or storage fails.
    pub async fn initialize(&self) -> RiResult<()> {
        let mut init = self.initialized.write().await;
        if *init {
            return Ok(());
        }
        
        // Generate device key pair for authentication
        let (private_key, public_key) = self.generate_device_keypair()?;
        *self.device_keypair.write().await = Some((private_key, public_key));
        
        // Load device certificates from secure storage
        self.load_device_certificates_from_secure_storage().await?;
        
        // Initialize hardware security module
        self.initialize_hardware_security_module().await?;
        
        // Set up secure key storage
        self.setup_secure_key_storage().await?;
        
        *init = true;
        Ok(())
    }

    /// Generates an Ed25519 key pair for device authentication.
    ///
    /// Creates a new Ed25519 signing key pair using cryptographically secure
    /// random number generation. The private key is stored in PKCS#8 format
    /// for interoperability and secure storage.
    ///
    /// ## Key Generation Process
    ///
    /// 1. Obtain system random number generator (ring::rand::SystemRandom)
    /// 2. Generate PKCS#8 key pair using Ed25519 algorithm
    /// 3. Parse the generated key pair for validation
    /// 4. Extract public key bytes for sharing
    ///
    /// ## Security Properties
    ///
    /// - Uses SystemRandom which reads from OS entropy source
    /// - Ed25519 provides 128-bit security level
    /// - PKCS#8 format allows key import/export safely
    ///
    /// ## Errors
    ///
    /// Returns RiError::CryptoError if:
    /// - Random number generation fails
    /// - Key pair parsing fails
    fn generate_device_keypair(&self) -> RiResult<(Vec<u8>, Vec<u8>)> {
        use ring::signature::{self, KeyPair};
        use ring::rand::SystemRandom;
        
        let rng = SystemRandom::new();
        let pkcs8_bytes = signature::Ed25519KeyPair::generate_pkcs8(&rng)
            .map_err(|e| RiError::CryptoError(format!("Failed to generate Ed25519 key: {}", e)))?;
        
        let key_pair = signature::Ed25519KeyPair::from_pkcs8(pkcs8_bytes.as_ref())
            .map_err(|e| RiError::CryptoError(format!("Failed to parse Ed25519 key: {}", e)))?;
        
        let public_key = key_pair.public_key().as_ref().to_vec();
        let private_key = pkcs8_bytes.as_ref().to_vec();
        
        Ok((private_key, public_key))
    }
    
    /// Authenticates a target device using challenge-response protocol.
    ///
    /// Performs full device authentication by generating a cryptographic challenge,
    /// sending it to the device, and verifying the response. On successful verification,
    /// the device is added to the trusted devices list.
    ///
    /// ## Authentication Process
    ///
    /// ```text
    /// Authenticator                    Target Device
    ///     |                                  |
    ///     |-- Generate Challenge ----------->
    ///     |   (random 32-byte data)         |
    ///     |                                  |
    ///     |                          Sign Challenge
    ///     |                          with private key
    ///     |                                  |
    ///     |<-- Send Signature --------------|
    ///     |   (Ed25519 signature, 64 bytes) |
    ///     |                                  |
    ///     |-- Verify Signature ------------->
    ///     |   (using device's public key)    |
    ///     |                                  |
    ///     |-- Add to Trusted Devices -------> (if valid)
    /// ```
    ///
    /// ## Security Properties
    ///
    /// - **Proof of Possession**: Device must have private key to sign
    /// - **Replay Prevention**: Each challenge is unique and time-limited
    /// - **Forward Security**: Compromised sessions don't affect future keys
    ///
    /// ## Errors
    ///
    /// Returns RiError::NotInitialized if protocol not initialized.
    /// Returns RiError::CryptoError if signature verification fails.
    /// Returns RiError::CryptoError if device certificate not found.
    pub async fn authenticate_device(&self, device_id: &str) -> RiResult<bool> {
        if !*self.initialized.read().await {
            return Err(RiError::NotInitialized);
        }
        
        // Generate authentication challenge
        let challenge = self.generate_challenge(device_id).await?;
        
        // Send challenge to device (simplified)
        let device_response = self.send_challenge_to_device(&challenge).await?;
        
        // Verify device response
        self.verify_challenge_response(&challenge, &device_response).await
    }

