dcrypt: A Modern, High-Assurance Cryptographic Library in Rust

The emergence of quantum computing threatens the security of widely deployed public-key cryptosystems, necessitating a transition to post-quantum cryptography (PQC). We present dcrypt, a comprehensive cryptographic library implemented entirely in safe Rust that provides both classical and NIST-standardized post-quantum algorithms alongside novel hybrid constructions. dcrypt is the first publicly released, production-ready implementation of the complete CRYSTALS-Dilithium / ML-DSA signature scheme in pure Rust with zero unsafe code, zero FFI dependencies, and full constant-time execution. It is also the first pure-Rust library to provide native hybrid key encapsulation mechanisms (ECDH + Kyber) and hybrid digital signatures (ECDSA + Dilithium) as composable cryptographic primitives. The library's architecture enforces memory safety through Rust's ownership model, eliminates entire classes of vulnerabilities common in C/C++ cryptographic implementations, and maintains constant-time execution verified through an integrated constant-time verification suite. Performance benchmarks demonstrate that pure-Rust post-quantum cryptography achieves production-grade speeds, with hybrid constructions introducing less than 10% overhead compared to post-quantum–only implementations. dcrypt provides a high-assurance foundation for quantum-resistant applications across embedded systems, enterprise infrastructure, and decentralized networks.