Pure Rust key-exchange implementations for the OxiCrypto stack.

Provides a [KeyAgreement]-trait wrapper for X25519 Diffie-Hellman, X448 Diffie-Hellman, ECDH over NIST P-256, P-384, and P-521, plus key generation helpers.

Key generation

All generate_keypair functions accept any RNG implementing [rand_core::TryCryptoRng] (rand_core 0.10+).

Shared-secret rejection

Every agree() implementation rejects all-zero shared secrets via constant-time comparison. An all-zero output indicates a low-order (small subgroup) public key attack; callers will receive [CryptoError::Kex] in that case.