saymrwulf/risc0-curve25519-dalek-source
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remove mul; remove derive default on SharedSecret; rename decode to clamp

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This commit is contained in:
DebugSteven 2018-12-03 13:27:35 -05:00
parent 7f822ff3dd
commit ccf7e5bb57
1 changed files with 4 additions and 16 deletions
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20
src/x25519.rs
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@ -12,8 +12,6 @@
//! This implements x25519 key exchange as specified by Mike Hamburg
//! and Adam Langley in [RFC7748](https://tools.ietf.org/html/rfc7748).
use core::ops::Mul;
use clear_on_drop::clear::Clear;
use curve25519_dalek::constants::ED25519_BASEPOINT_TABLE;
@ -39,15 +37,6 @@ impl Drop for EphemeralSecret {
}
}
/// Multiply this `EphemeralPublic` key by a `EphemeralSecret` key.
impl<'a, 'b> Mul<&'b EphemeralSecret> for &'a EphemeralPublic {
type Output = EphemeralPublic;
fn mul(self, secret: &'b EphemeralSecret) -> EphemeralPublic {
EphemeralPublic(self.0 * secret.0)
}
}
impl EphemeralSecret {
/// Utility function to make it easier to call `x25519()` with
/// an ephemeral secret key and montegomery point as input and
@ -64,7 +53,7 @@ impl EphemeralSecret {
csprng.fill_bytes(&mut bytes);
EphemeralSecret(decode_scalar(&bytes))
EphemeralSecret(clamp_scalar(&bytes))
}
}
@ -80,7 +69,6 @@ impl<'a> From<&'a EphemeralSecret> for EphemeralPublic {
/// A DH SharedSecret
#[repr(C)]
#[derive(Default)] // we derive Default in order to use the clear() method in Drop
pub struct SharedSecret(pub (crate) MontgomeryPoint);
/// Overwrite shared secret material with null bytes when it goes out of scope.
@ -94,7 +82,7 @@ impl SharedSecret {
/// View this shared secret key as a byte array.
#[inline]
pub fn as_bytes<'a>(&'a self) -> &'a [u8; 32] {
pub fn as_bytes(&self) -> &[u8; 32] {
&self.0.as_bytes()
}
}
@ -107,7 +95,7 @@ impl SharedSecret {
/// # Returns
///
/// A `Scalar`.
fn decode_scalar(scalar: &[u8; 32]) -> Scalar {
fn clamp_scalar(scalar: &[u8; 32]) -> Scalar {
let mut s: [u8; 32] = scalar.clone();
s[0] &= 248;
@ -119,7 +107,7 @@ fn decode_scalar(scalar: &[u8; 32]) -> Scalar {
/// The x25519 function, as specified in RFC7748.
fn x25519(scalar: &Scalar, point: &MontgomeryPoint) -> MontgomeryPoint {
let k: Scalar = decode_scalar(scalar.as_bytes());
let k: Scalar = clamp_scalar(scalar.as_bytes());
(k * point)
}