diff --git a/src/core/api.rs b/src/core/api.rs
index 8db3b307..895a5c9b 100644
--- a/src/core/api.rs
+++ b/src/core/api.rs
@@ -81,12 +81,14 @@ impl Covercrypt {
         policy: &Policy,
         msk: &mut MasterSecretKey,
         mpk: &mut MasterPublicKey,
+        keep_old_subkeys: bool,
     ) -> Result<(), Error> {
         rekey(
             &mut *self.rng.lock().expect("Mutex lock failed!"),
             msk,
             mpk,
             &policy.access_policy_to_partitions(access_policy, false)?,
+            keep_old_subkeys,
         )
     }
 
diff --git a/src/core/primitives.rs b/src/core/primitives.rs
index a17cf2b6..f80fd907 100644
--- a/src/core/primitives.rs
+++ b/src/core/primitives.rs
@@ -221,7 +221,9 @@ pub fn keygen(
         let subkey = msk
             .subkeys
             .get_current_revision(partition)
-            .ok_or(Error::KeyError("Missing master subkey".to_string()))?;
+            .ok_or(Error::KeyError(
+                "Master secret key and Policy are not in sync.".to_string(),
+            ))?;
         subkeys.create_chain_with_single_value(partition.clone(), subkey.clone());
         Ok::<_, Error>(())
     })?;
@@ -404,10 +406,11 @@ pub fn rekey(
     msk: &mut MasterSecretKey,
     mpk: &mut MasterPublicKey,
     partitions_to_rotate: &HashSet<Partition>,
+    keep_old_subkeys: bool,
 ) -> Result<(), Error> {
     let h = R25519PublicKey::from(&msk.s);
     for partition in partitions_to_rotate {
-        // write a `get_encryption`` function in a dedicated SecretSubkey struct?
+        // write a `get_encryption` function in a dedicated SecretSubkey struct?
         let is_hybridized = EncryptionHint::new(
             msk.subkeys
                 .get_current_revision(partition)
@@ -416,6 +419,10 @@ pub fn rekey(
         );
         let (public_subkey, secret_subkey) = create_subkey_pair(rng, &h, is_hybridized);
         msk.subkeys.insert(partition.clone(), secret_subkey);
+        if !keep_old_subkeys {
+            // remove all older keys for a given partition
+            msk.subkeys.pop_tail(partition);
+        }
 
         // update public subkey if partition is not read only
         if mpk.subkeys.contains_key(partition) {
@@ -447,20 +454,19 @@ pub fn refresh(
     usk.subkeys.retain_keys(msk.subkeys.keys().collect());
 
     for (partition, user_chain) in usk.subkeys.iter_mut() {
-        let mut master_chain = msk.subkeys.iter_chain(partition);
+        let mut master_chain = msk.subkeys.iter_chain(partition).expect("at least one key");
 
         // Remove all but the most recent subkey for this partition
         if !keep_old_rights {
             // find the most recent subkey between the master and user key
-            let master_first_key = master_chain.next().expect("have one key");
+            let master_first_key = master_chain.next().expect("at least one key");
             if Some(master_first_key) != user_chain.head.as_ref().map(|item| &item.data) {
                 // new key
                 let new_element = Box::new(Element::new(master_first_key.clone()));
                 user_chain.head.replace(new_element);
             }
             // remove older keys if any and update length
-            let _ = user_chain.head.as_mut().expect("have one key").next.take();
-            user_chain.length = 1;
+            user_chain.pop_tail();
             // skip to next partition
             continue;
         }
diff --git a/src/data_struct/revision_map.rs b/src/data_struct/revision_map.rs
index e1f5a572..7e439df5 100644
--- a/src/data_struct/revision_map.rs
+++ b/src/data_struct/revision_map.rs
@@ -6,7 +6,6 @@ use std::{
     },
     fmt::Debug,
     hash::Hash,
-    iter,
 };
 
