From 752525a1c64740d9cc1960c72d101a7230f597d1 Mon Sep 17 00:00:00 2001
From: arnaucube <git@arnaucube.com>
Date: Mon, 28 Jul 2025 12:14:44 +0000
Subject: [PATCH] add TGLWE logic (pending to abstract it with TLWE to reuse
 part of the impl)

---
 tfhe/src/lib.rs   |   1 +
 tfhe/src/tglwe.rs | 248 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 249 insertions(+)
 create mode 100644 tfhe/src/tglwe.rs

diff --git a/tfhe/src/lib.rs b/tfhe/src/lib.rs
index 784d84e..9db005b 100644
--- a/tfhe/src/lib.rs
+++ b/tfhe/src/lib.rs
@@ -5,6 +5,7 @@
 #![allow(clippy::upper_case_acronyms)]
 #![allow(dead_code)] // TMP
 
+pub mod tglwe;
 pub mod tgsw;
 pub mod tlev;
 pub mod tlwe;
diff --git a/tfhe/src/tglwe.rs b/tfhe/src/tglwe.rs
new file mode 100644
index 0000000..68eacf7
--- /dev/null
+++ b/tfhe/src/tglwe.rs
@@ -0,0 +1,248 @@
+use anyhow::Result;
+use itertools::zip_eq;
+use rand::distributions::Standard;
+use rand::Rng;
+use rand_distr::{Normal, Uniform};
+use std::array;
+use std::iter::Sum;
+use std::ops::{Add, AddAssign, Mul, Sub};
+
+use arith::{Ring, Rq, Tn, T64, TR};
+use gfhe::{glwe, GLWE};
+
+use crate::tlev::TLev;
+
+pub type SecretKey<const N: usize, const K: usize> = glwe::SecretKey<Tn<N>, K>;
+pub type PublicKey<const N: usize, const K: usize> = glwe::PublicKey<Tn<N>, K>;
+
+#[derive(Clone, Debug)]
+pub struct TGLWE<const N: usize, const K: usize>(pub GLWE<Tn<N>, K>);
+
+impl<const N: usize, const K: usize> TGLWE<N, K> {
+    pub fn zero() -> Self {
+        Self(GLWE::<Tn<N>, K>::zero())
+    }
+
+    pub fn new_key(rng: impl Rng) -> Result<(SecretKey<N, K>, PublicKey<N, K>)> {
+        let (sk, pk) = GLWE::new_key(rng)?;
+        // Ok((SecretKey(sk), PublicKey(pk)))
+        Ok((sk, pk))
+    }
+
+    pub fn encode<const P: u64>(m: &Rq<P, N>) -> Tn<N> {
+        let delta = u64::MAX / P; // floored
+        let coeffs = m.coeffs();
+        Tn(array::from_fn(|i| T64(coeffs[i].0 * delta)))
+    }
+    pub fn decode<const P: u64>(p: &Tn<N>) -> Rq<P, N> {
+        let p = p.mul_div_round(P, u64::MAX);
+        Rq::<P, N>::from_vec_u64(p.coeffs().iter().map(|c| c.0).collect())
+    }
+
+    // encrypts with the given SecretKey (instead of PublicKey)
+    pub fn encrypt_s(rng: impl Rng, sk: &SecretKey<N, K>, p: &Tn<N>) -> Result<Self> {
+        let glwe = GLWE::encrypt_s(rng, &sk, p)?;
+        Ok(Self(glwe))
+    }
+    pub fn encrypt(rng: impl Rng, pk: &PublicKey<N, K>, p: &Tn<N>) -> Result<Self> {
+        let glwe = GLWE::encrypt(rng, &pk, p)?;
+        Ok(Self(glwe))
+    }
+    pub fn decrypt(&self, sk: &SecretKey<N, K>) -> Tn<N> {
+        self.0.decrypt(&sk)
+    }
+}
+
+impl<const N: usize, const K: usize> Add<TGLWE<N, K>> for TGLWE<N, K> {
+    type Output = Self;
+    fn add(self, other: Self) -> Self {
+        Self(self.0 + other.0)
+    }
+}
+impl<const N: usize, const K: usize> AddAssign for TGLWE<N, K> {
+    fn add_assign(&mut self, rhs: Self) {
+        self.0 += rhs.0
+    }
+}
+impl<const N: usize, const K: usize> Sum<TGLWE<N, K>> for TGLWE<N, K> {
+    fn sum<I>(iter: I) -> Self
+    where
+        I: Iterator<Item = Self>,
+    {
+        let mut acc = TGLWE::<N, K>::zero();
+        for e in iter {
+            acc += e;
+        }
+        acc
+    }
+}
+
+impl<const N: usize, const K: usize> Sub<TGLWE<N, K>> for TGLWE<N, K> {
+    type Output = Self;
+    fn sub(self, other: Self) -> Self {
+        Self(self.0 - other.0)
+    }
+}
+
+// plaintext addition
+impl<const N: usize, const K: usize> Add<Tn<N>> for TGLWE<N, K> {
+    type Output = Self;
+    fn add(self, plaintext: Tn<N>) -> Self {
+        let a: TR<Tn<N>, K> = self.0 .0;
+        let b: Tn<N> = self.0 .1 + plaintext;
+        Self(GLWE(a, b))
+    }
+}
+// plaintext substraction
+impl<const N: usize, const K: usize> Sub<Tn<N>> for TGLWE<N, K> {
+    type Output = Self;
+    fn sub(self, plaintext: Tn<N>) -> Self {
+        let a: TR<Tn<N>, K> = self.0 .0;
+        let b: Tn<N> = self.0 .1 - plaintext;
+        Self(GLWE(a, b))
+    }
+}
+// plaintext multiplication
+impl<const N: usize, const K: usize> Mul<Tn<N>> for TGLWE<N, K> {
+    type Output = Self;
+    fn mul(self, plaintext: Tn<N>) -> Self {
