diff --git a/src/channel/mod.rs b/src/channel/mod.rs
index df11db1..4f3e007 100644
--- a/src/channel/mod.rs
+++ b/src/channel/mod.rs
@@ -1,5 +1,50 @@
 use ark_ff::Field;
 
+#[derive(Default)]
+struct Annotation {
+    scope: Vec<String>,
+    annotations: Vec<String>,
+    annotations_enabled: bool,
+    extra_annotations_enabled: bool,
+    prover_to_verifier_bytes: usize,
+    expected_annotations: Option<Vec<String>>,
+    annotation_prefix: String,
+}
+
+impl Annotation {
+    /// Call this function every time that the annotation scope is updated to recalculate the prefix to
+    /// be added to annotations. It takes all annotation scopes in the annotation_scope_ vector and
+    /// concatenates them with "/" delimiters.
+    fn update_annotation_prefix(&mut self) {
+        self.annotation_prefix = self
+            .scope
+            .iter()
+            .fold(String::new(), |acc, s| acc + "/" + s)
+            + ": ";
+    }
+
+    fn add_annotation(&mut self, annotation: String) {
+        if self.annotations_enabled {
+            self.annotations.push(annotation);
+        }
+    }
+
+    fn annotate_prover_to_verifier(&mut self, annotation: String, n_bytes: usize) {
+        let start = self.prover_to_verifier_bytes;
+        self.prover_to_verifier_bytes += n_bytes;
+        let end = self.prover_to_verifier_bytes;
+
+        self.add_annotation(format!(
+            "P->V[{}:{}]: {}{}\n",
+            start, end, self.annotation_prefix, annotation
+        ));
+    }
+
+    fn annotate_verifier_to_prover(&mut self, annotation: String) {
+        self.add_annotation(format!("V->P: {}{}\n", self.annotation_prefix, annotation));
+    }
+}
+
 #[allow(dead_code)]
 trait Channel {
     type Field: Field;
@@ -11,4 +56,26 @@ trait Channel {
     fn random_number(&mut self, bound: u64) -> u64;
 
     fn random_field(&mut self) -> Self::Field;
+
+    fn apply_proof_of_work(&mut self, security_bits: usize);
+
+    fn begin_query_phase(&mut self);
+
+    fn enter_annotation_scope(&mut self, scope: String);
+    fn exit_annotation_scope(&mut self);
+    fn disable_annotations(&mut self);
+    fn disable_extra_annotations(&mut self);
+    fn extra_annotations_disabled(&self) -> bool;
+    fn set_expected_annotations(&mut self, expected_annotations: Vec<String>);
+
+    fn get_annotations(&self) -> &Vec<String>;
+    fn get_annotations_mut(&mut self) -> &mut Annotation;
+
+    fn annotate_prover_to_verifier(&mut self, annotation: String, n_bytes: usize) {
+        self.get_annotations_mut().annotate_prover_to_verifier(annotation, n_bytes);
+    }
+
+    fn annotate_verifier_to_prover(&mut self, annotation: String) {
+        self.get_annotations_mut().annotate_verifier_to_prover(annotation)
+    }
 }