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#![no_std]
// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#![forbid(unsafe_code)]
#![deny(
missing_docs,
clippy::indexing_slicing,
clippy::unwrap_used,
clippy::panic,
clippy::expect_used
)]
//! Defining traits for an LDT specific Tweakable Block Cipher
/// `B` is the block size in bytes.
pub trait TweakableBlockCipher<const B: usize> {
/// The tweak type used with encryption/decryption.
type Tweak: From<[u8; B]>;
/// the tweakable block cipher key type for the tbc
type Key: TweakableBlockCipherKey;
/// Create a new tweakable block cipher for ldt from a tbc key
fn new(key: &Self::Key) -> Self;
/// Encrypt `block` in place using the specified `tweak`.
fn encrypt(&self, tweak: Self::Tweak, block: &mut [u8; B]);
/// Decrypt `block` in place using the specified `tweak`.
fn decrypt(&self, tweak: Self::Tweak, block: &mut [u8; B]);
}
/// A tweakable block cipher key as used by LDT
pub trait TweakableBlockCipherKey: Sized {
/// Two tweakable block cipher keys concatenated, as used by LDT
type ConcatenatedKeyArray: ConcatenatedKeyArray;
/// Split a concatenated array of two keys' bytes into individual keys.
fn split_from_concatenated(key: &Self::ConcatenatedKeyArray) -> (Self, Self);
/// Concatenate with another key to form an array of both key's bytes.
fn concatenate_with(&self, other: &Self) -> Self::ConcatenatedKeyArray;
}
/// The array form of two concatenated tweakable block cipher keys.
pub trait ConcatenatedKeyArray: Sized {
/// Build a concatenated key from a secure RNG.
fn from_random<R: rand::Rng + rand::CryptoRng>(rng: &mut R) -> Self;
}
impl ConcatenatedKeyArray for [u8; 64] {
fn from_random<R: rand::Rng + rand::CryptoRng>(rng: &mut R) -> Self {
let mut arr = [0; 64];
rng.fill(&mut arr);
arr
}
}
impl ConcatenatedKeyArray for [u8; 128] {
fn from_random<R: rand::Rng + rand::CryptoRng>(rng: &mut R) -> Self {
let mut arr = [0; 128];
rng.fill(&mut arr);
arr
}
}
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