 /// a `VersionedMap` stores linked lists.
@@ -17,7 +16,6 @@ where
     V: Debug,
 {
     pub(crate) map: HashMap<K, LinkedList<V>>,
-    length: usize,
 }
 
 impl<K, V> RevisionMap<K, V>
@@ -28,23 +26,21 @@ where
     pub fn new() -> Self {
         Self {
             map: HashMap::new(),
-            length: 0,
         }
     }
 
     pub fn with_capacity(capacity: usize) -> Self {
         Self {
             map: HashMap::with_capacity(capacity),
-            length: 0,
         }
     }
 
     pub fn len(&self) -> usize {
-        self.length
+        self.map.values().map(|chain| chain.len()).sum()
     }
 
     pub fn is_empty(&self) -> bool {
-        self.length == 0
+        self.len() == 0
     }
 
     pub fn nb_chains(&self) -> usize {
@@ -68,9 +64,6 @@ where
 
     /// Inserts value at the front of the chain for a given key
     pub fn insert(&mut self, key: K, value: V) {
-        // All branches will add an element in the map.
-        self.length += 1;
-
         match self.map.entry(key) {
             Entry::Occupied(entry) => Self::insert_in_chain(entry, value),
             Entry::Vacant(entry) => Self::insert_new_chain(entry, value),
@@ -113,51 +106,32 @@ where
 
     /// Iterates through all revisions of a given key starting with the more
     /// recent one.
-    pub fn iter_chain<'a, Q>(&'a self, key: &Q) -> Box<dyn 'a + Iterator<Item = &V>>
+    pub fn iter_chain<Q>(&self, key: &Q) -> Option<impl Iterator<Item = &V>>
     where
         K: Borrow<Q>,
         Q: Hash + Eq + ?Sized,
     {
-        match self.map.get(key) {
-            Some(chain) => Box::new(chain.iter()),
-            None => Box::new(iter::empty()),
-        }
+        self.map.get(key).map(LinkedList::iter)
     }
 
     /// Removes and returns an iterator over all revisions from a given key.
-    pub fn remove_chain<'a, Q>(&'a mut self, key: &Q) -> Box<dyn 'a + Iterator<Item = V>>
+    pub fn remove_chain<Q>(&mut self, key: &Q) -> Option<impl Iterator<Item = V>>
     where
         K: Borrow<Q>,
         Q: Hash + Eq + ?Sized,
     {
-        match self.map.remove(key) {
-            Some(chain) => {
-                self.length -= chain.len();
-                Box::new(chain.into_iter())
-            }
-            None => Box::new(iter::empty()),
-        }
+        self.map.remove(key).map(LinkedList::into_iter)
     }
 
-    /// Removes and returns the older revision from a given key.
-    pub fn remove_older_revision(&mut self, key: &K) -> Option<V> {
-        let Entry::Occupied(mut entry) = self.map.entry(key.clone()) else {
-            return None;
-        };
-        let chain = entry.get_mut();
-        let removed_entry = chain.pop_back();
-
-        // remove linked list if the last revision was removed
-        if chain.is_empty() {
-            entry.remove_entry();
-        }
-
-        // update map length
-        if removed_entry.is_some() {
-            self.length -= 1;
-        }
-
-        removed_entry
+    /// Removes and returns the older revisions from a given key.
+    pub fn pop_tail<Q>(&mut self, key: &Q) -> Option<impl Iterator<Item = V>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self.map
+            .get_mut(key)
+            .map(|chain| chain.split_off(1).into_iter())
     }
 
     pub fn retain_keys(&mut self, keys: HashSet<&K>) {
@@ -182,42 +156,48 @@ mod tests {
         assert!(map.is_empty());
 
         // Insertions
-        map.insert("Part1".to_string(), "Rotation1".to_string());
+        map.insert("Part1".to_string(), "Part1V1".to_string());
         assert_eq!(map.map.len(), 1);
-        map.insert("Part1".to_string(), "Rotation2".to_string());
+        map.insert("Part1".to_string(), "Part1V2".to_string());
         assert_eq!(map.len(), 2);
         // the inner map only has 1 entry with 2 revisions
         assert_eq!(map.map.len(), 1);
 
-        map.insert("Part2".to_string(), "New".to_string());
+        map.insert("Part2".to_string(), "Part2V1".to_string());
+        map.insert("Part2".to_string(), "Part2V2".to_string());
+        map.insert("Part2".to_string(), "Part2V3".to_string());
         assert_eq!(map.map.len(), 2);
+        assert_eq!(map.len(), 5);
 
         // Get
-        assert_eq!(map.get_current_revision("Part1").unwrap(), "Rotation2");
-        assert_eq!(map.get_current_revision("Part2").unwrap(), "New");
+        assert_eq!(map.get_current_revision("Part1").unwrap(), "Part1V2");
+        assert_eq!(map.get_current_revision("Part2").unwrap(), "Part2V3");
         assert!(map.get_current_revision("Missing").is_none());
 
