From d5dc9e690201ef58e2e1bbe413d3fd69d25d59f3 Mon Sep 17 00:00:00 2001
From: Jean-Philippe Bossuat <jeanphilippe.bossuat@gmail.com>
Date: Thu, 12 Jun 2025 10:54:23 +0200
Subject: [PATCH] Fixed block binary secret generation & added CGGI blind
 rotation key generation

---
 backend/src/scalar_znx.rs       | 12 ++++---
 core/src/blind_rotation/ccgi.rs |  0
 core/src/blind_rotation/key.rs  | 60 +++++++++++++++++++++++++++++++++
 core/src/blind_rotation/mod.rs  |  2 ++
 core/src/lib.rs                 |  1 +
 5 files changed, 71 insertions(+), 4 deletions(-)
 create mode 100644 core/src/blind_rotation/ccgi.rs
 create mode 100644 core/src/blind_rotation/key.rs
 create mode 100644 core/src/blind_rotation/mod.rs

diff --git a/backend/src/scalar_znx.rs b/backend/src/scalar_znx.rs
index 4c45f36..e252a9b 100644
--- a/backend/src/scalar_znx.rs
+++ b/backend/src/scalar_znx.rs
@@ -91,10 +91,14 @@ impl<D: AsMut<[u8]> + AsRef<[u8]>> ScalarZnx<D> {
     }
 
     pub fn fill_binary_block(&mut self, col: usize, block_size: usize, source: &mut Source) {
-        assert!(self.n() % block_size == 0);
-        for chunk in self.at_mut(col, 0).chunks_mut(block_size) {
-            chunk[0] = 1;
-            chunk.shuffle(source);
+        assert!(block_size & (block_size - 1) == 0);
+        let max_idx: u64 = (block_size + 1) as u64;
+        let mask_idx: u64 = (2 * block_size - 1) as u64;
+        for block in self.at_mut(col, 0).chunks_mut(block_size) {
+            let idx: usize = source.next_u64n(max_idx, mask_idx) as usize;
+            if idx != block_size {
+                block[idx] = 1;
+            }
         }
     }
 }
diff --git a/core/src/blind_rotation/ccgi.rs b/core/src/blind_rotation/ccgi.rs
new file mode 100644
index 0000000..e69de29
diff --git a/core/src/blind_rotation/key.rs b/core/src/blind_rotation/key.rs
new file mode 100644
index 0000000..4076e14
--- /dev/null
+++ b/core/src/blind_rotation/key.rs
@@ -0,0 +1,60 @@
+use backend::{Backend, FFT64, Module, ScalarZnx, ScalarZnxAlloc, ScalarZnxToRef, Scratch, ZnxView, ZnxViewMut};
+use sampling::source::Source;
+
+use crate::{AutomorphismKey, GGSWCiphertext, GLWESecret, SecretDistribution};
+
+pub struct BlindRotationKeyCGGI<B: Backend> {
+    pub(crate) data: Vec<GGSWCiphertext<Vec<u8>, B>>,
+    pub(crate) dist: SecretDistribution,
+}
+
+pub struct BlindRotationKeyFHEW<B: Backend> {
+    pub(crate) data: Vec<GGSWCiphertext<Vec<u8>, B>>,
+    pub(crate) auto: Vec<AutomorphismKey<Vec<u8>, B>>,
+}
+
+impl BlindRotationKeyCGGI<FFT64> {
+    pub fn allocate(module: &Module<FFT64>, lwe_degree: usize, basek: usize, k: usize, rows: usize, rank: usize) -> Self {
+        let mut data: Vec<GGSWCiphertext<Vec<u8>, FFT64>> = Vec::with_capacity(lwe_degree);
+        (0..lwe_degree).for_each(|_| data.push(GGSWCiphertext::alloc(module, basek, k, rows, 1, rank)));
+        Self {
+            data,
+            dist: SecretDistribution::NONE,
+        }
+    }
+
+    pub fn generate_from_sk<DataSkGLWE, DataSkLWE>(
+        &mut self,
+        module: &Module<FFT64>,
+        sk_glwe: &GLWESecret<DataSkGLWE, FFT64>,
+        sk_lwe: &GLWESecret<DataSkLWE, FFT64>,
+        source_xa: &mut Source,
+        source_xe: &mut Source,
+        sigma: f64,
+        scratch: &mut Scratch,
+    ) where
+        DataSkGLWE: AsRef<[u8]>,
+        DataSkLWE: AsRef<[u8]>,
+    {
+        #[cfg(debug_assertions)]
+        {
+            assert_eq!(self.data.len(), sk_lwe.n());
+            assert_eq!(sk_glwe.n(), module.n());
+            assert_eq!(sk_glwe.rank(), self.data[0].rank());
+            match sk_lwe.dist {
+                SecretDistribution::BinaryBlock(_) | SecretDistribution::BinaryFixed(_) | SecretDistribution::BinaryProb(_) => {}
+                _ => panic!("invalid GLWESecret distribution: must be BinaryBlock, BinaryFixed or BinaryProb"),
+            }
+        }
+
+        self.dist = sk_lwe.dist;
+
+        let mut pt: ScalarZnx<Vec<u8>> = module.new_scalar_znx(1);
+        let sk_ref: ScalarZnx<&[u8]> = sk_lwe.data.to_ref();
+
+        self.data.iter_mut().enumerate().for_each(|(i, ggsw)| {
+            pt.at_mut(0, 0)[0] = sk_ref.at(0, 0)[i];
+            ggsw.encrypt_sk(module, &pt, sk_glwe, source_xa, source_xe, sigma, scratch);
+        })
+    }
+}
diff --git a/core/src/blind_rotation/mod.rs b/core/src/blind_rotation/mod.rs
new file mode 100644
index 0000000..c531781
--- /dev/null
+++ b/core/src/blind_rotation/mod.rs
@@ -0,0 +1,2 @@
+// pub mod cggi;
+pub mod key;
diff --git a/core/src/lib.rs b/core/src/lib.rs
index 69eb045..3aa05ea 100644
--- a/core/src/lib.rs
+++ b/core/src/lib.rs
@@ -1,4 +1,5 @@
 pub mod automorphism;
+pub mod blind_rotation;
 pub mod elem;
 pub mod gglwe_ciphertext;
 pub mod ggsw_ciphertext;