dcrypt-kem 4.0.1

Key Encapsulation Mechanisms for the dcrypt library
Documentation 
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// File: crates/kem/src/ecdh/mod.rs
//! ECDH-KEM implementations for NIST curves
//!
//! This module provides ECDH-based KEMs using P-224, P-256, P-384,
//! P-521, and secp256k1. These are domain-separated dcrypt constructions,
//! not RFC 9180 HPKE suites.

use dcrypt_internal::zeroing::{boxed_bytes_zeroed, Zeroizing, ZeroizingBytes};

fn concat_kdf_ikm(shared: &[u8], ephemeral: &[u8], recipient: &[u8]) -> ZeroizingBytes {
    let len = shared
        .len()
        .checked_add(ephemeral.len())
        .and_then(|value| value.checked_add(recipient.len()))
        .expect("fixed-width ECDH KDF transcript length cannot overflow");
    let mut output = Zeroizing::new(boxed_bytes_zeroed(len));
    let ephemeral_start = shared.len();
    let recipient_start = ephemeral_start + ephemeral.len();
    output[..ephemeral_start].copy_from_slice(shared);
    output[ephemeral_start..recipient_start].copy_from_slice(ephemeral);
    output[recipient_start..].copy_from_slice(recipient);
    output
}

pub mod k256;
pub mod p224;
pub mod p256;
pub mod p384;
pub mod p521;

// Re-export the P-224 types
pub use p224::{
    EcdhP224, EcdhP224Ciphertext, EcdhP224PublicKey, EcdhP224SecretKey, EcdhP224SharedSecret,
};

// Re-export the P-256 types
pub use p256::{
    EcdhP256, EcdhP256Ciphertext, EcdhP256PublicKey, EcdhP256SecretKey, EcdhP256SharedSecret,
};

// Re-export the P-384 types
pub use p384::{
    EcdhP384, EcdhP384Ciphertext, EcdhP384PublicKey, EcdhP384SecretKey, EcdhP384SharedSecret,
};

// Re-export the P-521 types
pub use p521::{
    EcdhP521, EcdhP521Ciphertext, EcdhP521PublicKey, EcdhP521SecretKey, EcdhP521SharedSecret,
};

// Re-export the K-256 (secp256k1) types
pub use k256::{
    EcdhK256, EcdhK256Ciphertext, EcdhK256PublicKey, EcdhK256SecretKey, EcdhK256SharedSecret,
};