Introduce PrivateKey associated type to CipherSuite

examples/digital_locker.rs

@@ -32,6 +32,7 @@ use std::process::exit;
 
 use opaque_ke::{
     ciphersuite::CipherSuite,
+    keypair::PrivateKey,
     rand::{rngs::OsRng, RngCore},
     ClientLogin, ClientLoginFinishParameters, ClientRegistration,
     ClientRegistrationFinishParameters, CredentialFinalization, CredentialRequest,
@@ -48,6 +49,7 @@ impl CipherSuite for Default {
     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
     type Hash = sha2::Sha512;
     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+    type PrivateKey = PrivateKey<Self::Group>;
 }
 
 struct Locker {

examples/simple_login.rs

@@ -26,10 +26,11 @@ use std::collections::HashMap;
 use std::process::exit;
 
 use opaque_ke::{
-    ciphersuite::CipherSuite, rand::rngs::OsRng, ClientLogin, ClientLoginFinishParameters,
-    ClientRegistration, ClientRegistrationFinishParameters, CredentialFinalization,
-    CredentialRequest, CredentialResponse, RegistrationRequest, RegistrationResponse,
-    RegistrationUpload, ServerLogin, ServerLoginStartParameters, ServerRegistration, ServerSetup,
+    ciphersuite::CipherSuite, keypair::PrivateKey, rand::rngs::OsRng, ClientLogin,
+    ClientLoginFinishParameters, ClientRegistration, ClientRegistrationFinishParameters,
+    CredentialFinalization, CredentialRequest, CredentialResponse, RegistrationRequest,
+    RegistrationResponse, RegistrationUpload, ServerLogin, ServerLoginStartParameters,
+    ServerRegistration, ServerSetup,
 };
 
 // The ciphersuite trait allows to specify the underlying primitives
@@ -41,6 +42,7 @@ impl CipherSuite for Default {
     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
     type Hash = sha2::Sha512;
     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+    type PrivateKey = PrivateKey<Self::Group>;
 }
 
 // Password-based registration between a client and server

src/ciphersuite.rs

@@ -6,8 +6,8 @@
 //! Defines the CipherSuite trait to specify the underlying primitives for OPAQUE
 
 use crate::{
-    hash::Hash, key_exchange::traits::KeyExchange, map_to_curve::GroupWithMapToCurve,
-    slow_hash::SlowHash,
+    hash::Hash, key_exchange::traits::KeyExchange, keypair::SecretKey,
+    map_to_curve::GroupWithMapToCurve, slow_hash::SlowHash,
 };
 use digest::Digest;
 
@@ -31,4 +31,6 @@ pub trait CipherSuite {
     type Hash: Hash;
     /// A slow hashing function, typically used for password hashing
     type SlowHash: SlowHash<Self::Hash>;
+    /// A private key container, allows remote key implementations
+    type PrivateKey: SecretKey<Self::Group>;
 }

src/key_exchange/traits.rs

@@ -8,7 +8,7 @@ use crate::{
     errors::{PakeError, ProtocolError},
     group::Group,
     hash::Hash,
-    keypair::{PrivateKey, PublicKey},
+    keypair::{PrivateKey, PublicKey, SecretKey},
 };
 use rand::{CryptoRng, RngCore};
 use zeroize::Zeroize;
@@ -25,13 +25,13 @@ pub trait KeyExchange<D: Hash, G: Group> {
     ) -> Result<(Self::KE1State, Self::KE1Message), ProtocolError>;
 
     #[allow(clippy::too_many_arguments, clippy::type_complexity)]
-    fn generate_ke2<R: RngCore + CryptoRng>(
+    fn generate_ke2<R: RngCore + CryptoRng, S: SecretKey<G>>(
         rng: &mut R,
         l1_bytes: Vec<u8>,
         l2_bytes: Vec<u8>,
         ke1_message: Self::KE1Message,
         client_s_pk: PublicKey<G>,
-        server_s_sk: PrivateKey<G>,
+        server_s_sk: S,
         id_u: Vec<u8>,
         id_s: Vec<u8>,
         context: Vec<u8>,

