From 0cc7d0f9b2e0c8eba446063bb6f846bcf816da9e Mon Sep 17 00:00:00 2001
From: Graham Kelly <gkgoat6700@gmail.com>
Date: Tue, 12 Aug 2025 23:39:45 +0000
Subject: [PATCH 1/2] Expose conversions to and from integer representations to
 allow usage in downstream crates and network protocols.

---
 src/private_key.rs   |  7 ++++---
 src/public_key.rs    |  5 +++++
 src/shared_secret.rs | 25 ++++++++++++++++++++++++-
 3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/private_key.rs b/src/private_key.rs
index 32621e1..fe928da 100644
--- a/src/private_key.rs
+++ b/src/private_key.rs
@@ -25,11 +25,12 @@ impl<const LIMBS: usize, const N: usize, MOD: ConstMontyParams<LIMBS>> PrivateKe
         Self { params, key }
     }
 
-    pub(crate) const fn params(&self) -> CsidhParams<LIMBS, N, MOD> {
+    /// Obtains the parameters used by this`PrivateKey`
+    pub const fn params(&self) -> CsidhParams<LIMBS, N, MOD> {
         self.params
     }
-
-    pub(crate) const fn key(&self) -> [u32; N] {
+    ///Obtains the key material in this `PrivateKey`
+    pub const fn key(&self) -> [u32; N] {
         self.key
     }
 }
diff --git a/src/public_key.rs b/src/public_key.rs
index 64d4da9..274bc55 100644
--- a/src/public_key.rs
+++ b/src/public_key.rs
@@ -54,6 +54,11 @@ where
         }
     }
 
+    ///Creates a foeign public key from this `PublicKey`
+    pub fn to_repr(&self) -> Uint<SAT_LIMBS> {
+        return self.key().to_montgomery();
+    }
+
     pub(crate) const fn key(&self) -> ConstMontyForm<MOD, SAT_LIMBS> {
         self.key
     }
diff --git a/src/shared_secret.rs b/src/shared_secret.rs
index 715cb17..0d16fc2 100644
--- a/src/shared_secret.rs
+++ b/src/shared_secret.rs
@@ -4,7 +4,10 @@ use crypto_bigint::{
     rand_core::CryptoRngCore,
 };
 
-use crate::{csidh::csidh, private_key::PrivateKey, public_key::PublicKey};
+use crate::{
+    CsidhParams, csidh::csidh, montgomery_curve::MontgomeryCurve, private_key::PrivateKey,
+    public_key::PublicKey,
+};
 
 /// A shared secret created with the CSIDH key exchange.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -36,4 +39,24 @@ where
             ),
         }
     }
+
+    /// Constructs a `SharedSecret` from the foreign shared secret, if the secret is valid.
+    #[must_use]
+    pub fn new<const N: usize>(
+        params: CsidhParams<SAT_LIMBS, N, MOD>,
+        shared_secret: Uint<SAT_LIMBS>,
+        rng: &mut impl CryptoRngCore,
+    ) -> Option<Self> {
+        let shared_secret = ConstMontyForm::new(&shared_secret);
+        if MontgomeryCurve::new(params, shared_secret).is_supersingular(rng) {
+            Some(Self { shared_secret })
+        } else {
+            None
+        }
+    }
+
+    ///Creates a foreign shared secret from this `SharedSecret`
+    pub fn to_repr(&self) -> Uint<SAT_LIMBS> {
+        return self.shared_secret.to_montgomery();
+    }
 }

From 7b5fc9216fe0a968bfe8e7b97d7a153044c87311 Mon Sep 17 00:00:00 2001
From: Graham Kelly <gkgoat6700@gmail.com>
Date: Tue, 12 Aug 2025 23:41:02 +0000
Subject: [PATCH 2/2] fix typos

---
 src/private_key.rs | 2 +-
 src/public_key.rs  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/private_key.rs b/src/private_key.rs
index fe928da..659187b 100644
--- a/src/private_key.rs
+++ b/src/private_key.rs
@@ -25,7 +25,7 @@ impl<const LIMBS: usize, const N: usize, MOD: ConstMontyParams<LIMBS>> PrivateKe
         Self { params, key }
     }
 
-    /// Obtains the parameters used by this`PrivateKey`
+    /// Obtains the parameters used by this `PrivateKey`
     pub const fn params(&self) -> CsidhParams<LIMBS, N, MOD> {
         self.params
     }
diff --git a/src/public_key.rs b/src/public_key.rs
index 274bc55..b15baf5 100644
--- a/src/public_key.rs
+++ b/src/public_key.rs
@@ -54,7 +54,7 @@ where
         }
     }
 
-    ///Creates a foeign public key from this `PublicKey`
+    ///Creates a foreign public key from this `PublicKey`
     pub fn to_repr(&self) -> Uint<SAT_LIMBS> {
         return self.key().to_montgomery();
     }