diff --git a/src/protocol/arena.rs b/src/protocol/arena.rs
new file mode 100644
index 0000000000000000000000000000000000000000..e83360611516969e9e1e97dfff8898cea39fb9a3
--- /dev/null
+++ b/src/protocol/arena.rs
@@ -0,0 +1,57 @@
+use core::hash::Hash;
+use core::marker::PhantomData;
+
+#[derive(Debug, serde::Serialize)]
+pub struct Id<T> {
+    index: u32,
+    _phantom: PhantomData<T>,
+}
+impl<T> Clone for Id<T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+impl<T> Copy for Id<T> {}
+impl<T> PartialEq for Id<T> {
+    fn eq(&self, other: &Self) -> bool {
+        self.index.eq(&other.index)
+    }
+}
+impl<T> Eq for Id<T> {}
+impl<T> Hash for Id<T> {
+    fn hash<H: std::hash::Hasher>(&self, h: &mut H) {
+        self.index.hash(h);
+    }
+}
+
+pub struct Arena<T> {
+    store: Vec<T>,
+}
+impl<T> Arena<T> {
+    pub fn new() -> Self {
+        Self { store: vec![] }
+    }
+    pub fn alloc_with_id(&mut self, f: impl FnOnce(Id<T>) -> T) -> Id<T> {
+        use std::convert::TryFrom;
+        let id = Id {
+            index: u32::try_from(self.store.len()).expect("Out of capacity!"),
+            _phantom: Default::default(),
+        };
+        self.store.push(f(id));
+        id
+    }
+    pub fn iter(&self) -> impl Iterator<Item = (Id<T>, &T)> {
+        (0..).map(|index| Id { index, _phantom: Default::default() }).zip(self.store.iter())
+    }
+}
+impl<T> core::ops::Index<Id<T>> for Arena<T> {
+    type Output = T;
+    fn index(&self, id: Id<T>) -> &Self::Output {
+        self.store.index(id.index as usize)
+    }
+}
+impl<T> core::ops::IndexMut<Id<T>> for Arena<T> {
+    fn index_mut(&mut self, id: Id<T>) -> &mut Self::Output {
+        self.store.index_mut(id.index as usize)
+    }
+}