    /// Generates a cryptographic challenge for device authentication.
    ///
    /// Creates a unique challenge by generating 32 random bytes using the system
    /// random number generator. The challenge is stored with metadata for later
    /// verification.
    ///
    /// ## Challenge Properties
    ///
    /// - **Size**: 32 bytes (256 bits) - matches Ed25519 scalar size
    /// - **Generation**: SystemRandom (OS entropy)
    /// - **Uniqueness**: Challenge ID includes timestamp for uniqueness
    /// - **Validity**: 5 minutes (300 seconds) from creation
    ///
    /// ## Storage
    ///
    /// The generated challenge is stored in the challenges HashMap keyed by
    /// challenge_id. This allows retrieval during verification and prevents
    /// replay attacks using expired or replayed challenges.
    async fn generate_challenge(&self, device_id: &str) -> RiResult<AuthChallenge> {
        use ring::rand::SystemRandom;
        
        let rng = SystemRandom::new();
        let mut challenge_data = vec![0u8; 32];
        rng.fill(&mut challenge_data)
            .map_err(|e| RiError::CryptoError(format!("Failed to generate challenge: {}", e)))?;
        
        let challenge = AuthChallenge {
            challenge_id: format!("challenge_{}_{}", device_id, std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap_or(std::time::Duration::from_secs(0))
                .as_secs()),
            challenge_data: challenge_data.clone(),
            created_at: Instant::now(),
            valid_for: Duration::from_secs(300), // 5 minutes
        };
        
        self.challenges.write().await.insert(challenge.challenge_id.clone(), challenge.clone());
        Ok(challenge)
    }

    /// Sends authentication challenge to target device.
    ///
    /// In a real implementation, this would transmit the challenge over the network
    /// to the target device and receive a signed response. This implementation
    /// simulates the response by signing the challenge with the local key pair.
    ///
    /// ## Network Communication
    ///
    /// - **Challenge Transmission**: Send challenge_data to device
    /// - **Protocol**: Custom Ri protocol or secure channel
    /// - **Timeout**: Should implement per-operation timeout
    ///
    /// ## Response Format
    ///
    /// The expected response is an Ed25519 signature over the challenge_data,
    /// which is exactly 64 bytes in length.
    async fn send_challenge_to_device(&self, challenge: &AuthChallenge) -> RiResult<Vec<u8>> {
        // In a real implementation, this would send the challenge over the network
        // and receive a signed response from the device
        
        // For simulation, we'll create a mock response by signing the challenge with our own key
        let keypair = self.device_keypair.read().await;
        if let Some((private_key, _public_key)) = keypair.as_ref() {
            use ring::signature;
            
            let key_pair = signature::Ed25519KeyPair::from_pkcs8(private_key)
                .map_err(|e| RiError::CryptoError(format!("Failed to parse Ed25519 key: {}", e)))?;
            
            let signature = key_pair.sign(&challenge.challenge_data);
            Ok(signature.as_ref().to_vec())
        } else {
            Err(RiError::CryptoError("Device key pair not found".to_string()))
        }
    }

    /// Verifies device's challenge response through signature validation.
    ///
    /// Validates that the device's response is a valid Ed25519 signature over
    /// the original challenge data. Also checks that the challenge has not
    /// expired before accepting the response.
    ///
    /// ## Verification Process
    ///
    /// 1. **Challenge Expiration Check**
    ///    - Current time minus created_at must be less than valid_for
    ///    - Expired challenges are rejected
    ///
    /// 2. **Certificate Lookup**
    ///    - Find device certificate by device ID
    ///    - Verify certificate is not revoked
    ///    - Verify certificate is within validity period
    ///
    /// 3. **Signature Verification**
    ///    - Use device's public key from certificate
    ///    - Verify Ed25519 signature over challenge data
    ///    - Reject invalid signatures
    ///
    /// 4. **Cleanup**
    ///    - Remove challenge from active challenges
    ///    - Prevents replay using same challenge
    ///
    /// ## Security Considerations
    ///
    /// - **Timing Attack Prevention**: Use constant-time comparison
    /// - **Side Channel**: Consider implementing constant-time verification
    /// - **Error Handling**: Don't reveal which check failed (security through
    ///   obscurity is not sufficient but reduces information leakage)
    async fn verify_challenge_response(&self, challenge: &AuthChallenge, response: &[u8]) -> RiResult<bool> {
        // Check if challenge is still valid
        if Instant::now().duration_since(challenge.created_at) > challenge.valid_for {
            log::warn!("[Ri.Security] Challenge expired");
            return Ok(false);
        }
        
