diff --git a/willow/src/shell/ahe.rs b/willow/src/shell/ahe.rs
index 0bc212b..d8e3b27 100644
--- a/willow/src/shell/ahe.rs
+++ b/willow/src/shell/ahe.rs
@@ -391,26 +391,24 @@ pub struct PartialDecryptionMetadata {
 
 macro_rules! impl_proto_traits_single_poly {
     ($type:ty, $proto:ty) => {
-        impl ToProto for $type {
+        impl<Context: AsRef<ShellAhe>> ToProto<Context> for $type {
             type Proto = $proto;
-            type Context = ShellAhe;
 
-            fn to_proto(&self, ctx: &Self::Context) -> Result<Self::Proto, status::StatusError> {
-                let moduli = ahe::get_moduli(&ctx.public_ahe_parameters);
+            fn to_proto(&self, ctx: Context) -> Result<Self::Proto, status::StatusError> {
+                let moduli = ahe::get_moduli(&ctx.as_ref().public_ahe_parameters);
                 let poly_proto = rns_polynomial_to_proto(&self.0, &moduli)?;
                 Ok(proto!($proto { poly: poly_proto }))
             }
         }
 
-        impl FromProto for $type {
+        impl<Context: AsRef<ShellAhe>> FromProto<Context> for $type {
             type Proto = $proto;
-            type Context = ShellAhe;
 
             fn from_proto(
                 proto: impl protobuf::AsView<Proxied = Self::Proto>,
-                ctx: &Self::Context,
+                ctx: Context,
             ) -> Result<Self, status::StatusError> {
-                let moduli = ahe::get_moduli(&ctx.public_ahe_parameters);
+                let moduli = ahe::get_moduli(&ctx.as_ref().public_ahe_parameters);
                 let poly = rns_polynomial_from_proto(proto.as_view().poly(), &moduli)?;
                 Ok(Self(poly))
             }
@@ -424,12 +422,11 @@ impl_proto_traits_single_poly!(PublicKey, ShellAhePublicKey);
 
 macro_rules! impl_proto_traits_vec_poly {
     ($type:ty, $proto:ty) => {
-        impl ToProto for $type {
+        impl<Context: AsRef<ShellAhe>> ToProto<Context> for $type {
             type Proto = $proto;
-            type Context = ShellAhe;
 
-            fn to_proto(&self, ctx: &Self::Context) -> Result<Self::Proto, status::StatusError> {
-                let moduli = ahe::get_moduli(&ctx.public_ahe_parameters);
+            fn to_proto(&self, ctx: Context) -> Result<Self::Proto, status::StatusError> {
+                let moduli = ahe::get_moduli(&ctx.as_ref().public_ahe_parameters);
                 let mut result = proto!($proto {});
                 for poly in &self.0 {
                     result.poly_mut().push(rns_polynomial_to_proto(&poly, &moduli)?);
@@ -438,15 +435,14 @@ macro_rules! impl_proto_traits_vec_poly {
             }
         }
 
-        impl FromProto for $type {
+        impl<Context: AsRef<ShellAhe>> FromProto<Context> for $type {
             type Proto = $proto;
-            type Context = ShellAhe;
 
             fn from_proto(
                 proto: impl protobuf::AsView<Proxied = Self::Proto>,
-                ctx: &Self::Context,
+                ctx: Context,
             ) -> Result<Self, status::StatusError> {
-                let moduli = ahe::get_moduli(&ctx.public_ahe_parameters);
+                let moduli = ahe::get_moduli(&ctx.as_ref().public_ahe_parameters);
                 let polys: Result<Vec<_>, _> = proto
                     .as_view()
                     .poly()
@@ -463,34 +459,38 @@ impl_proto_traits_vec_poly!(PartialDecryption, ShellAhePartialDecryption);
 impl_proto_traits_vec_poly!(PartialDecCiphertext, ShellAhePartialDecCiphertext);
 impl_proto_traits_vec_poly!(RecoverCiphertext, ShellAheRecoverCiphertext);
 
-impl ToProto for Ciphertext {
+impl<Context: AsRef<ShellAhe>> ToProto<Context> for Ciphertext {
     type Proto = ShellAheCiphertext;
-    type Context = ShellAhe;
 
-    fn to_proto(&self, ctx: &Self::Context) -> Result<Self::Proto, status::StatusError> {
+    fn to_proto(&self, ctx: Context) -> Result<Self::Proto, status::StatusError> {
         Ok(proto!(ShellAheCiphertext {
-            component_b: self.component_b.to_proto(ctx)?,
-            component_a: self.component_a.to_proto(ctx)?,
+            component_b: self.component_b.to_proto(&ctx)?,
+            component_a: self.component_a.to_proto(&ctx)?,
         }))
     }
 }
 
-impl FromProto for Ciphertext {
+impl<Context: AsRef<ShellAhe>> FromProto<Context> for Ciphertext {
     type Proto = ShellAheCiphertext;
-    type Context = ShellAhe;
 
     fn from_proto(
         proto: impl protobuf::AsView<Proxied = Self::Proto>,
-        ctx: &Self::Context,
+        ctx: Context,
     ) -> Result<Self, status::StatusError> {
         let proto_view = proto.as_view();
         Ok(Ciphertext {
-            component_b: RecoverCiphertext::from_proto(proto_view.component_b(), ctx)?,
-            component_a: PartialDecCiphertext::from_proto(proto_view.component_a(), ctx)?,
+            component_b: RecoverCiphertext::from_proto(proto_view.component_b(), &ctx)?,
+            component_a: PartialDecCiphertext::from_proto(proto_view.component_a(), &ctx)?,
         })
     }
 }
 
