XTEA implementation (#422)

This PR implements XTEA as described by various sources, including
https://en.wikipedia.org/wiki/XTEA,

XTEA is a historical cipher, which is no longer commonly used today, but
some legacy software still uses it to this day.

I tested that the cipher methods get properly unrolled, which boosts a
3x speed increase, and is one of the faster ciphers in this collection.
(Hopefully there will be an unroll pragma sometime in the future)

Partially solves #1

I decided against pre-computing keys as the computation is trivial, and
doesn't have a noticeable impact on speed, probably because of memory
accesses and that 256 byte don't fit easily in a cache line anyway.

.github/workflows/xtea.yml

@@ -0,0 +1,60 @@
+name: xtea
+
+on:
+  pull_request:
+    paths:
+      - "xtea/**"
+      - "Cargo.*"
+  push:
+    branches: master
+
+defaults:
+  run:
+    working-directory: xtea
+
+env:
+  CARGO_INCREMENTAL: 0
+  RUSTFLAGS: "-Dwarnings"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust:
+          - 1.65.0 # MSRV
+          - stable
+        target:
+          - thumbv7em-none-eabi
+          - wasm32-unknown-unknown
+    steps:
+      - uses: actions/checkout@v3
+      - uses: RustCrypto/actions/cargo-cache@master
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+          targets: ${{ matrix.target }}
+      - run: cargo build --no-default-features --release --target ${{ matrix.target }}
+
+  minimal-versions:
+    uses: RustCrypto/actions/.github/workflows/minimal-versions.yml@master
+    with:
+        working-directory: ${{ github.workflow }}
+
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust:
+          - 1.65.0 # MSRV
+          - stable
+    steps:
+      - uses: actions/checkout@v3
+      - uses: RustCrypto/actions/cargo-cache@master
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+      - run: cargo check --all-features
+      - run: cargo test --no-default-features
+      - run: cargo test
+      - run: cargo test --all-features

Cargo.toml

@@ -9,6 +9,7 @@ members = [
     "cast5",
     "cast6",
     "des",
+    "gift",
     "idea",
     "kuznyechik",
     "magma",
@@ -19,7 +20,7 @@ members = [
     "speck",
     "twofish",
     "threefish",
-    "gift",
+    "xtea",
 ]
 
 [profile.dev]

README.md

@@ -54,6 +54,7 @@ It's generally recommended not to use other cipher implementations in this repos
 | [Speck] | [`speck-cipher`] | [![crates.io](https://img.shields.io/crates/v/speck-cipher.svg)](https://crates.io/crates/speck-cipher) | [![Documentation](https://docs.rs/speck-cipher/badge.svg)](https://docs.rs/speck-cipher) | ![MSRV 1.65][msrv-1.65] |
 | [Threefish] | [`threefish`] | [![crates.io](https://img.shields.io/crates/v/threefish.svg)](https://crates.io/crates/threefish) | [![Documentation](https://docs.rs/threefish/badge.svg)](https://docs.rs/threefish) | ![MSRV 1.65][msrv-1.65] |
 | [Twofish] | [`twofish`] | [![crates.io](https://img.shields.io/crates/v/twofish.svg)](https://crates.io/crates/twofish) | [![Documentation](https://docs.rs/twofish/badge.svg)](https://docs.rs/twofish) | ![MSRV 1.65][msrv-1.65] |
+| [XTEA] | [`xtea`] | [![crates.io](https://img.shields.io/crates/v/xtea.svg)](https://crates.io/crates/xtea) | [![Documentation](https://docs.rs/xtea/badge.svg)](https://docs.rs/xtea) | ![MSRV 1.65][msrv-1.65] |
 
 ### Minimum Supported Rust Version (MSRV) Policy
 
@@ -105,6 +106,7 @@ dual licensed as above, without any additional terms or conditions.
 [`speck-cipher`]: ./speck
 [`threefish`]: ./threefish
 [`twofish`]: ./twofish
+[`xtea`]: ./xtea
 
 [//]: # (links)
 