+        let a: TR<Tn<N>, K> = TR(self.0 .0 .0.iter().map(|r_i| *r_i * plaintext).collect());
+        let b: Tn<N> = self.0 .1 * plaintext;
+        Self(GLWE(a, b))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use anyhow::Result;
+    use rand::distributions::Uniform;
+
+    use super::*;
+
+    #[test]
+    fn test_encrypt_decrypt() -> Result<()> {
+        const T: u64 = 128; // msg space (msg modulus)
+        const N: usize = 64;
+        const K: usize = 16;
+        type S = TGLWE<N, K>;
+
+        let mut rng = rand::thread_rng();
+        let msg_dist = Uniform::new(0_u64, T);
+
+        for _ in 0..200 {
+            let (sk, pk) = S::new_key(&mut rng)?;
+
+            let m = Rq::<T, N>::rand_u64(&mut rng, msg_dist)?;
+            let p: Tn<N> = S::encode::<T>(&m);
+
+            let c = S::encrypt(&mut rng, &pk, &p)?;
+            let p_recovered = c.decrypt(&sk);
+            let m_recovered = S::decode::<T>(&p_recovered);
+
+            assert_eq!(m, m_recovered);
+
+            // same but using encrypt_s (with sk instead of pk))
+            let c = S::encrypt_s(&mut rng, &sk, &p)?;
+            let p_recovered = c.decrypt(&sk);
+            let m_recovered = S::decode::<T>(&p_recovered);
+
+            assert_eq!(m, m_recovered);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_addition() -> Result<()> {
+        const T: u64 = 128;
+        const N: usize = 64;
+        const K: usize = 16;
+        type S = TGLWE<N, K>;
+
+        let mut rng = rand::thread_rng();
+        let msg_dist = Uniform::new(0_u64, T);
+
+        for _ in 0..200 {
+            let (sk, pk) = S::new_key(&mut rng)?;
+
+            let m1 = Rq::<T, N>::rand_u64(&mut rng, msg_dist)?;
+            let m2 = Rq::<T, N>::rand_u64(&mut rng, msg_dist)?;
+            let p1: Tn<N> = S::encode::<T>(&m1); // plaintext
+            let p2: Tn<N> = S::encode::<T>(&m2); // plaintext
+
+            let c1 = S::encrypt(&mut rng, &pk, &p1)?;
+            let c2 = S::encrypt(&mut rng, &pk, &p2)?;
+
+            let c3 = c1 + c2;
+
+            let p3_recovered = c3.decrypt(&sk);
+            let m3_recovered = S::decode::<T>(&p3_recovered);
+
+            assert_eq!((m1 + m2).remodule::<T>(), m3_recovered.remodule::<T>());
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_add_plaintext() -> Result<()> {
+        const T: u64 = 128;
+        const N: usize = 64;
+        const K: usize = 16;
+        type S = TGLWE<N, K>;
+
+        let mut rng = rand::thread_rng();
+        let msg_dist = Uniform::new(0_u64, T);
+
+        for _ in 0..200 {
+            let (sk, pk) = S::new_key(&mut rng)?;
+
+            let m1 = Rq::<T, N>::rand_u64(&mut rng, msg_dist)?;
+            let m2 = Rq::<T, N>::rand_u64(&mut rng, msg_dist)?;
+            let p1: Tn<N> = S::encode::<T>(&m1); // plaintext
+            let p2: Tn<N> = S::encode::<T>(&m2); // plaintext
+
+            let c1 = S::encrypt(&mut rng, &pk, &p1)?;
+
+            let c3 = c1 + p2;
+
+            let p3_recovered = c3.decrypt(&sk);
+            let m3_recovered = S::decode::<T>(&p3_recovered);
+
+            assert_eq!(m1 + m2, m3_recovered);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_mul_plaintext() -> Result<()> {
+        const T: u64 = 128;
+        const N: usize = 64;
+        const K: usize = 16;
+        type S = TGLWE<N, K>;
+
+        let mut rng = rand::thread_rng();
+        let msg_dist = Uniform::new(0_u64, T);
+
+        for _ in 0..200 {
+            let (sk, pk) = S::new_key(&mut rng)?;
+
+            let m1 = Rq::<T, N>::rand_u64(&mut rng, msg_dist)?;
+            let m2 = Rq::<T, N>::rand_u64(&mut rng, msg_dist)?;
+            let p1: Tn<N> = S::encode::<T>(&m1);
+            // don't scale up p2, set it directly from m2
+            let p2: Tn<N> = Tn(array::from_fn(|i| T64(m2.coeffs()[i].0)));
+
+            let c1 = S::encrypt(&mut rng, &pk, &p1)?;
+
+            let c3 = c1 * p2;
+
+            let p3_recovered: Tn<N> = c3.decrypt(&sk);
+            let m3_recovered = S::decode::<T>(&p3_recovered);
+            assert_eq!((m1.to_r() * m2.to_r()).to_rq::<T>(), m3_recovered);
+        }
+
+        Ok(())
+    }
+}