saymrwulf/risc0-curve25519-dalek-source
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Merge branch 'release/1.0.0'

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Henry de Valence 2020-08-17 19:45:17 -07:00
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9
CHANGELOG.md
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@ -2,6 +2,15 @@
Entries are listed in reverse chronological order.
## 1.0.0
* Widen generic bound on `EphemeralSecret::new` and `StaticSecret::new` to
allow owned as well as borrowed RNGs.
* Add `PublicKey::to_bytes` and `SharedSecret::to_bytes`, returning owned byte
arrays, complementing the existing `as_bytes` methods returning references.
* Remove mention of deprecated `rand_os` crate from examples.
* Clarify `EphemeralSecret`/`StaticSecret` distinction in documentation.
## 0.6.0
* Updates `rand_core` version to `0.5`.

9
Cargo.toml
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@ -1,8 +1,11 @@
[package]
name = "x25519-dalek"
edition = "2018"
# Be sure to update the version in README.md
version = "0.6.0"
# Before changing this:
# - update version in README.md
# - update html_root_url
# - update CHANGELOG
version = "1.0.0"
authors = [
"Isis Lovecruft <isis@patternsinthevoid.net>",
"DebugSteven <debugsteven@gmail.com>",
@ -39,7 +42,7 @@ zeroize = { version = "1", default-features = false, features = ["zeroize_derive
[dev-dependencies]
bincode = "1"
criterion = "0.2"
criterion = "0.3.0"
[[bench]]
name = "x25519"

63
README.md
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@ -31,45 +31,60 @@ the rest of the afternoon nomming some yummy pie!
First, Alice uses `EphemeralSecret::new()` and then
`PublicKey::from()` to produce her secret and public keys:
```rust,ignore
extern crate rand_os;
extern crate x25519_dalek;
```rust
use rand_core::OsRng;
use x25519_dalek::{EphemeralSecret, PublicKey};
use rand_os::OsRng;
use x25519_dalek::EphemeralSecret;
use x25519_dalek::PublicKey;
let mut alice_csprng = OsRng::new().unwrap();
let alice_secret = EphemeralSecret::new(&mut alice_csprng);
let alice_public = PublicKey::from(&alice_secret);
let alice_secret = EphemeralSecret::new(OsRng);
let alice_public = PublicKey::from(&alice_secret);
```
Bob does the same:
```rust,ignore
let mut bob_csprng = OsRng::new().unwrap();
let bob_secret = EphemeralSecret::new(&mut bob_csprng);
let bob_public = PublicKey::from(&bob_secret);
```rust
# use rand_core::OsRng;
# use x25519_dalek::{EphemeralSecret, PublicKey};
let bob_secret = EphemeralSecret::new(OsRng);
let bob_public = PublicKey::from(&bob_secret);
```
Alice meows across the room, telling `alice_public` to Bob, and Bob
loudly meows `bob_public` back to Alice. Alice now computes her
shared secret with Bob by doing:
```rust,ignore
```rust
# use rand_core::OsRng;
# use x25519_dalek::{EphemeralSecret, PublicKey};
# let alice_secret = EphemeralSecret::new(OsRng);
# let alice_public = PublicKey::from(&alice_secret);
# let bob_secret = EphemeralSecret::new(OsRng);
# let bob_public = PublicKey::from(&bob_secret);
let alice_shared_secret = alice_secret.diffie_hellman(&bob_public);
```
Similarly, Bob computes a shared secret by doing:
```rust,ignore
```rust
# use rand_core::OsRng;
# use x25519_dalek::{EphemeralSecret, PublicKey};
# let alice_secret = EphemeralSecret::new(OsRng);
# let alice_public = PublicKey::from(&alice_secret);
# let bob_secret = EphemeralSecret::new(OsRng);
# let bob_public = PublicKey::from(&bob_secret);
let bob_shared_secret = bob_secret.diffie_hellman(&alice_public);
```
These secrets are the same:
```rust,ignore
```rust
# use rand_core::OsRng;
# use x25519_dalek::{EphemeralSecret, PublicKey};
# let alice_secret = EphemeralSecret::new(OsRng);
# let alice_public = PublicKey::from(&alice_secret);
# let bob_secret = EphemeralSecret::new(OsRng);
# let bob_public = PublicKey::from(&bob_secret);
# let alice_shared_secret = alice_secret.diffie_hellman(&bob_public);
# let bob_shared_secret = bob_secret.diffie_hellman(&alice_public);
assert_eq!(alice_shared_secret.as_bytes(), bob_shared_secret.as_bytes());
```
@ -86,8 +101,8 @@ and load a long-term secret key.