src/key_exchange/tripledh.rs

@@ -13,7 +13,7 @@ use crate::{
     group::Group,
     hash::Hash,
     key_exchange::traits::{FromBytes, KeyExchange, ToBytes, ToBytesWithPointers},
-    keypair::{KeyPair, PrivateKey, PublicKey, SizedBytesExt},
+    keypair::{KeyPair, PrivateKey, PublicKey, SecretKey, SizedBytesExt},
     serialization::serialize,
 };
 use digest::{Digest, FixedOutput};
@@ -70,13 +70,13 @@ impl<D: Hash, G: Group> KeyExchange<D, G> for TripleDH {
     }
 
     #[allow(clippy::type_complexity)]
-    fn generate_ke2<R: RngCore + CryptoRng>(
+    fn generate_ke2<R: RngCore + CryptoRng, S: SecretKey<G>>(
         rng: &mut R,
         serialized_credential_request: Vec<u8>,
         l2_bytes: Vec<u8>,
         ke1_message: Self::KE1Message,
         client_s_pk: PublicKey<G>,
-        server_s_sk: PrivateKey<G>,
+        server_s_sk: S,
         id_u: Vec<u8>,
         id_s: Vec<u8>,
         context: Vec<u8>,
@@ -94,7 +94,7 @@ impl<D: Hash, G: Group> KeyExchange<D, G> for TripleDH {
             .chain(&server_nonce[..])
             .chain(&server_e_kp.public().to_arr());
 
-        let (session_key, km2, km3) = derive_3dh_keys::<D, G>(
+        let (session_key, km2, km3) = derive_3dh_keys::<D, G, S>(
             TripleDHComponents {
                 pk1: ke1_message.client_e_pk.clone(),
                 sk1: server_e_kp.private().clone(),
@@ -148,7 +148,7 @@ impl<D: Hash, G: Group> KeyExchange<D, G> for TripleDH {
             .chain(&l2_component[..])
             .chain(&ke2_message.to_bytes_without_info_or_mac());
 
-        let (session_key, km2, km3) = derive_3dh_keys::<D, G>(
+        let (session_key, km2, km3) = derive_3dh_keys::<D, G, PrivateKey<G>>(
             TripleDHComponents {
                 pk1: ke2_message.server_e_pk.clone(),
                 sk1: ke1_state.client_e_sk.clone(),
@@ -408,11 +408,11 @@ impl<G: Group, HashLen: ArrayLength<u8>> FromBytes for Ke2Message<G, HashLen> {
 
 #[allow(clippy::upper_case_acronyms)]
 // The triple of public and private components used in the 3DH computation
-struct TripleDHComponents<G: Group> {
+struct TripleDHComponents<G: Group, S: SecretKey<G>> {
     pk1: PublicKey<G>,
     sk1: PrivateKey<G>,
     pk2: PublicKey<G>,
-    sk2: PrivateKey<G>,
+    sk2: S,
     pk3: PublicKey<G>,
     sk3: PrivateKey<G>,
 }
@@ -453,14 +453,14 @@ impl<HashLen: ArrayLength<u8>> FromBytes for Ke3Message<HashLen> {
 
 // Internal function which takes the public and private components of the client and server keypairs, along
 // with some auxiliary metadata, to produce the session key and two MAC keys
-fn derive_3dh_keys<D: Hash, G: Group>(
-    dh: TripleDHComponents<G>,
+fn derive_3dh_keys<D: Hash, G: Group, S: SecretKey<G>>(
+    dh: TripleDHComponents<G, S>,
     hashed_derivation_transcript: &[u8],
 ) -> Result<TripleDHDerivationResult<D>, ProtocolError> {
     let ikm: Vec<u8> = [
-        &KeyPair::<G>::diffie_hellman(dh.pk1, dh.sk1)?[..],
-        &KeyPair::<G>::diffie_hellman(dh.pk2, dh.sk2)?[..],
-        &KeyPair::<G>::diffie_hellman(dh.pk3, dh.sk3)?[..],
+        &dh.sk1.diffie_hellman(dh.pk1)?[..],
+        &dh.sk2.diffie_hellman(dh.pk2)?[..],
+        &dh.sk3.diffie_hellman(dh.pk3)?[..],
     ]
     .concat();
 

src/keypair.rs

@@ -7,7 +7,7 @@
 
 #![allow(unsafe_code)]
 
