LibEmiddle v2.6.0

🎯 Overview

Production-readiness sprint delivering security hardening, encrypted persistence, structured error handling, and comprehensive test coverage across the full Signal Protocol stack.

---

✨ What's New

🔒 Security Hardening

• NEW: Group session replay attack protection — per-sender message ID tracking with 1,000-entry cap
• NEW: Chat session replay protection — 500-message sliding window FIFO ring buffer
• NEW: Post-removal forward secrecy — automatic chain key rotation when a group member is removed
• NEW: Encrypted device list persistence — AES-GCM authenticated storage with atomic writes

📡 API & Messaging

• NEW: StartListeningAsync() now auto-starts mailbox polling — no extra call needed
• NEW: O(1) message routing via SenderIdentityKey field on EncryptedMessage — replaces O(n) brute-force session scan
• NEW: CreateChatSessionAsync(byte[] identityKey) overload — cache-first, transport fallback
• NEW: SendToDeviceAsync(deviceId, message) — device-to-device encrypted message routing
• NEW: FetchRecipientKeyBundleAsync() — validates bundle signature before caching
• NEW: OPKManager one-time prekey consumption tracking with automatic replenishment

🗄️ Persistence & Lifecycle

• NEW: DeviceStorage — survives process restarts with encrypted device list files
• NEW: IAsyncDisposable on LibEmiddleClient — safe await using cleanup
• NEW: LibEmiddleException with typed LibEmiddleErrorCode — 12 structured error codes replacing generic exceptions

🧪 Testing

• NEW: Concurrency tests — 7 tests covering multi-thread encrypt/decrypt, session isolation, nonce uniqueness
• NEW: Stress tests — 10 sessions × 50 messages, 5 group sessions × 20 messages, error path coverage

---

⚠️ Important Changes

• Password KDF migrated from HKDF + fixed salt to Argon2id (64 MB, 2 passes) — stronger brute-force resistance
• SecureWebSocketClient now throws LibEmiddleException(TransportError) instead of bare Exception
• Fixed AES-GCM detached decryption P/Invoke signature (was silently failing all decryption)
• Fixed MessageSigning.VerifyObject<T>() reversed argument order (was failing all signature verification)

---

✅ Compatibility

Fully backward compatible with v2.5.1 — drop-in replacement, no code changes needed for existing integrations.

---

📊 Testing

• ✅ 532 tests passing (up from 388 baseline)
• ✅ No breaking changes
• ✅ No new failures

v2.5.1

LibEmiddle v2.5.1 - Documentation & Refactoring Release

🎯 Overview

Documentation and code quality release addressing user feedback about the mailbox transport system.

✨ What's New

📚 Comprehensive Documentation

• NEW: Mailbox Transport Guide - 500+ line complete guide
• NEW: Message Flow Diagrams - Visual Mermaid sequence diagrams
• Enhanced README with dedicated transport section and examples

🔧 Code Improvements

• Refactored polling logic, eliminated ~120 lines of duplicate code
• Created StartPollingLoopAsync() helper in BaseMailboxTransport
• Improved maintainability across transport implementations

⚠️ Important Clarifications

• WebRTC Transport: Clarified as stub only (not production-ready), planned for v3.0
• Updated all documentation to reflect accurate feature status

✅ Compatibility

Fully backward compatible with v2.5.0 - Drop-in replacement, no code changes needed!

📊 Testing

• ✅ All 275 tests passing (improved from 273 baseline)
• ✅ No breaking changes
• ✅ No new failures

v2.5.0

What's Changed

• Update CHANGELOG.md by @rbenzing in #1
• merge main to experimental by @rbenzing in #2
• Merge pull request #2 from rbenzing/main by @rbenzing in #3

New Contributors

• @rbenzing made their first contribution in #1

Full Changelog: v2.0.0...v2.5.0

v2.0.0

Full Changelog: https://github.com/rbenzing/LibEmiddle/commits/v2.0.0