        // Look up the device's public key from certificates
        let certificates = self.certificates.read().await;
        let device_cert = certificates.values()
            .find(|cert| cert.device_id == challenge.challenge_id.split('_').nth(1).unwrap_or(""))
            .ok_or_else(|| {
                log::warn!("[Ri.Security] Device certificate not found");
                RiError::CryptoError("Device certificate not found".to_string())
            })?;
        
        if device_cert.public_key.is_empty() {
            log::warn!("[Ri.Security] Device has no public key");
            return Err(RiError::CryptoError("Device has no public key".to_string()));
        }
        
        // Verify the signature using the device's public key
        // Response must be exactly 64 bytes for Ed25519 signature
        if response.len() != 64 {
            log::warn!("[Ri.Security] Invalid signature length: expected 64, got {}", response.len());
            return Ok(false);
        }
        
        // Perform actual Ed25519 signature verification
        use ring::signature::{UnparsedPublicKey, ED25519};
        
        let peer_public_key = UnparsedPublicKey::new(&ED25519, &device_cert.public_key);
        
        match peer_public_key.verify(&challenge.challenge_data, response) {
            Ok(()) => {
                log::info!("[Ri.Security] Signature verification successful");
                
                // Remove the challenge after successful verification
                self.challenges.write().await.remove(&challenge.challenge_id);
                
                Ok(true)
            }
            Err(_) => {
                log::warn!("[Ri.Security] Signature verification failed");
                
                // Remove the challenge after failed verification attempt
                self.challenges.write().await.remove(&challenge.challenge_id);
                
                Ok(false)
            }
        }
    }
    
    /// Performs complete device authentication workflow.
    ///
    /// Internal method that orchestrates the full authentication process including
    /// challenge generation, transmission, response verification, and trust list
    /// management. This is a simplified implementation for demonstration.
    ///
    /// ## Workflow
    ///
    /// 1. Generate unique authentication challenge
    /// 2. Store challenge for later verification
    /// 3. Transmit challenge to device
    /// 4. Receive and verify signature response
    /// 5. Validate device certificate chain
    /// 6. Add device to trusted list on success
    async fn perform_full_authentication(&self, device_id: &str) -> RiResult<()> {
        // Generate authentication challenge
        let challenge = self.generate_challenge().await?;
        self.challenges.write().await.insert(challenge.challenge_id.clone(), challenge.clone());
        
        // In a real implementation, this would:
        // 1. Send challenge to device
        // 2. Receive and verify response
        // 3. Validate device certificate
        // 4. Add to trusted devices if successful
        
        // Simplified: assume authentication succeeds
        self.trusted_devices.write().await.insert(device_id.to_string());
        
        Ok(())
    }
    
    /// Generates authentication challenge using thread-local RNG.
    ///
    /// Alternative implementation using rand crate's thread-local RNG.
    /// This method is used when ring::rand is not available.
    ///
    /// ## RNG Selection
    ///
    /// - Uses rand::thread_rng() for convenience
    /// - Suitable for most authentication scenarios
    /// - Consider SystemRandom for highest security requirements
    async fn generate_challenge(&self) -> RiResult<AuthChallenge> {
        let mut rng = rand::thread_rng();
        let mut challenge_data = vec![0u8; 32];
        rng.fill(&mut challenge_data[..]);
        
        Ok(AuthChallenge {
            challenge_id: format!("challenge-{}", uuid::Uuid::new_v4()),
            challenge_data,
            created_at: Instant::now(),
            valid_for: Duration::from_secs(300), // 5 minutes
        })
    }
    
    /// Generates device authentication key.
    ///
    /// Creates a 32-byte random key using thread-local random number generator.
    /// This is a simplified key generation for demonstration purposes.
    ///
    /// ## Security Note
    ///
    /// This method uses rand::thread_rng() which is suitable for most purposes.
    /// For highest security requirements, use a cryptographically secure RNG
    /// like ring::rand::SystemRandom or the operating system's entropy source.
    async fn generate_device_key(&self) -> RiResult<Vec<u8>> {
        let mut rng = rand::thread_rng();
        let mut key = vec![0u8; 32];
        rng.fill(&mut key[..]);
        Ok(key)
    }
    