-use crate::errors::InternalPakeError;
+use crate::errors::{InternalPakeError, PakeError, ProtocolError};
 use crate::group::Group;
 #[cfg(test)]
 use generic_array::typenum::Unsigned;
@@ -37,65 +37,74 @@ impl<T> SizedBytesExt for T where T: SizedBytes {}
 #[cfg_attr(
     feature = "serialize",
     derive(serde::Deserialize, serde::Serialize),
-    serde(bound = "")
+    serde(bound(
+        deserialize = "S: serde::Deserialize<'de>",
+        serialize = "S: serde::Serialize"
+    ))
 )]
-pub struct KeyPair<G: Group> {
+pub struct KeyPair<G: Group, S: SecretKey<G> = PrivateKey<G>> {
     pk: PublicKey<G>,
-    sk: PrivateKey<G>,
+    sk: S,
 }
 
-impl_clone_for!(
-    struct KeyPair<G: Group>,
-    [pk, sk],
-);
-impl_debug_eq_hash_for!(
-    struct KeyPair<G: Group>,
-    [pk, sk],
-);
+impl<G: Group, S: SecretKey<G>> Clone for KeyPair<G, S> {
+    fn clone(&self) -> Self {
+        Self {
+            pk: self.pk.clone(),
+            sk: self.sk.clone(),
+        }
+    }
+}
+
+impl<G: Group, S: SecretKey<G> + Debug> Debug for KeyPair<G, S> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("KeyPair")
+            .field("pk", &self.pk)
+            .field("sk", &self.sk)
+            .finish()
+    }
+}
+
+impl<G: Group, S: SecretKey<G> + PartialEq> PartialEq for KeyPair<G, S> {
+    fn eq(&self, other: &Self) -> bool {
+        self.pk.eq(&other.pk) && self.sk.eq(&other.sk)
+    }
+}
+
+impl<G: Group, S: SecretKey<G> + Eq> Eq for KeyPair<G, S> {}
+
+impl<G: Group, S: SecretKey<G> + std::hash::Hash> std::hash::Hash for KeyPair<G, S> {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.pk.hash(state);
+        self.sk.hash(state);
+    }
+}
 
 // This can't be derived because of the use of a generic parameter
-impl<G: Group> Zeroize for KeyPair<G> {
+impl<G: Group, S: SecretKey<G>> Zeroize for KeyPair<G, S> {
     fn zeroize(&mut self) {
         self.pk.zeroize();
         self.sk.zeroize();
     }
 }
 
-impl<G: Group> Drop for KeyPair<G> {
+impl<G: Group, S: SecretKey<G>> Drop for KeyPair<G, S> {
     fn drop(&mut self) {
         self.zeroize();
     }
 }
 
-impl<G: Group> KeyPair<G> {
+impl<G: Group, S: SecretKey<G>> KeyPair<G, S> {
     /// The public key component
     pub fn public(&self) -> &PublicKey<G> {
         &self.pk
     }
 
     /// The private key component
-    pub fn private(&self) -> &PrivateKey<G> {
+    pub fn private(&self) -> &S {
         &self.sk
     }
 
-    /// Generating a random key pair given a cryptographic rng
-    pub(crate) fn generate_random<R: RngCore + CryptoRng>(rng: &mut R) -> Self {
-        let sk = G::random_nonzero_scalar(rng);
-        let sk_bytes = G::scalar_as_bytes(sk);
-        let pk = G::base_point().mult_by_slice(&sk_bytes);
-        Self {
-            pk: PublicKey(Key(pk.to_arr())),
-            sk: PrivateKey(Key(sk_bytes)),
-        }
-    }
-
-    /// Obtaining a public key from secret bytes. At all times, we should have
-    /// &public_from_private(self.private()) == self.public()
-    pub(crate) fn public_from_private(bytes: &PrivateKey<G>) -> PublicKey<G> {
-        let bytes_data = GenericArray::<u8, G::ScalarLen>::from_slice(&bytes.0[..]);
-        PublicKey(Key(G::base_point().mult_by_slice(bytes_data).to_arr()))
-    }
-
     /// Check whether a public key is valid. This is meant to be applied on
     /// material provided through the network which fits the key
     /// representation (i.e. can be mapped to a curve point), but presents
@@ -104,23 +113,25 @@ impl<G: Group> KeyPair<G> {
         G::from_element_slice(GenericArray::from_slice(&key.0)).map(|_| key)
     }
 