+impl AsRef<ShellAhe> for ShellAhe {
+    fn as_ref(&self) -> &ShellAhe {
+        self
+    }
+}
+
 impl AheBase for ShellAhe {
     type SecretKeyShare = SecretKeyShare;
     type PublicKeyShare = PublicKeyShare;
diff --git a/willow/src/shell/kahe.rs b/willow/src/shell/kahe.rs
index ad3022f..8ff84a3 100644
--- a/willow/src/shell/kahe.rs
+++ b/willow/src/shell/kahe.rs
@@ -110,37 +110,34 @@ pub struct SecretKey(pub RnsPolynomial);
 #[derive(Clone)]
 pub struct Ciphertext(pub RnsPolynomialVec);
 
-impl ToProto for SecretKey {
+impl<Context: AsRef<ShellKahe>> ToProto<Context> for SecretKey {
     type Proto = ShellKaheSecretKey;
-    type Context = ShellKahe;
 
-    fn to_proto(&self, ctx: &Self::Context) -> Result<Self::Proto, status::StatusError> {
-        let moduli = kahe::get_moduli(&ctx.public_kahe_parameters);
+    fn to_proto(&self, ctx: Context) -> Result<Self::Proto, status::StatusError> {
+        let moduli = kahe::get_moduli(&ctx.as_ref().public_kahe_parameters);
         let poly_proto = rns_polynomial_to_proto(&self.0, &moduli)?;
         Ok(proto!(ShellKaheSecretKey { poly: poly_proto }))
     }
 }
 
-impl FromProto for SecretKey {
+impl<Context: AsRef<ShellKahe>> FromProto<Context> for SecretKey {
     type Proto = ShellKaheSecretKey;
-    type Context = ShellKahe;
 
     fn from_proto(
         proto: impl protobuf::AsView<Proxied = Self::Proto>,
-        ctx: &Self::Context,
+        ctx: Context,
     ) -> Result<Self, status::StatusError> {
-        let moduli = kahe::get_moduli(&ctx.public_kahe_parameters);
+        let moduli = kahe::get_moduli(&ctx.as_ref().public_kahe_parameters);
         let poly = rns_polynomial_from_proto(proto.as_view().poly(), &moduli)?;
         Ok(Self(poly))
     }
 }
 
-impl ToProto for Ciphertext {
+impl<Context: AsRef<ShellKahe>> ToProto<Context> for Ciphertext {
     type Proto = ShellKaheCiphertext;
-    type Context = ShellKahe;
 
-    fn to_proto(&self, ctx: &Self::Context) -> Result<Self::Proto, status::StatusError> {
-        let moduli = kahe::get_moduli(&ctx.public_kahe_parameters);
+    fn to_proto(&self, ctx: Context) -> Result<Self::Proto, status::StatusError> {
+        let moduli = kahe::get_moduli(&ctx.as_ref().public_kahe_parameters);
         let mut result = proto!(ShellKaheCiphertext {});
         for poly in self.0.iter() {
             result.poly_mut().push(rns_polynomial_to_proto(&poly, &moduli)?);
@@ -149,21 +146,26 @@ impl ToProto for Ciphertext {
     }
 }
 
-impl FromProto for Ciphertext {
+impl<Context: AsRef<ShellKahe>> FromProto<Context> for Ciphertext {
     type Proto = ShellKaheCiphertext;
-    type Context = ShellKahe;
 
     fn from_proto(
         proto: impl protobuf::AsView<Proxied = Self::Proto>,
-        ctx: &Self::Context,
+        ctx: Context,
     ) -> Result<Self, status::StatusError> {
-        let moduli = kahe::get_moduli(&ctx.public_kahe_parameters);
+        let moduli = kahe::get_moduli(&ctx.as_ref().public_kahe_parameters);
         let polys: Result<Vec<_>, _> =
             proto.as_view().poly().iter().map(|p| rns_polynomial_from_proto(p, &moduli)).collect();
         Ok(Ciphertext(rust_vec_to_rns_polynomial_vec(polys?)))
     }
 }
 
+impl AsRef<ShellKahe> for ShellKahe {
+    fn as_ref(&self) -> &ShellKahe {
+        self
+    }
+}
+
 impl KaheBase for ShellKahe {
     type SecretKey = SecretKey;
 
diff --git a/willow/src/traits/proto_serialization.rs b/willow/src/traits/proto_serialization.rs
index a145958..a2bc00f 100644
--- a/willow/src/traits/proto_serialization.rs
+++ b/willow/src/traits/proto_serialization.rs
@@ -15,20 +15,18 @@
 use status::StatusError;
 
 /// Trait for converting a struct to a Protobuf message.
-pub trait ToProto {
+pub trait ToProto<Context = ()> {
     type Proto;
-    type Context;
 
-    fn to_proto(&self, ctx: &Self::Context) -> Result<Self::Proto, StatusError>;
+    fn to_proto(&self, ctx: Context) -> Result<Self::Proto, StatusError>;
 }
 
 /// Trait for converting a Protobuf message view to a struct.
-pub trait FromProto: Sized {
-    type Proto: protobuf::AsView;
-    type Context;
+pub trait FromProto<Context = ()>: Sized {
+    type Proto;
 
     fn from_proto(
         proto: impl protobuf::AsView<Proxied = Self::Proto>,
-        ctx: &Self::Context,
+        ctx: Context,
     ) -> Result<Self, StatusError>;
 }