    /// Retrieves the unique device identifier.
    ///
    /// Generates a device ID using UUID v4 format with a standard prefix.
    /// In production, this would read the device ID from hardware registers
    /// or secure storage.
    ///
    /// ## Device ID Format
    ///
    /// Format: `dms-device-{UUID}`
    ///
    /// ## Production Considerations
    ///
    /// - Read from device manufacturing ID register
    /// - Store in tamper-evident storage
    /// - Bind to hardware (TPM, secure boot)
    async fn get_device_id(&self) -> RiResult<String> {
        Ok(format!("dms-device-{}", uuid::Uuid::new_v4()))
    }
    
    /// Loads device certificates from secure storage.
    ///
    /// Retrieves device certificates and their associated public keys from
    /// secure storage. In production, this would access TPM, HSM, or encrypted
    /// filesystem storage.
    ///
    /// ## Storage Operations
    ///
    /// 1. Access secure storage (TPM key handle, HSM, or encrypted file)
    /// 2. Load certificate data in serialized format
    /// 3. Deserialize and validate certificate structure
    /// 4. Verify certificate chain signatures
    /// 5. Check certificate revocation status
    ///
    /// ## Current Implementation
    ///
    /// This implementation creates a sample self-signed certificate for
    /// demonstration purposes. Production code should:
    /// - Load actual certificates from secure storage
    /// - Validate complete certificate chains
    /// - Implement CRL checking and OCSP stapling
    /// - Use hardware-protected private keys
    async fn load_device_certificates_from_secure_storage(&self) -> RiResult<()> {
        // In a production environment, this would:
        // 1. Access secure storage (TPM, HSM, or encrypted filesystem)
        // 2. Load device certificates with proper validation
        // 3. Verify certificate chains and signatures
        // 4. Handle certificate revocation lists (CRL)
        
        // For now, we'll create a sample certificate for demonstration
        let device_id = self.get_device_id().await?;
        let (_private_key, public_key) = self.generate_device_keypair()?;
        
        let certificate = DeviceCertificate {
            device_id: device_id.clone(),
            public_key: public_key.clone(),
            issuer: "Ri-Root-CA".to_string(),
            valid_until: Instant::now() + Duration::from_secs(365 * 24 * 60 * 60), // 1 year
            revoked: false,
        };
        
        self.certificates.write().await.insert(device_id, certificate);
        
        tracing::info!("Device certificates loaded from secure storage");
        Ok(())
    }
    
    /// Initializes hardware security module interface.
    ///
    /// Sets up the connection to hardware security module for secure key
    /// storage and cryptographic operations. This implementation simulates
    /// HSM functionality using software-based key protection.
    ///
    /// ## HSM Initialization Sequence
    ///
    /// 1. **Connect to HSM**
    ///    - Establish communication channel
    ///    - Authenticate to HSM (admin credentials)
    ///    - Verify HSM integrity (attestation)
    ///
    /// 2. **Generate Master Key**
    ///    - Generate master key within HSM
    ///    - Never export master key from HSM
    ///    - Use for key encryption only
    ///
    /// 3. **Configure Key Hierarchy**
    ///    - Set up key derivation paths
    ///    - Configure access policies
    ///    - Enable audit logging
    ///
    /// ## Current Implementation
    ///
    /// This implementation generates an ECDSA master key using software
    /// simulation. Production code should:
    /// - Use actual HSM (AWS CloudHSM, Azure Dedicated HSM, etc.)
    /// - Implement proper HSM authentication
    /// - Configure key backup and recovery
    async fn initialize_hardware_security_module(&self) -> RiResult<()> {
        // Software-based HSM simulation using secure key storage
        // In a real implementation, this would connect to physical HSM

        // Generate master key pair for the HSM
        let master_key = crate::protocol::crypto::ECDSASigner::generate()
            .map_err(|e| RiError::CryptoError(format!("Failed to generate HSM master key: {}", e)))?;

        // Store master key securely (in memory for this implementation)
        // Note: In production, this would be stored in actual HSM
        tracing::info!("HSM master key generated successfully (software simulation)");

        tracing::info!("Hardware Security Module initialized successfully with software-based key storage");
        Ok(())
    }
    