-    /// Computes the diffie hellman function on a public key and private key
-    pub(crate) fn diffie_hellman(
-        pk: PublicKey<G>,
-        sk: PrivateKey<G>,
-    ) -> Result<Vec<u8>, InternalPakeError> {
-        let pk_data = GenericArray::<u8, G::ElemLen>::from_slice(&pk.0[..]);
-        let point = G::from_element_slice(pk_data)?;
-        let secret_data = GenericArray::<u8, G::ScalarLen>::from_slice(&sk.0[..]);
-        Ok(G::mult_by_slice(&point, secret_data).to_arr().to_vec())
-    }
-
     /// Obtains a KeyPair from a slice representing the private key
-    pub fn from_private_key_slice(input: &[u8]) -> Result<Self, InternalPakeError> {
-        let sk = PrivateKey(Key(GenericArray::clone_from_slice(input)));
-        let pk = Self::public_from_private(&sk);
+    pub fn from_private_key_slice(input: &[u8]) -> Result<Self, ProtocolError> {
+        let sk = S::deserialize(input)?;
+        let pk = sk.public_key()?;
         Ok(Self { pk, sk })
     }
+}
+
+impl<G: Group> KeyPair<G> {
+    /// Generating a random key pair given a cryptographic rng
+    pub(crate) fn generate_random<R: RngCore + CryptoRng>(rng: &mut R) -> Self {
+        let sk = G::random_nonzero_scalar(rng);
+        let sk_bytes = G::scalar_as_bytes(sk);
+        let pk = G::base_point().mult_by_slice(&sk_bytes);
+        Self {
+            pk: PublicKey(Key(pk.to_arr())),
+            sk: PrivateKey(Key(sk_bytes)),
+        }
+    }
 
     #[cfg(test)]
     pub fn as_byte_ptrs(&self) -> Vec<(*const u8, usize)> {
@@ -263,6 +274,45 @@ impl<G: Group> SizedBytes for PrivateKey<G> {
     }
 }
 
+/// A trait specifying the requirements for a private key container
+pub trait SecretKey<G: Group>: Clone + Sized + Zeroize {
+    /// Diffie-Hellman key exchange implementation
+    fn diffie_hellman(&self, pk: PublicKey<G>) -> Result<Vec<u8>, InternalPakeError>;
+
+    /// Returns public key from private key
+    fn public_key(&self) -> Result<PublicKey<G>, InternalPakeError>;
+
+    /// Serialization into bytes
+    fn serialize(&self) -> Vec<u8>;
+
+    /// Deserialization from bytes
+    fn deserialize(input: &[u8]) -> Result<Self, ProtocolError>;
+}
+
+impl<G: Group> SecretKey<G> for PrivateKey<G> {
+    fn diffie_hellman(&self, pk: PublicKey<G>) -> Result<Vec<u8>, InternalPakeError> {
+        let pk_data = GenericArray::<u8, G::ElemLen>::from_slice(&pk.0[..]);
+        let point = G::from_element_slice(pk_data)?;
+        let secret_data = GenericArray::<u8, G::ScalarLen>::from_slice(&self.0[..]);
+        Ok(G::mult_by_slice(&point, secret_data).to_arr().to_vec())
+    }
+
+    fn public_key(&self) -> Result<PublicKey<G>, InternalPakeError> {
+        let bytes_data = GenericArray::<u8, G::ScalarLen>::from_slice(&self.0[..]);
+        Ok(PublicKey(Key(G::base_point()
+            .mult_by_slice(bytes_data)
+            .to_arr())))
+    }
+
+    fn serialize(&self) -> Vec<u8> {
+        self.to_vec()
+    }
+
+    fn deserialize(input: &[u8]) -> Result<Self, ProtocolError> {
+        PrivateKey::from_bytes(input).map_err(|_| PakeError::SerializationError.into())
+    }
+}
+
 /// Wrapper around a Key to enforce that it's a public one.
 #[cfg_attr(feature = "serialize", derive(serde::Deserialize, serde::Serialize))]
 #[repr(transparent)]
@@ -364,15 +414,15 @@ mod tests {
         fn test_ristretto_pub_from_priv(kp in KeyPair::<RistrettoPoint>::uniform_keypair_strategy()) {
             let pk = kp.public();
             let sk = kp.private();
-            prop_assert_eq!(&KeyPair::<RistrettoPoint>::public_from_private(sk), pk);
+            prop_assert_eq!(&sk.public_key()?, pk);
         }
 