To install, add the following to your project's `Cargo.toml`:
```toml
[dependencies.x25519-dalek]
version = "0.6"
[dependencies]
x25519-dalek = "1"
```
# Documentation
@ -105,3 +120,11 @@ attempt to prevent software side-channels.
copyright © Amy Wibowo ([@sailorhg](https://twitter.com/sailorhg))
[rfc7748]: https://tools.ietf.org/html/rfc7748
# See also
- [crypto_box]: pure Rust public-key authenticated encryption compatible with
the NaCl family of encryption libraries (libsodium, TweetNaCl) which uses
`x25519-dalek` for key agreement
[crypto_box]: https://github.com/RustCrypto/AEADs/tree/master/crypto_box

1
src/lib.rs
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@ -20,6 +20,7 @@
#![cfg_attr(feature = "nightly", deny(missing_docs))]
#![cfg_attr(feature = "nightly", doc(include = "../README.md"))]
#![doc(html_logo_url = "https://doc.dalek.rs/assets/dalek-logo-clear.png")]
#![doc(html_root_url = "https://docs.rs/x25519-dalek/1.0.0")]
//! Note that docs will only build on nightly Rust until
//! `feature(external_doc)` is stabilized.

90
src/x25519.rs
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@ -23,8 +23,7 @@ use rand_core::RngCore;
use zeroize::Zeroize;
/// A `PublicKey` is the corresponding public key converted from
/// an `EphemeralSecret` or a `StaticSecret` key.
/// A Diffie-Hellman public key, corresponding to an [`EphemeralSecret`] or [`StaticSecret`] key.
#[cfg_attr(feature = "serde", serde(crate = "our_serde"))]
#[cfg_attr(
feature = "serde",
@ -41,6 +40,12 @@ impl From<[u8; 32]> for PublicKey {
}
impl PublicKey {
/// Convert this public key to a byte array.
#[inline]
pub fn to_bytes(&self) -> [u8; 32] {
self.0.to_bytes()
}
/// View this public key as a byte array.
#[inline]
pub fn as_bytes(&self) -> &[u8; 32] {
@ -48,24 +53,27 @@ impl PublicKey {
}
}
/// A `EphemeralSecret` is a short lived Diffie-Hellman secret key
/// used to create a `SharedSecret` when given their `PublicKey`.
/// A short-lived Diffie-Hellman secret key that can only be used to compute a single
/// [`SharedSecret`].
///
/// This type is identical to the [`StaticSecret`] type, except that the
/// [`EphemeralSecret::diffie_hellman`] method consumes and then wipes the secret key, and there
/// are no serialization methods defined. This means that [`EphemeralSecret`]s can only be
/// generated from fresh randomness by [`EphemeralSecret::new`] and the compiler statically checks
/// that the resulting secret is used at most once.
#[derive(Zeroize)]
#[zeroize(drop)]
pub struct EphemeralSecret(pub(crate) Scalar);
impl EphemeralSecret {
/// Perform a Diffie-Hellman key agreement between `self` and
/// `their_public` key to produce a `SharedSecret`.
/// `their_public` key to produce a [`SharedSecret`].
pub fn diffie_hellman(self, their_public: &PublicKey) -> SharedSecret {
SharedSecret(self.0 * their_public.0)
}
/// Generate an x25519 `EphemeralSecret` key.
pub fn new<T>(csprng: &mut T) -> Self
where
T: RngCore + CryptoRng,
{
/// Generate an x25519 [`EphemeralSecret`] key.
pub fn new<T: RngCore + CryptoRng>(mut csprng: T) -> Self {
let mut bytes = [0u8; 32];
csprng.fill_bytes(&mut bytes);
@ -75,16 +83,27 @@ impl EphemeralSecret {
}
impl<'a> From<&'a EphemeralSecret> for PublicKey {
/// Given an x25519 `EphemeralSecret` key, compute its corresponding
/// `PublicKey` key.
