Crate ccm Copy item path

§RustCrypto: CCM

Pure Rust implementation of the Counter with CBC-MAC (CCM) mode (RFC 3610): an Authenticated Encryption with Associated Data (AEAD) algorithm generic over block ciphers with block size equal to 128 bits.

For example, it can be combined with AES into the various parametrizations of AES-CCM.

Documentation

§Security Notes

No security audits of this crate have ever been performed, and it has not been thoroughly assessed to ensure its operation is constant-time on common CPU architectures.

USE AT YOUR OWN RISK!

§License

Licensed under either of:

• Apache License, Version 2.0
• MIT license

at your option.

§Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

§Usage

Simple usage (allocating, no associated data):

use aes::Aes256;
use ccm::{
    aead::{Aead, AeadCore, KeyInit, array::Array},
    consts::{U10, U13},
    Ccm,
};

// AES-256-CCM type with tag and nonce size equal to 10 and 13 bytes respectively
pub type Aes256Ccm = Ccm<Aes256, U10, U13>;

let key = Aes256Ccm::generate_key().expect("key generation failure");
let cipher = Aes256Ccm::new(&key);

let nonce = Aes256Ccm::generate_nonce().expect("nonce failure"); // MUST be unique per message
let ciphertext = cipher.encrypt(&nonce, b"plaintext message".as_ref())?;

let plaintext = cipher.decrypt(&nonce, ciphertext.as_ref())?;
assert_eq!(&plaintext, b"plaintext message");

§In-place Usage (eliminates alloc requirement)

This crate has an optional alloc feature which can be disabled in e.g. microcontroller environments that don’t have a heap.

The AeadInOut::encrypt_in_place and AeadInOut::decrypt_in_place methods accept any type that impls the aead::Buffer trait which contains the plaintext for encryption or ciphertext for decryption.

Enabling the arrayvec feature of this crate will provide an impl of aead::Buffer for arrayvec::ArrayVec (re-exported from the aead crate as [aead::arrayvec::ArrayVec]), and enabling the bytes feature of this crate will provide an impl of aead::Buffer for bytes::BytesMut (re-exported from the aead crate as [aead::bytes::BytesMut]).

It can then be passed as the buffer parameter to the in-place encrypt and decrypt methods:

use aes::Aes256;
use ccm::{
    aead::{AeadCore, AeadInOut, KeyInit, arrayvec::ArrayVec},
    consts::{U10, U13},
    Ccm,
};

// AES-256-CCM type with tag and nonce size equal to 10 and 13 bytes respectively
pub type Aes256Ccm = Ccm<Aes256, U10, U13>;

let key = Aes256Ccm::generate_key().expect("key generation failure");
let cipher = Aes256Ccm::new(&key);

let nonce = Aes256Ccm::generate_nonce().expect("nonce failure"); // MUST be unique per message
let mut buffer: ArrayVec<u8, 128> = ArrayVec::new(); // Note: buffer needs 16-bytes overhead for auth tag
buffer.try_extend_from_slice(b"plaintext message").unwrap();

// Encrypt `buffer` in-place, replacing the plaintext contents with ciphertext
cipher.encrypt_in_place(&nonce, b"", &mut buffer)?;

// `buffer` now contains the message ciphertext
assert_ne!(buffer.as_ref(), b"plaintext message");

// Decrypt `buffer` in-place, replacing its ciphertext context with the original plaintext
cipher.decrypt_in_place(&nonce, b"", &mut buffer)?;
assert_eq!(buffer.as_ref(), b"plaintext message");