Crate isap_aead

Expand description

ISAP authenticated encryption with Keccak and Ascon permutations

This crate provides an implementation of the authenticated encryption scheme ISAP. As specified in ISAP version 2, implementations are provided for the Ascon and Keccak based instances.

Usage

Simple usage (allocating, no associated data):

use isap_aead::IsapAscon128; // Or `IsapAscon128A`, `IsapKeccak128`, `IsapKeccak128A`
use isap_aead::aead::{Aead, KeyInit};

let key = b"very secret key.";
let cipher = IsapAscon128::new(key.into());
let nonce = b"unique nonce 012"; // 128-bits; unique per message

let ciphertext = cipher.encrypt(nonce.into(), b"plaintext message".as_ref())
    .expect("encryption failure!"); // NOTE: handle this error to avoid panics!

let plaintext = cipher.decrypt(nonce.into(), ciphertext.as_ref())
    .expect("decryption failure!"); // NOTE: handle this error to avoid panics!

assert_eq!(&plaintext, b"plaintext message");

In-place Usage (eliminates `alloc` requirement)

Similar to other crates implementing aead interfaces, this crate also offers an optional alloc feature which can be disabled in e.g. microcontroller environments that don’t have a heap. See aead::AeadInPlace for more details.

use isap_aead::IsapAscon128; // Or `IsapAscon128A`, `IsapKeccak128`, `IsapKeccak128A`
use isap_aead::aead::{AeadInPlace, KeyInit};
use isap_aead::aead::heapless::Vec;

let key = b"very secret key.";
let cipher = IsapAscon128::new(key.into());
let nonce = b"unique nonce 012"; // 128-bits; unique per message

let mut buffer: Vec<u8, 128> = Vec::new(); // Buffer needs 16-bytes overhead for authentication tag
buffer.extend_from_slice(b"plaintext message");

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

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

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