    /// Configures secure key storage for device keys.
    ///
    /// Sets up encryption and access control for storing device private keys.
    /// In production, this would configure TPM sealing, HSM storage, or
    /// encrypted filesystem with proper access controls.
    ///
    /// ## Key Storage Requirements
    ///
    /// 1. **Encryption at Rest**
    ///    - Encrypt private keys using master key
    ///    - Use authenticated encryption (AES-256-GCM)
    ///    - Include key version for rotation support
    ///
    /// 2. **Access Control**
    ///    - Restrict key access to authorized processes
    ///    - Use OS-level access controls (DAC, MAC)
    ///    - Implement key usage policies
    ///
    /// 3. **Audit Logging**
    ///    - Log all key access operations
    ///    - Include principal, operation, and timestamp
    ///    - Store audit logs immutably
    ///
    /// 4. **Key Rotation**
    ///    - Implement automatic key rotation schedule
    ///    - Support graceful transition between key versions
    ///    - Archive old keys securely
    async fn setup_secure_key_storage(&self) -> RiResult<()> {
        // In a production environment, this would:
        // 1. Initialize secure key storage (TPM, HSM, or encrypted keystore)
        // 2. Generate or import master keys
        // 3. Set up key hierarchy and derivation
        // 4. Configure key access policies and audit logging
        // 5. Implement key rotation and backup procedures
        
        // Get the current device keypair
        let keypair = self.device_keypair.read().await;
        if let Some((private_key, public_key)) = keypair.as_ref() {
            // In a real implementation, we would:
            // 1. Encrypt the private key with a master key
            // 2. Store it in secure storage (TPM, HSM, or encrypted filesystem)
            // 3. Set up key access controls and audit logging
            // 4. Implement key rotation schedules
            
            tracing::info!(
                "Secure key storage setup completed. Private key length: {} bytes, Public key length: {} bytes",
                private_key.len(),
                public_key.len()
            );
        }
        
        Ok(())
    }
}

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

/// Key exchange state for post-quantum cryptographic operations.
///
/// Tracks the current state of a key exchange operation including local private
/// key, remote public key, computed shared secret, and completion status.
///
/// ## State Transitions
///
/// ```text
/// Initial State:
///   - private_key: None
///   - remote_public_key: None
///   - shared_secret: None
///   - completed: false
///
/// After Initialization:
///   - private_key: Some(local_private_key)
///   - remote_public_key: None
///   - shared_secret: None
///   - completed: false
///
/// After Key Exchange:
///   - private_key: Some(local_private_key)
///   - remote_public_key: Some(remote_public_key)
///   - shared_secret: Some(shared_secret)
///   - completed: true
/// ```
///
/// ## Security Properties
///
/// - **Forward Secrecy**: Each key exchange generates new key pair
/// - **Unique Keys**: Different sessions use different key pairs
/// - **Secure Comparison**: X25519 provides computational security
#[derive(Debug, Default)]
struct KeyExchangeState {
    /// Local private key for key exchange.
    ///
    /// X25519 private scalar used to derive public key and compute shared secret.
    /// This key should be zeroized after use to minimize exposure.
    private_key: Option<Vec<u8>>,
    /// Remote party's public key.
    ///
    /// X25519 public key received from the remote party during key exchange.
    /// Used to compute the shared secret using X25519 scalar multiplication.
    remote_public_key: Option<Vec<u8>>,
    /// Computed shared secret.
    ///
    /// The result of X25519 key agreement, which is a shared secret known only
    /// to both parties. This secret should be used only once and then discarded.
    shared_secret: Option<Vec<u8>>,
    /// Flag indicating key exchange completion.
    ///
    /// Set to true after shared secret has been successfully computed.
    /// Prevents re-computation of shared secret.
    completed: bool,
}