/// Given an x25519 [`EphemeralSecret`] key, compute its corresponding [`PublicKey`].
fn from(secret: &'a EphemeralSecret) -> PublicKey {
PublicKey((&ED25519_BASEPOINT_TABLE * &secret.0).to_montgomery())
}
}
/// A `StaticSecret` is a static Diffie-Hellman secret key that
/// can be saved and loaded to create a `SharedSecret` when given
/// their `PublicKey`.
/// A Diffie-Hellman secret key that can be used to compute multiple [`SharedSecret`]s.
///
/// This type is identical to the [`EphemeralSecret`] type, except that the
/// [`StaticSecret::diffie_hellman`] method does not consume the secret key, and the type provides
/// serialization methods to save and load key material. This means that the secret may be used
/// multiple times (but does not *have to be*).
///
/// Some protocols, such as Noise, already handle the static/ephemeral distinction, so the
/// additional guarantees provided by [`EphemeralSecret`] are not helpful or would cause duplicate
/// code paths. In this case, it may be useful to
/// ```rust,ignore
/// use x25519_dalek::StaticSecret as SecretKey;
/// ```
/// since the only difference between the two is that [`StaticSecret`] does not enforce at
/// compile-time that the key is only used once.
#[cfg_attr(feature = "serde", serde(crate = "our_serde"))]
#[cfg_attr(
feature = "serde",
@ -103,11 +122,8 @@ impl StaticSecret {
SharedSecret(&self.0 * their_public.0)
}
/// Generate a x25519 `StaticSecret` key.
pub fn new<T>(csprng: &mut T) -> Self
where
T: RngCore + CryptoRng,
{
/// Generate an x25519 key.
pub fn new<T: RngCore + CryptoRng>(mut csprng: T) -> Self {
let mut bytes = [0u8; 32];
csprng.fill_bytes(&mut bytes);
@ -115,34 +131,41 @@ impl StaticSecret {
StaticSecret(clamp_scalar(bytes))
}
/// Save a x25519 `StaticSecret` key's bytes.
/// Extract this key's bytes for serialization.
pub fn to_bytes(&self) -> [u8; 32] {
self.0.to_bytes()
}
}
impl From<[u8; 32]> for StaticSecret {
/// Load a `StaticSecret` from a byte array.
/// Load a secret key from a byte array.
fn from(bytes: [u8; 32]) -> StaticSecret {
StaticSecret(clamp_scalar(bytes))
}
}
impl<'a> From<&'a StaticSecret> for PublicKey {
/// Given an x25519 `StaticSecret` key, compute its corresponding
/// `PublicKey` key.
/// Given an x25519 [`StaticSecret`] key, compute its corresponding [`PublicKey`].
fn from(secret: &'a StaticSecret) -> PublicKey {
PublicKey((&ED25519_BASEPOINT_TABLE * &secret.0).to_montgomery())
}
}
/// A `SharedSecret` is a Diffie-Hellman shared secret that’s generated
/// from your `EphemeralSecret` or `StaticSecret` and their `PublicKey`.
/// The result of a Diffie-Hellman key exchange.
///
/// Each party computes this using their [`EphemeralSecret`] or [`StaticSecret`] and their
/// counterparty's [`PublicKey`].
#[derive(Zeroize)]
#[zeroize(drop)]
pub struct SharedSecret(pub(crate) MontgomeryPoint);
impl SharedSecret {
/// Convert this shared secret to a byte array.
#[inline]
pub fn to_bytes(&self) -> [u8; 32] {
self.0.to_bytes()
}
/// View this shared secret key as a byte array.
#[inline]
pub fn as_bytes(&self) -> &[u8; 32] {
@ -205,21 +228,6 @@ mod test {
use rand_core::OsRng;
// This was previously a doctest but it got moved to the README to
// avoid duplication where it then wasn't being run, so now it
// lives here.
#[test]
fn alice_and_bob() {
let alice_secret = EphemeralSecret::new(&mut OsRng);
let alice_public = PublicKey::from(&alice_secret);
let bob_secret = EphemeralSecret::new(&mut OsRng);
let bob_public = PublicKey::from(&bob_secret);
let alice_shared_secret = alice_secret.diffie_hellman(&bob_public);
let bob_shared_secret = bob_secret.diffie_hellman(&alice_public);
assert_eq!(alice_shared_secret.as_bytes(), bob_shared_secret.as_bytes());
}
#[test]
fn byte_basepoint_matches_edwards_scalar_mul() {
let mut scalar_bytes = [0x37; 32];