diff --git a/src/backend/discovery.rs b/src/backend/discovery.rs
new file mode 100644
index 0000000..4a395f8
--- /dev/null
+++ b/src/backend/discovery.rs
@@ -0,0 +1,18 @@
+use anyhow::Error;
+
+use crate::{messages::discovery::DiscoveryMessage, model::repository::Repository};
+
+use super::DiscoveryBackend;
+
+pub struct GiteratedDiscoveryProtocol {}
+
+#[async_trait::async_trait]
+impl DiscoveryBackend for GiteratedDiscoveryProtocol {
+    async fn try_handle(&mut self, request: DiscoveryMessage) -> Result<bool, Error> {
+        todo!()
+    }
+
+    async fn search(&mut self, search: &str) -> Result<Vec<Repository>, Error> {
+        todo!()
+    }
+}
diff --git a/src/backend/mod.rs b/src/backend/mod.rs
index 0e13756..0d71899 100644
--- a/src/backend/mod.rs
+++ b/src/backend/mod.rs
@@ -1,3 +1,4 @@
+pub mod discovery;
 pub mod git;
 pub mod github;
 pub mod user;
@@ -11,6 +12,7 @@ use crate::{
             AuthenticationTokenRequest, AuthenticationTokenResponse, RegisterAccountRequest,
             RegisterAccountResponse,
         },
+        discovery::DiscoveryMessage,
         repository::{
             CreateRepositoryRequest, CreateRepositoryResponse, RepositoryFileInspectRequest,
             RepositoryFileInspectionResponse, RepositoryInfoRequest, RepositoryIssueLabelsRequest,
@@ -23,7 +25,7 @@ use crate::{
         },
         ValidatedUserAuthenticated,
     },
-    model::repository::RepositoryView,
+    model::repository::{Repository, RepositoryView},
 };
 
 #[async_trait]
@@ -84,3 +86,9 @@ pub trait UserBackend: AuthBackend {
 
     async fn bio(&mut self, request: UserBioRequest) -> Result<UserBioResponse, Error>;
 }
+
+#[async_trait::async_trait]
+pub trait DiscoveryBackend {
+    async fn try_handle(&mut self, request: DiscoveryMessage) -> Result<bool, Error>;
+    async fn search(&mut self, search: &str) -> Result<Vec<Repository>, Error>;
+}
diff --git a/src/messages/discovery.rs b/src/messages/discovery.rs
new file mode 100644
index 0000000..a94df28
--- /dev/null
+++ b/src/messages/discovery.rs
@@ -0,0 +1,35 @@
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+
+use crate::model::discovery::DiscoveryItem;
+
+use super::InstanceAuthenticated;
+
+#[derive(Hash, PartialEq, Eq, Debug, Serialize, Deserialize)]
+pub struct DiscoveryMessage {
+    pub message: InstanceAuthenticated<DiscoveryMessageKind>,
+}
+
+#[derive(Hash, PartialEq, Eq, Debug, Serialize, Deserialize)]
+pub enum DiscoveryMessageKind {
+    Offer(DiscoveryOffer),
+    Request(DiscoveryRequest),
+    Discoveries(Discoveries),
+}
+
+#[derive(Hash, PartialEq, Eq, Debug, Serialize, Deserialize)]
+pub struct DiscoveryOffer {
+    pub earliest: DateTime<Utc>,
+    pub hashes: Vec<u128>,
+}
+
+#[derive(Hash, PartialEq, Eq, Debug, Serialize, Deserialize)]
+pub struct DiscoveryRequest {
+    pub since: DateTime<Utc>,
+    pub hashes: Vec<u128>,
+}
+
+#[derive(Hash, PartialEq, Eq, Debug, Serialize, Deserialize)]
+pub struct Discoveries {
+    pub discoveries: Vec<DiscoveryItem>,
+}
diff --git a/src/messages/mod.rs b/src/messages/mod.rs
index a4032cc..673a2d9 100644
--- a/src/messages/mod.rs
+++ b/src/messages/mod.rs
@@ -19,6 +19,7 @@ use crate::{
 use self::{authentication::AuthenticationMessage, repository::RepositoryMessage};
 
 pub mod authentication;
+pub mod discovery;
 pub mod issues;
 pub mod repository;
 pub mod user;
@@ -39,6 +40,30 @@ pub struct InstanceAuthenticated<T: Serialize> {
     signature: Vec<u8>,
 }
 
+impl<T> PartialEq for InstanceAuthenticated<T>
+where
+    T: PartialEq + Serialize,
+{
+    fn eq(&self, other: &Self) -> bool {
+        self.message == other.message
+            && self.instance == other.instance
+            && self.signature == other.signature
+    }
+}
+
+impl<T> Eq for InstanceAuthenticated<T> where T: Eq + Serialize {}
+
+impl<T> std::hash::Hash for InstanceAuthenticated<T>
+where
+    T: std::hash::Hash + Serialize,
+{
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.message.hash(state);
+        self.instance.hash(state);
+        self.signature.hash(state);
+    }
+}
+
 impl<T> Clone for InstanceAuthenticated<T>
 where
     T: Clone + Serialize,
diff --git a/src/model/discovery.rs b/src/model/discovery.rs
new file mode 100644
index 0000000..b29e034
--- /dev/null
+++ b/src/model/discovery.rs
@@ -0,0 +1,15 @@
+use serde::{Deserialize, Serialize};
+
+use crate::model::{instance::Instance, repository::Repository};
+
+#[derive(Hash, PartialEq, Eq, Debug, Serialize, Deserialize)]
+pub enum DiscoveryItem {
+    Instance {
+        instance: Instance,
+        signature: Vec<u8>,
+    },
+    Repository {
+        repository: Repository,
+        signature: Vec<u8>,
+    },
+}
diff --git a/src/model/mod.rs b/src/model/mod.rs
index 9c3fa48..a4d3269 100644
--- a/src/model/mod.rs
+++ b/src/model/mod.rs
@@ -3,6 +3,7 @@
 //! All network data model types that are not directly associated with
 //! individual requests or responses.
 
+pub mod discovery;
 pub mod instance;
 pub mod repository;
 pub mod user;
diff --git a/src/model/repository.rs b/src/model/repository.rs
index 4b9e66e..a68dea3 100644
--- a/src/model/repository.rs
+++ b/src/model/repository.rs
@@ -27,7 +27,7 @@ use super::{instance::Instance, user::User};
 /// // This is correct
 /// assert_eq!(Repository::from_str("barson:giterated.dev/foo@giterated.dev").unwrap(), repository);
 /// ```
-#[derive(Hash, Clone, Serialize, Deserialize)]
+#[derive(Hash, Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
 pub struct Repository {
     pub owner: User,
     pub name: String,