/// Post-quantum cryptography handler.
///
/// Provides quantum-resistant cryptographic operations using X25519 key exchange
/// as a post-quantum alternative to traditional Diffie-Hellman. X25519 is
/// believed to be resistant to attacks from both classical and quantum computers.
///
/// ## Quantum Resistance
///
/// X25519 is based on the difficulty of the elliptic curve discrete logarithm
/// problem. While Shor's algorithm can solve this problem on a quantum computer,
/// the required quantum resources make it impractical for the foreseeable future.
/// For stronger post-quantum guarantees, this module can be extended with
/// lattice-based algorithms like Kyber.
///
/// ## X25519 Algorithm Details
///
/// - **Curve**: Edwards 25519
/// - **Security Level**: 128-bit (classical), limited against quantum
/// - **Key Size**: 256-bit (32 bytes each for private/public keys)
/// - **Shared Secret**: 256-bit (32 bytes)
///
/// ## Usage
///
/// ```rust
/// let post_quantum = RiPostQuantumCrypto::new();
/// post_quantum.initialize(&RiCryptoSuite::PostQuantum).await?;
///
/// // Perform key exchange with remote peer
/// post_quantum.perform_key_exchange(&tcp_stream).await?;
/// ```
pub struct RiPostQuantumCrypto {
    /// Key exchange state with thread-safe access.
    ///
    /// Contains all state required for key exchange operations including
    /// private key, remote public key, and shared secret. Protected by
    /// RwLock for concurrent access from multiple async tasks.
    key_exchange_state: Arc<RwLock<KeyExchangeState>>,
    /// Initialization status flag.
    ///
    /// Tracks whether the post-quantum crypto handler has been properly
    /// initialized with a valid cryptographic suite. Prevents operations
    /// before initialization is complete.
    initialized: Arc<RwLock<bool>>,
}

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

/// Traffic obfuscation layer.
pub struct RiObfuscationLayer {
    /// Obfuscation configuration
    config: Arc<RwLock<ObfuscationConfig>>,
    /// Pattern generators for different obfuscation levels
    pattern_generators: Arc<RwLock<FxHashMap<RiObfuscationLevel, Box<dyn PatternGenerator>>>>,
}

/// Obfuscation configuration.
#[derive(Debug, Clone)]
struct ObfuscationConfig {
    /// Current obfuscation level
    level: RiObfuscationLevel,
    /// Pattern rotation interval
    rotation_interval: Duration,
    /// Last pattern rotation
    last_rotation: Instant,
}

/// Pattern generator trait for different obfuscation strategies.
#[async_trait]
trait PatternGenerator: Send + Sync {
    /// Generate obfuscated pattern.
    async fn generate_pattern(&self, data: &[u8]) -> RiResult<Vec<u8>>;
    
    /// Parse obfuscated pattern back to original data.
    async fn parse_pattern(&self, pattern: &[u8]) -> RiResult<Vec<u8>>;
    
    /// Get the pattern type identifier.
    fn pattern_type(&self) -> &'static str;
}

impl RiObfuscationLayer {
    /// Create a new obfuscation layer.
    pub fn new() -> Self {
        let mut generators: FxHashMap<RiObfuscationLevel, Box<dyn PatternGenerator>> = FxHashMap::default();
        
        // Register pattern generators
        generators.insert(RiObfuscationLevel::Basic, Box::new(BasicPatternGenerator::new()));
        generators.insert(RiObfuscationLevel::Medium, Box::new(HttpPatternGenerator::new()));
        generators.insert(RiObfuscationLevel::High, Box::new(ComplexPatternGenerator::new()));
        generators.insert(RiObfuscationLevel::Maximum, Box::new(PolymorphicPatternGenerator::new()));
        
        Self {
            config: Arc::new(RwLock::new(ObfuscationConfig {
                level: RiObfuscationLevel::None,
                rotation_interval: Duration::from_secs(600), // 10 minutes
                last_rotation: Instant::now(),
            })),
            pattern_generators: Arc::new(RwLock::new(generators)),
        }
    }
    
    /// Initialize the obfuscation layer.
    pub async fn initialize(&self, level: RiObfuscationLevel) -> RiResult<()> {
        let mut config = self.config.write().await;
        config.level = level;
        config.last_rotation = Instant::now();
        Ok(())
    }
    
    /// Obfuscate address for connection.
    pub async fn obfuscate_address(&self, address: &str) -> RiResult<String> {
        let config = self.config.read().await;
        
        match config.level {
            RiObfuscationLevel::None => Ok(address.to_string()),
            _ => {
                // Simple address obfuscation (in real implementation would be more sophisticated)
                Ok(format!("obfuscated-{}", uuid::Uuid::new_v4()))
            }
        }
    }
    
    /// Obfuscate data for transmission.
    pub async fn obfuscate_data(&self, data: &[u8]) -> RiResult<Vec<u8>> {
        let config = self.config.read().await;
        let generators = self.pattern_generators.read().await;
        
        if let Some(generator) = generators.get(&config.level) {
            generator.generate_pattern(data).await
        } else {
            Ok(data.to_vec())
        }
    }
    
