From 1e2ea824fd50d21fe2c52532e422821508415317 Mon Sep 17 00:00:00 2001
From: arnaucube <git@arnaucube.com>
Date: Wed, 16 Jul 2025 18:57:32 +0200
Subject: [PATCH] implement GLev encryption & decryption

---
 gfhe/src/glev.rs | 91 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 gfhe/src/glev.rs

diff --git a/gfhe/src/glev.rs b/gfhe/src/glev.rs
new file mode 100644
index 0000000..8337c1b
--- /dev/null
+++ b/gfhe/src/glev.rs
@@ -0,0 +1,91 @@
+use anyhow::Result;
+use rand::Rng;
+use rand_distr::{Normal, Uniform};
+use std::ops::{Add, Mul};
+
+use arith::{Ring, Rq, TR};
+
+use crate::glwe::{PublicKey, SecretKey, GLWE};
+
+const ERR_SIGMA: f64 = 3.2;
+
+// l GLWEs
+#[derive(Clone, Debug)]
+pub struct GLev<const Q: u64, const N: usize, const K: usize>(pub(crate) Vec<GLWE<Q, N, K>>);
+
+impl<const Q: u64, const N: usize, const K: usize> GLev<Q, N, K> {
+    pub fn encrypt(
+        mut rng: impl Rng,
+        beta: u32,
+        l: u32,
+        pk: &PublicKey<Q, N, K>,
+        m: &Rq<Q, N>,
+        // delta: u64,
+    ) -> Result<Self> {
+        let glev: Vec<GLWE<Q, N, K>> = (0..l)
+            .map(|i| {
+                GLWE::<Q, N, K>::encrypt(&mut rng, pk, &(*m * (Q / beta.pow(i as u32) as u64)), 1)
+            })
+            .collect::<Result<Vec<_>>>()?;
+
+        Ok(Self(glev))
+    }
+    pub fn encrypt_s(
+        mut rng: impl Rng,
+        beta: u32,
+        l: u32,
+        sk: &SecretKey<Q, N, K>,
+        m: &Rq<Q, N>,
+        // delta: u64,
+    ) -> Result<Self> {
+        let glev: Vec<GLWE<Q, N, K>> = (0..l)
+            .map(|i| {
+                GLWE::<Q, N, K>::encrypt_s(&mut rng, sk, &(*m * (Q / beta.pow(i as u32) as u64)), 1)
+            })
+            .collect::<Result<Vec<_>>>()?;
+
+        Ok(Self(glev))
+    }
+
+    pub fn decrypt<const T: u64>(&self, sk: &SecretKey<Q, N, K>, delta: u64) -> Rq<Q, N> {
+        self.0[1].decrypt::<T>(sk, delta)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use anyhow::Result;
+    use rand::distributions::Uniform;
+
+    use super::*;
+
+    #[test]
+    fn test_encrypt_decrypt() -> Result<()> {
+        const Q: u64 = 2u64.pow(16) + 1;
+        const N: usize = 128;
+        const T: u64 = 2; // plaintext modulus
+        const K: usize = 16;
+        type S = GLev<Q, N, K>;
+
+        let beta: u32 = 2;
+        let l: u32 = 16;
+
+        let delta: u64 = Q / T; // floored
+        let mut rng = rand::thread_rng();
+
+        for _ in 0..200 {
+            let (sk, pk) = GLWE::<Q, N, K>::new_key(&mut rng)?;
+
+            let msg_dist = Uniform::new(0_u64, T);
+            let m = Rq::<T, N>::rand_u64(&mut rng, msg_dist)?;
+            let m: Rq<Q, N> = m.remodule::<Q>();
+
+            let c = S::encrypt(&mut rng, beta, l, &pk, &m)?;
+            let m_recovered = c.decrypt::<T>(&sk, delta);
+
+            assert_eq!(m.remodule::<T>(), m_recovered.remodule::<T>());
+        }
+
+        Ok(())
+    }
+}