@@ -131,3 +133,4 @@ dual licensed as above, without any additional terms or conditions.
 [Speck]: https://en.wikipedia.org/wiki/Speck_(cipher)
 [Threefish]: https://en.wikipedia.org/wiki/Threefish
 [Twofish]: https://en.wikipedia.org/wiki/Twofish
+[XTEA]: https://en.wikipedia.org/wiki/XTEA

xtea/CHANGELOG.md

@@ -0,0 +1,9 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## 0.1.0 (2024-05-11)
+- Initial release

xtea/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "xtea"
+version = "0.1.0-pre"
+description = "XTEA block cipher"
+authors = ["RustCrypto Developers"]
+license = "MIT OR Apache-2.0"
+edition = "2021"
+rust-version = "1.65"
+readme = "README.md"
+documentation = "https://docs.rs/xtea"
+repository = "https://github.com/RustCrypto/block-ciphers"
+keywords = ["crypto", "xtea", "block-cipher"]
+categories = ["cryptography", "no-std"]
+
+[dependencies]
+cipher = "=0.5.0-pre.4"
+
+[dev-dependencies]
+cipher = { version = "=0.5.0-pre.4", features = ["dev"] }
+
+[features]
+zeroize = ["cipher/zeroize"]
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]

xtea/LICENSE-APACHE

@@ -0,0 +1,13 @@
+Copyright 2024 Kevin Ludwig
+
+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.

xtea/LICENSE-MIT

@@ -0,0 +1,25 @@
+Copyright (c) 2024 Kevin Ludwig
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.

xtea/README.md

@@ -0,0 +1,71 @@
+# RustCrypto: XTEA Cipher
+
+[![crate][crate-image]][crate-link]
+[![Docs][docs-image]][docs-link]
+![Apache2/MIT licensed][license-image]
+![Rust Version][rustc-image]
+[![Project Chat][chat-image]][chat-link]
+[![Build Status][build-image]][build-link]
+[![HAZMAT][hazmat-image]][hazmat-link]
+
+Pure Rust implementation of the [XTEA block cipher][1].
+
+[Documentation][docs-link]
+
+## ⚠️ Security Warning: [Hazmat!][hazmat-link]
+
+This crate does not ensure ciphertexts are authentic (i.e. by using a MAC to
+verify ciphertext integrity), which can lead to serious vulnerabilities
+if used incorrectly!
+
+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!
+
+## Minimum Supported Rust Version
+
+Rust **1.65** or higher.
+
+Minimum supported Rust version can be changed in the future, but it will be
+done with a minor version bump.
+
+## SemVer Policy
+
+- All on-by-default features of this library are covered by SemVer
+- MSRV is considered exempt from SemVer as noted above
+
+## License
+
+Licensed under either of:
+
+ * [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0)
+ * [MIT license](http://opensource.org/licenses/MIT)
+
+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.
+
+[//]: # (badges)
+
+[crate-image]: https://img.shields.io/crates/v/xtea.svg
+[crate-link]: https://crates.io/crates/xtea
+[docs-image]: https://docs.rs/xtea/badge.svg
+[docs-link]: https://docs.rs/xtea/
+[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
+[rustc-image]: https://img.shields.io/badge/rustc-1.65+-blue.svg
+[hazmat-image]: https://img.shields.io/badge/crypto-hazmat%E2%9A%A0-red.svg
+[hazmat-link]: https://github.com/RustCrypto/meta/blob/master/HAZMAT.md
+[chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
+[chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260039-block-ciphers
+[build-image]: https://github.com/RustCrypto/block-ciphers/workflows/xtea/badge.svg?branch=master&event=push
+[build-link]: https://github.com/RustCrypto/block-ciphers/actions?query=workflow%3Axtea
+
+[//]: # (general links)
+
+[1]: https://en.wikipedia.org/wiki/XTEA

xtea/benches/mod.rs

@@ -0,0 +1,8 @@
+#![feature(test)]
+extern crate test;
+
+use cipher::{block_decryptor_bench, block_encryptor_bench};
+use xtea::Xtea;
+
+block_encryptor_bench!(Key: Xtea, xtea_encrypt_block, xtea_encrypt_blocks);
+block_decryptor_bench!(Key: Xtea, xtea_decrypt_block, xtea_decrypt_blocks);

xtea/src/consts.rs

@@ -0,0 +1,2 @@
+pub const DELTA: u32 = 0x9e3779b9;
+pub const ROUNDS: usize = 32;