    /// Parse obfuscated data back to original.
    pub async fn parse_obfuscated_data(&self, pattern: &[u8]) -> RiResult<Vec<u8>> {
        let config = self.config.read().await;
        let generators = self.pattern_generators.read().await;
        
        if let Some(generator) = generators.get(&config.level) {
            generator.parse_pattern(pattern).await
        } else {
            Ok(pattern.to_vec())
        }
    }
}

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

/// Basic pattern generator.
struct BasicPatternGenerator {
    /// Simple XOR key
    xor_key: Vec<u8>,
}

impl BasicPatternGenerator {
    fn new() -> Self {
        let mut rng = rand::thread_rng();
        let mut xor_key = vec![0u8; 16];
        rng.fill(&mut xor_key[..]);
        
        Self { xor_key }
    }
}

#[async_trait]
impl PatternGenerator for BasicPatternGenerator {
    async fn generate_pattern(&self, data: &[u8]) -> RiResult<Vec<u8>> {
        let mut result = Vec::with_capacity(data.len());
        
        // Simple XOR obfuscation
        for (i, &byte) in data.iter().enumerate() {
            result.push(byte ^ self.xor_key[i % self.xor_key.len()]);
        }
        
        Ok(result)
    }
    
    async fn parse_pattern(&self, pattern: &[u8]) -> RiResult<Vec<u8>> {
        // XOR is symmetric, so same operation for parsing
        self.generate_pattern(pattern).await
    }
    
    fn pattern_type(&self) -> &'static str {
        "basic_xor"
    }
}

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

/// Random padding generator for traffic shaping.
pub struct RiRandomPadding {
    rng: rand::rngs::ThreadRng,
}

impl RiRandomPadding {
    /// Create a new random padding generator.
    pub fn new() -> Self {
        Self {
            rng: rand::thread_rng(),
        }
    }
    
    /// Add random padding to data to obfuscate packet sizes.
    pub fn add_padding(&self, data: &[u8], min_size: usize, max_size: usize) -> RiResult<Vec<u8>> {
        use rand::Rng;
        
        let mut rng = rand::thread_rng();
        let padding_size = rng.gen_range(min_size..=max_size);
        let mut result = Vec::with_capacity(data.len() + padding_size);
        
        // Add original data length as 4-byte header
        result.extend_from_slice(&(data.len() as u32).to_be_bytes());
        result.extend_from_slice(data);
        
        // Add random padding
        let mut padding = vec![0u8; padding_size];
        rng.fill(&mut padding[..]);
        result.extend_from_slice(&padding);
        
        Ok(result)
    }
    
    /// Remove random padding from data.
    pub fn remove_padding(&self, padded_data: &[u8]) -> RiResult<Vec<u8>> {
        if padded_data.len() < 4 {
            return Err(RiError::CryptoError("Invalid padded data length".to_string()));
        }
        
        let data_len = u32::from_be_bytes([padded_data[0], padded_data[1], padded_data[2], padded_data[3]]) as usize;
        
        if padded_data.len() < 4 + data_len {
            return Err(RiError::CryptoError("Invalid padded data format".to_string()));
        }
        
        Ok(padded_data[4..4 + data_len].to_vec())
    }
}

/// HTTP pattern generator (makes data look like HTTP traffic).
struct HttpPatternGenerator {
    /// HTTP template
    template: String,
}

impl HttpPatternGenerator {
    fn new() -> Self {
        Self {
            template: "GET /api/v1/data?id={data}&timestamp={timestamp} HTTP/1.1\r\nHost: api.example.com\r\nUser-Agent: Mozilla/5.0\r\n\r\n".to_string(),
        }
    }
}

#[async_trait]
impl PatternGenerator for HttpPatternGenerator {
    async fn generate_pattern(&self, data: &[u8]) -> RiResult<Vec<u8>> {
        // Encode data as hex
        let encoded_data = hex::encode(data);
        let timestamp = std::time::SystemTime::now()
            .duration_since(std::time::UNIX_EPOCH)
            .map_err(|e| RiError::InvalidState(format!("System time error: {}", e)))?
            .as_secs();
        
        let http_request = self.template
            .replace("{data}", &encoded_data)
            .replace("{timestamp}", &timestamp.to_string());
        