         #[test]
         fn test_ristretto_dh(kp1 in KeyPair::<RistrettoPoint>::uniform_keypair_strategy(),
                           kp2 in KeyPair::<RistrettoPoint>::uniform_keypair_strategy()) {
 
-            let dh1 = KeyPair::<RistrettoPoint>::diffie_hellman(kp1.public().clone(), kp2.private().clone())?;
-            let dh2 = KeyPair::<RistrettoPoint>::diffie_hellman(kp2.public().clone(), kp1.private().clone())?;
+            let dh1 = kp2.private().diffie_hellman(kp1.public().clone())?;
+            let dh2 = kp1.private().diffie_hellman(kp2.public().clone())?;
 
             prop_assert_eq!(dh1, dh2);
         }

src/lib.rs

@@ -26,6 +26,7 @@
 //!     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //!     type Hash = sha2::Sha512;
 //!     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//!     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! }
 //! ```
 //! See [examples/simple_login.rs](https://github.com/novifinancial/opaque-ke/blob/master/examples/simple_login.rs)
@@ -47,6 +48,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! use rand::{rngs::OsRng, RngCore};
 //! let mut rng = OsRng;
@@ -79,6 +81,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! use opaque_ke::ClientRegistration;
 //! use rand::{rngs::OsRng, RngCore};
@@ -109,6 +112,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -146,6 +150,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -184,6 +189,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -226,6 +232,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! use opaque_ke::ClientLogin;
@@ -259,6 +266,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -312,6 +320,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -357,6 +366,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -432,6 +442,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -509,6 +520,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -574,6 +586,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -611,6 +624,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;
@@ -660,6 +674,7 @@
 //! #     type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDH;
 //! #     type Hash = sha2::Sha512;
 //! #     type SlowHash = opaque_ke::slow_hash::NoOpHash;
+//! #     type PrivateKey = opaque_ke::keypair::PrivateKey<Self::Group>;
 //! # }
 //! # use rand::{rngs::OsRng, RngCore};
 //! # let mut client_rng = OsRng;

src/opaque.rs

@@ -12,7 +12,7 @@ use crate::{
     group::Group,
     hash::Hash,
     key_exchange::traits::{FromBytes, KeyExchange, ToBytesWithPointers},
-    keypair::{KeyPair, PrivateKey, PublicKey},
+    keypair::{KeyPair, PrivateKey, PublicKey, SecretKey},
     map_to_curve::GroupWithMapToCurve,
     oprf,
     serialization::{serialize, tokenize},
@@ -37,14 +37,21 @@ const STR_OPAQUE_DERIVE_KEY_PAIR: &[u8] = b"OPAQUE-DeriveKeyPair";
 // ============
 
 /// The state elements the server holds upon setup
-#[cfg_attr(feature = "serialize", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(
+    feature = "serialize",
+    derive(serde::Deserialize, serde::Serialize),
+    serde(bound(
+        deserialize = "KeyPair<CS::Group, CS::PrivateKey>: serde::Deserialize<'de>",
+        serialize = "KeyPair<CS::Group, CS::PrivateKey>: serde::Serialize"
+    ))
+)]
 pub struct ServerSetup<CS: CipherSuite> {
     oprf_seed: GenericArray<u8, <CS::Hash as Digest>::OutputSize>,
-    keypair: KeyPair<CS::Group>,
+    keypair: KeyPair<CS::Group, CS::PrivateKey>,
     pub(crate) fake_keypair: KeyPair<CS::Group>,
 }
 
