From 2e0e7e11b43bd488afe7833e070ab1812a1b831e Mon Sep 17 00:00:00 2001
From: Jean-Philippe Bossuat <jeanphilippe.bossuat@gmail.com>
Date: Tue, 8 Jul 2025 13:54:20 +0200
Subject: [PATCH] Enforce extension factor to be a power of two

---
 core/src/blind_rotation/ccgi.rs | 1 -
 core/src/blind_rotation/lut.rs  | 8 ++++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/core/src/blind_rotation/ccgi.rs b/core/src/blind_rotation/ccgi.rs
index 62ec4ac..3e0dc33 100644
--- a/core/src/blind_rotation/ccgi.rs
+++ b/core/src/blind_rotation/ccgi.rs
@@ -82,7 +82,6 @@ pub fn cggi_blind_rotate<DataRes, DataIn>(
     }
 }
 
-// TODO: ENSURE DOMAIN EXTENSION AS
 pub(crate) fn cggi_blind_rotate_block_binary_extended<DataRes, DataIn>(
     module: &Module<FFT64>,
     res: &mut GLWECiphertext<DataRes>,
diff --git a/core/src/blind_rotation/lut.rs b/core/src/blind_rotation/lut.rs
index a7fe003..96c1422 100644
--- a/core/src/blind_rotation/lut.rs
+++ b/core/src/blind_rotation/lut.rs
@@ -8,6 +8,14 @@ pub struct LookUpTable {
 
 impl LookUpTable {
     pub fn alloc(module: &Module<FFT64>, basek: usize, k: usize, extension_factor: usize) -> Self {
+        #[cfg(debug_assertions)]
+        {
+            assert!(
+                extension_factor & (extension_factor - 1) == 0,
+                "extension_factor must be a power of two but is: {}",
+                extension_factor
+            );
+        }
         let size: usize = k.div_ceil(basek);
         let mut data: Vec<VecZnx<Vec<u8>>> = Vec::with_capacity(extension_factor);
         (0..extension_factor).for_each(|_| {