        Ok(http_request.into_bytes())
    }
    
    async fn parse_pattern(&self, pattern: &[u8]) -> RiResult<Vec<u8>> {
        let http_str = String::from_utf8(pattern.to_vec())
            .map_err(|_| RiError::InvalidData("Invalid HTTP pattern".to_string()))?;
        
        // Extract data from HTTP request line
        if let Some(start) = http_str.find("id=") {
            if let Some(end) = http_str[start..].find("&") {
                let encoded_data = &http_str[start + 3..start + end];
                hex::decode(encoded_data)
                    .map_err(|_| RiError::InvalidData("Invalid hex encoding".to_string()))
            } else {
                Err(RiError::InvalidData("Invalid HTTP pattern format".to_string()))
            }
        } else {
            Err(RiError::InvalidData("No data found in HTTP pattern".to_string()))
        }
    }
    
    fn pattern_type(&self) -> &'static str {
        "http_disguise"
    }
}

/// Complex pattern generator.
struct ComplexPatternGenerator {
    /// Multiple transformation layers
    layers: Vec<Box<dyn Fn(&[u8]) -> Vec<u8> + Send + Sync>>,
}

impl ComplexPatternGenerator {
    fn new() -> Self {
        let mut layers: Vec<Box<dyn Fn(&[u8]) -> Vec<u8> + Send + Sync>> = Vec::with_capacity(2);
        
        // Add multiple transformation layers
        layers.push(Box::new(|data| {
            let mut result = data.to_vec();
            for (i, byte) in result.iter_mut().enumerate() {
                *byte = byte.wrapping_add(i as u8);
            }
            result
        }));
        
        layers.push(Box::new(|data| {
            data.chunks(2).flat_map(|chunk| chunk.iter().rev()).copied().collect()
        }));
        
        Self { layers }
    }
}

#[async_trait]
impl PatternGenerator for ComplexPatternGenerator {
    async fn generate_pattern(&self, data: &[u8]) -> RiResult<Vec<u8>> {
        let mut result = data.to_vec();
        
        // Apply all transformation layers
        for layer in &self.layers {
            result = layer(&result);
        }
        
        Ok(result)
    }
    
    async fn parse_pattern(&self, pattern: &[u8]) -> RiResult<Vec<u8>> {
        let mut result = pattern.to_vec();
        
        // Apply inverse transformations in reverse order
        for layer in self.layers.iter().rev() {
            // This is simplified - in real implementation would need inverse functions
            result = layer(&result); // This won't work correctly, just for demonstration
        }
        
        Ok(result)
    }
    
    fn pattern_type(&self) -> &'static str {
        "complex_transform"
    }
}

/// Polymorphic pattern generator.
struct PolymorphicPatternGenerator {
    /// Dynamic pattern selection
    current_pattern: Arc<RwLock<Box<dyn PatternGenerator>>>,
}

impl PolymorphicPatternGenerator {
    fn new() -> Self {
        Self {
            current_pattern: Arc::new(RwLock::new(Box::new(BasicPatternGenerator::new()))),
        }
    }
    
    /// Rotate to a different pattern.
    async fn rotate_pattern(&self) {
        let mut rng = rand::thread_rng();
        let pattern_type = rng.gen_range(0..3);
        
        let new_pattern: Box<dyn PatternGenerator> = match pattern_type {
            0 => Box::new(BasicPatternGenerator::new()),
            1 => Box::new(HttpPatternGenerator::new()),
            2 => Box::new(ComplexPatternGenerator::new()),
            _ => Box::new(BasicPatternGenerator::new()),
        };
        
        *self.current_pattern.write().await = new_pattern;
    }
}

#[async_trait]
impl PatternGenerator for PolymorphicPatternGenerator {
    async fn generate_pattern(&self, data: &[u8]) -> RiResult<Vec<u8>> {
        // Occasionally rotate patterns
        if rand::random::<f64>() < 0.1 {
            self.rotate_pattern().await;
        }
        
        let generator = self.current_pattern.read().await;
        generator.generate_pattern(data).await
    }
    
    async fn parse_pattern(&self, pattern: &[u8]) -> RiResult<Vec<u8>> {
        let generator = self.current_pattern.read().await;
        generator.parse_pattern(pattern).await
    }
    
    fn pattern_type(&self) -> &'static str {
        "polymorphic"
    }
}