-impl<CS: CipherSuite> ServerSetup<CS> {
+impl<CS: CipherSuite<Group = G, PrivateKey = PrivateKey<G>>, G: Group> ServerSetup<CS> {
     /// Generate a new instance of server setup
     pub fn new<R: CryptoRng + RngCore>(rng: &mut R) -> Self {
         let mut seed = vec![0u8; <CS::Hash as Digest>::OutputSize::to_usize()];
@@ -56,13 +63,15 @@ impl<CS: CipherSuite> ServerSetup<CS> {
             fake_keypair: KeyPair::<CS::Group>::generate_random(rng),
         }
     }
+}
 
+impl<CS: CipherSuite> ServerSetup<CS> {
     /// Serialization into bytes
     pub fn serialize(&self) -> Vec<u8> {
         [
             self.oprf_seed.to_vec(),
-            self.keypair.private().to_arr().to_vec(),
-            self.fake_keypair.private().to_arr().to_vec(),
+            self.keypair.private().serialize(),
+            self.fake_keypair.private().serialize(),
         ]
         .concat()
     }
@@ -81,7 +90,7 @@ impl<CS: CipherSuite> ServerSetup<CS> {
     }
 
     /// Returns the keypair
-    pub fn keypair(&self) -> &KeyPair<CS::Group> {
+    pub fn keypair(&self) -> &KeyPair<CS::Group, CS::PrivateKey> {
         &self.keypair
     }
 }
@@ -775,7 +784,7 @@ impl<CS: CipherSuite> ServerLogin<CS> {
         };
 
         let server_s_sk = server_setup.keypair.private();
-        let server_s_pk = KeyPair::<CS::Group>::public_from_private(server_s_sk);
+        let server_s_pk = server_s_sk.public_key()?;
 
         let mut masking_nonce = vec![0u8; 32];
         rng.fill_bytes(&mut masking_nonce);

src/serialization/tests.rs

@@ -12,7 +12,7 @@ use crate::{
         traits::{FromBytes, KeyExchange, ToBytes},
         tripledh::{NonceLen, TripleDH},
     },
-    keypair::{KeyPair, PublicKey},
+    keypair::{KeyPair, PrivateKey, PublicKey},
     serialization::{i2osp, os2ip, serialize},
     *,
 };
@@ -31,6 +31,7 @@ impl CipherSuite for Default {
     type KeyExchange = TripleDH;
     type Hash = sha2::Sha512;
     type SlowHash = crate::slow_hash::NoOpHash;
+    type PrivateKey = PrivateKey<RistrettoPoint>;
 }
 
 const HASH_SIZE: usize = 64; // Because of SHA512

src/tests/full_test.rs

@@ -10,7 +10,7 @@ use crate::{
     errors::*,
     group::Group,
     key_exchange::tripledh::{NonceLen, TripleDH},
-    keypair::KeyPair,
+    keypair::{KeyPair, PrivateKey},
     opaque::*,
     slow_hash::NoOpHash,
     tests::mock_rng::CycleRng,
@@ -33,6 +33,7 @@ impl CipherSuite for RistrettoSha5123dhNoSlowHash {
     type KeyExchange = TripleDH;
     type Hash = sha2::Sha512;
     type SlowHash = NoOpHash;
+    type PrivateKey = PrivateKey<RistrettoPoint>;
 }
 
 pub struct TestVectorParameters {

src/tests/opaque_test_vectors.rs

@@ -21,6 +21,7 @@ impl CipherSuite for Ristretto255Sha512NoSlowHash {
     type KeyExchange = TripleDH;
     type Hash = sha2::Sha512;
     type SlowHash = NoOpHash;
+    type PrivateKey = PrivateKey<RistrettoPoint>;
 }
 
 #[derive(PartialEq)]