Bouncy Castle for .NET is a comprehensive, production-grade cryptographic library providing implementations of a vast range of symmetric and asymmetric ciphers, hash functions, message authentication codes, digital signatures, key agreement protocols, key encapsulation mechanisms (including post-quantum schemes like ML-KEM, ML-DSA, SLH-DSA), secure random number generation (NIST SP 800-90A DRBG), and ASN.1 encoding/decoding (DER, BER, DL). It supports high-level protocol implementations for TLS/DTLS (client and server, including PSK, SRP, and post-quantum key exchange), OpenPGP (RFC 4880/9580), CMS (Cryptographic Message Syntax), CMP, CRMF, OCSP, TSP, and X.509 certificate generation and validation. The library is designed as a class library with a monolithic architecture organized into namespaces (Org.BouncyCastle.Crypto, .Asn1, .Tls, .Bcpg, .Cms, etc.), exposing both low-level primitives and high-level builders. It targets multiple .NET runtimes with conditional compilation for hardware intrinsics (AES-NI, PCLMULQDQ, SSE/AVX) and Span<T> support. The codebase is actively maintained, with ongoing migration from older algorithm names (e.g., Dilithium → ML-DSA) and extensive use of factory patterns and interface-based abstractions, making it a solid foundation for secure application development.
FairEmail is a fully-featured, open-source, privacy-oriented email client for Android. It supports IMAP, POP3, SMTP, OpenPGP, S/MIME, and OAuth for major providers (Gmail, Outlook, Yahoo). The app is built as a standard Android application with Activities, Fragments, Services, and WorkManager workers. It uses Room for local persistence, LiveData for reactive UI, and a custom async pattern (SimpleTask) for background operations. The codebase is notable for its extensive use of vendored libraries: it includes modified copies of JavaMail (javax.mail, com.sun.mail), AndroidX internals (Room, Paging, Emoji2, RecyclerView Selection), Google Protocol Buffers, and native language/encoding detection engines (CLD3, compact_enc_det). This hybrid approach provides deep email protocol support and privacy features like tracker blocking, certificate transparency, and DANE, but also introduces maintenance overhead and potential drift from upstream versions. The app integrates AI features (Gemini, OpenAI) for summarization and rule actions, and includes a full rule/filter engine. Despite the heavy vendoring, the core application code demonstrates solid engineering with clean abstractions, custom views that work around Android platform bugs, and a consistent async pattern. The repository is actively maintained with frequent releases and responsive issue triage.