         // Iterators
         let vec: Vec<_> = map.iter().collect();
-        assert_eq!(vec.len(), 3);
+        assert_eq!(vec.len(), map.len());
 
-        let vec: Vec<_> = map.iter_chain("Part1").collect();
-        assert_eq!(vec, vec!["Rotation2", "Rotation1"]);
+        let vec: Vec<_> = map.iter_chain("Part1").unwrap().collect();
+        assert_eq!(vec, vec!["Part1V2", "Part1V1"]);
 
         let keys_set = map.keys().collect::<HashSet<_>>();
         assert!(keys_set.contains(&"Part1".to_string()));
         assert!(keys_set.contains(&"Part2".to_string()));
 
         // Remove values
-        assert_eq!(
-            map.remove_older_revision(&"Part2".to_string()).unwrap(),
-            "New"
-        );
-        assert_eq!(map.len(), 2);
+        let vec: Vec<_> = map.remove_chain("Part1").unwrap().collect();
+        assert_eq!(vec, vec!["Part1V2".to_string(), "Part1V1".to_string()]);
+        assert_eq!(map.len(), 3);
         assert_eq!(map.map.len(), 1);
 
-        let vec: Vec<_> = map.remove_chain("Part1").collect();
-        assert_eq!(vec, vec!["Rotation2".to_string(), "Rotation1".to_string()]);
+        // Pop tail
+        let vec: Vec<_> = map.pop_tail("Part2").unwrap().collect();
+        assert_eq!(vec, vec!["Part2V2".to_string(), "Part2V1".to_string()]);
+        assert_eq!(map.len(), 1);
+        let vec: Vec<_> = map.remove_chain("Part2").unwrap().collect();
+        assert_eq!(vec, vec!["Part2V3".to_string()]);
+
         assert!(map.is_empty());
     }
 }
diff --git a/src/data_struct/revision_vec.rs b/src/data_struct/revision_vec.rs
index 66dcf96e..d31f4a5d 100644
--- a/src/data_struct/revision_vec.rs
+++ b/src/data_struct/revision_vec.rs
@@ -20,26 +20,21 @@ use std::{
 #[derive(Default, Debug, PartialEq, Eq)]
 pub struct RevisionVec<K, T> {
     chains: Vec<(K, RevisionList<T>)>,
-    length: usize,
 }
 
 impl<K, T> RevisionVec<K, T> {
     pub fn new() -> Self {
-        Self {
-            chains: Vec::new(),
-            length: 0,
-        }
+        Self { chains: Vec::new() }
     }
 
     pub fn with_capacity(capacity: usize) -> Self {
         Self {
             chains: Vec::with_capacity(capacity),
-            length: 0,
         }
     }
 
     pub fn len(&self) -> usize {
-        self.length
+        self.chains.iter().map(|(_, chain)| chain.len()).sum()
     }
 
     pub fn is_empty(&self) -> bool {
@@ -56,7 +51,6 @@ impl<K, T> RevisionVec<K, T> {
     pub fn create_chain_with_single_value(&mut self, key: K, val: T) {
         let mut new_chain = RevisionList::new();
         new_chain.push_front(val);
-        self.length += 1;
         self.chains.push((key, new_chain));
     }
 
@@ -65,14 +59,12 @@ impl<K, T> RevisionVec<K, T> {
     /// structure.
     pub fn insert_new_chain(&mut self, key: K, new_chain: RevisionList<T>) {
         if !new_chain.is_empty() {
-            self.length += new_chain.len();
             self.chains.push((key, new_chain));
         }
     }
 
     pub fn clear(&mut self) {
         self.chains.clear();
-        self.length = self.chains.len();
     }
 
     pub fn retain_keys(&mut self, keys: HashSet<&K>)
@@ -190,6 +182,18 @@ impl<T> RevisionList<T> {
         self.head.as_ref().map(|element| &element.data)
     }
 
+    pub fn pop_tail(&mut self) -> RevisionListIter<T> {
+        self.length = self.head.as_ref().map_or(0, |_| 1);
+        match &self.head {
+            Some(head) => RevisionListIter {
+                current_element: &head.next,
+            },
+            None => RevisionListIter {
+                current_element: &None,
+            },
+        }
+    }
+
     pub fn iter(&self) -> impl Iterator<Item = &T> {
         RevisionListIter::new(self)
     }