diff --git a/wallet-core/src/ffi.rs b/wallet-core/src/ffi.rs
index 86f64775fb..0e4a528f57 100644
--- a/wallet-core/src/ffi.rs
+++ b/wallet-core/src/ffi.rs
@@ -33,12 +33,20 @@ use core::{ptr, slice};
 use dusk_bytes::Serializable;
 use execution_core::{
     signatures::bls::PublicKey as BlsPublicKey,
-    transfer::phoenix::{NoteLeaf, PublicKey as PhoenixPublicKey},
+    transfer::phoenix::{
+        ArchivedNoteLeaf, NoteLeaf, PublicKey as PhoenixPublicKey,
+    },
+    BlsScalar,
 };
 use zeroize::Zeroize;
 
 use rkyv::to_bytes;
 
+#[no_mangle]
+static KEY_SIZE: usize = BlsScalar::SIZE;
+#[no_mangle]
+static ITEM_SIZE: usize = core::mem::size_of::<ArchivedNoteLeaf>();
+
 /// The size of the scratch buffer used for parsing the notes.
 const NOTES_BUFFER_SIZE: usize = 96 * 1024;
 
@@ -89,10 +97,23 @@ pub unsafe fn map_owned(
     indexes: *const u8,
     notes_ptr: *const u8,
     owned_ptr: *mut *mut u8,
+    last_info_ptr: *mut [u8; 16],
 ) -> ErrorCode {
+    use core::cmp::max;
+
     let keys = indexes_into_keys(seed, indexes, derive_phoenix_sk);
     let notes: Vec<NoteLeaf> = mem::from_buffer(notes_ptr)?;
 
+    let (block_height, pos) =
+        notes
+            .iter()
+            .fold((0u64, 0u64), |(block_height, pos), leaf| {
+                (
+                    max(block_height, leaf.block_height),
+                    max(pos, *leaf.note.pos()),
+                )
+            });
+
     let owned = notes::owned::map(&keys, notes);
 
     keys.into_iter().for_each(|mut sk| sk.zeroize());
@@ -110,6 +131,16 @@ pub unsafe fn map_owned(
 
     ptr::copy_nonoverlapping(len.as_ptr(), ptr, 4);
     ptr::copy_nonoverlapping(bytes.as_ptr(), ptr.add(4), bytes.len());
+    ptr::copy_nonoverlapping(
+        block_height.to_le_bytes().as_ptr(),
+        &mut (*last_info_ptr)[0],
+        8,
+    );
+    ptr::copy_nonoverlapping(
+        pos.to_le_bytes().as_ptr(),
+        &mut (*last_info_ptr)[8],
+        8,
+    );
 
     ErrorCode::Ok
 }
diff --git a/wallet-core/src/notes/balance.rs b/wallet-core/src/notes/balance.rs
index 2e05111004..5a4f345b16 100644
--- a/wallet-core/src/notes/balance.rs
+++ b/wallet-core/src/notes/balance.rs
@@ -19,6 +19,33 @@ pub fn calculate<T>(
     vk: &PhoenixViewKey,
     notes: impl Iterator<Item = T>,
 ) -> TotalAmount
+where
+    T: AsRef<Note>,
+{
+    let mut values: Vec<u64> = notes
+        .filter_map(|note| {
+            vk.owns(note.as_ref().stealth_address())
+                .then_some(true)
+                .and(note.as_ref().value(Some(vk)).ok())
+        })
+        .collect();
+
+    values.sort_by(|a, b| b.cmp(a));
+
+    let spendable = values.iter().take(MAX_INPUT_NOTES).sum();
+    let value = spendable + values.iter().skip(MAX_INPUT_NOTES).sum::<u64>();
+
+    TotalAmount { value, spendable }
+}
+
+/// Calculate the sum for all the given [`Note`]s without
+/// performing any ownership checks. The [`PhoenixViewKey`]
+/// is used solely for decrypting the values of obfuscated
+/// notes.
+pub fn calculate_unchecked<T>(
+    vk: &PhoenixViewKey,
+    notes: impl Iterator<Item = T>,
+) -> TotalAmount
 where
     T: AsRef<Note>,
 {