arnaucube
arnaucube/poulpyPublic Self-hosted repository
Added noise equation for keyswitch over GGSW & updated associated test
Jean-Philippe Bossuat jeanphilippe.bossuat@gmail.com
Tue, 20 May 2025 14:36:26 +0200
commit

a803127424bdb81c0317b25ebe3053594a8822d1

parent

7d84477e6411390bc312306a5ea66f4de4e930d2

5 files changed, 107 insertions(+), 29 deletions(-)

jump to
M core/src/test_fft64/automorphism_key.rs → core/src/test_fft64/automorphism_key.rs 
@@ -7,7 +7,7 @@ elem::{GetRow, Infos},
     glwe_ciphertext_fourier::GLWECiphertextFourier,
     glwe_plaintext::GLWEPlaintext,
     keys::{SecretKey, SecretKeyFourier},
-    test_fft64::gglwe::noise_gglwe_product,
+    test_fft64::gglwe::log2_std_noise_gglwe_product,
 };
 
 #[test]

@@ -101,7 +101,7 @@ ct_glwe_dft.decrypt(&module, &mut pt, &sk_auto_dft, scratch.borrow());
             module.vec_znx_sub_scalar_inplace(&mut pt, 0, row_i, &sk, col_i);
 
             let noise_have: f64 = pt.data.std(0, basek).log2();
-            let noise_want: f64 = noise_gglwe_product(
+            let noise_want: f64 = log2_std_noise_gglwe_product(
                 module.n() as f64,
                 basek,
                 0.5,

@@ -192,7 +192,7 @@ ct_glwe_dft.decrypt(&module, &mut pt, &sk_auto_dft, scratch.borrow());
             module.vec_znx_sub_scalar_inplace(&mut pt, 0, row_i, &sk, col_i);
 
             let noise_have: f64 = pt.data.std(0, basek).log2();
-            let noise_want: f64 = noise_gglwe_product(
+            let noise_want: f64 = log2_std_noise_gglwe_product(
                 module.n() as f64,
                 basek,
                 0.5,
M core/src/test_fft64/gglwe.rs → core/src/test_fft64/gglwe.rs 
@@ -212,7 +212,7 @@ ct_glwe_dft.decrypt(&module, &mut pt, &sk2_dft, scratch.borrow());
             module.vec_znx_sub_scalar_inplace(&mut pt, 0, row_i, &sk0, col_i);
 
             let noise_have: f64 = pt.data.std(0, basek).log2();
-            let noise_want: f64 = noise_gglwe_product(
+            let noise_want: f64 = log2_std_noise_gglwe_product(
                 module.n() as f64,
                 basek,
                 0.5,

@@ -314,7 +314,7 @@ ct_glwe_dft.decrypt(&module, &mut pt, &sk2_dft, scratch.borrow());
             module.vec_znx_sub_scalar_inplace(&mut pt, 0, row_i, &sk0, col_i);
 
             let noise_have: f64 = pt.data.std(0, basek).log2();
-            let noise_want: f64 = noise_gglwe_product(
+            let noise_want: f64 = log2_std_noise_gglwe_product(
                 module.n() as f64,
                 basek,
                 0.5,

@@ -571,7 +571,7 @@ });
     });
 }
 
-pub(crate) fn noise_gglwe_product(
+pub(crate) fn var_noise_gglwe_product(
     n: f64,
     basek: usize,
     var_xs: f64,

@@ -597,7 +597,34 @@ // rhs = a_cols * n * var_base * var_gct_err_rhs * var_xs
     let mut noise: f64 = (a_cols as f64) * n * var_base * (var_gct_err_lhs + var_xs * var_gct_err_rhs);
     noise += var_msg * var_a_err * a_scale * a_scale * n;
     noise *= rank_in;
+    noise /= b_scale * b_scale;
+    noise
+}
+
+pub(crate) fn log2_std_noise_gglwe_product(
+    n: f64,
+    basek: usize,
+    var_xs: f64,
+    var_msg: f64,
+    var_a_err: f64,
+    var_gct_err_lhs: f64,
+    var_gct_err_rhs: f64,
+    rank_in: f64,
+    a_logq: usize,
+    b_logq: usize,
+) -> f64 {
+    let mut noise: f64 = var_noise_gglwe_product(
+        n,
+        basek,
+        var_xs,
+        var_msg,
+        var_a_err,
+        var_gct_err_lhs,
+        var_gct_err_rhs,
+        rank_in,
+        a_logq,
+        b_logq,
+    );
     noise = noise.sqrt();
-    noise /= b_scale;
     noise.log2().min(-1.0) // max noise is [-2^{-1}, 2^{-1}]
 }
M core/src/test_fft64/ggsw.rs → core/src/test_fft64/ggsw.rs 
@@ -13,8 +13,10 @@ glwe_plaintext::GLWEPlaintext,
     keys::{SecretKey, SecretKeyFourier},
     keyswitch_key::GLWESwitchingKey,
     tensor_key::TensorKey,
-    test_fft64::gglwe::noise_gglwe_product,
+    test_fft64::gglwe::log2_std_noise_gglwe_product,
 };
+
+use super::gglwe::var_noise_gglwe_product;
 
 #[test]
 fn encrypt_sk() {

@@ -146,14 +148,16 @@ rank,
             ),
     );
 
+    let var_xs: f64 = 0.5;
+
     let mut sk_in: SecretKey<Vec<u8>> = SecretKey::new(&module, rank);
-    sk_in.fill_ternary_prob(0.5, &mut source_xs);
+    sk_in.fill_ternary_prob(var_xs, &mut source_xs);
 
     let mut sk_in_dft: SecretKeyFourier<Vec<u8>, FFT64> = SecretKeyFourier::new(&module, rank);
     sk_in_dft.dft(&module, &sk_in);
 
     let mut sk_out: SecretKey<Vec<u8>> = SecretKey::new(&module, rank);
-    sk_out.fill_ternary_prob(0.5, &mut source_xs);
+    sk_out.fill_ternary_prob(var_xs, &mut source_xs);
 
     let mut sk_out_dft: SecretKeyFourier<Vec<u8>, FFT64> = SecretKeyFourier::new(&module, rank);
     sk_out_dft.dft(&module, &sk_out);

@@ -213,11 +217,11 @@
             module.vec_znx_sub_ab_inplace(&mut pt_have, 0, &pt_want, 0);
 
             let noise_have: f64 = pt_have.data.std(0, basek).log2();
-            let noise_want: f64 = noise_gglwe_product(
+            let noise_want: f64 = noise_ggsw_keyswitch(
                 module.n() as f64,
                 basek,
-                0.5,
-                0.5,
+                col_j,
+                var_xs,
                 0f64,
                 sigma * sigma,
                 0f64,

@@ -226,18 +230,65 @@ k,
                 k,
             );
 
-            println!("{} {}", noise_have, noise_want);
-
-            // assert!(
-            // (noise_have - noise_want).abs() <= 0.1,
-            // "{} {}",
-            // noise_have,
-            // noise_want
-            // );
+            assert!(
+                (noise_have - noise_want).abs() <= 0.1,
+                "{} {}",
+                noise_have,
+                noise_want
+            );
 
             pt_want.data.zero();
         });
     });
+}
+
+pub(crate) fn noise_ggsw_keyswitch(
+    n: f64,
+    basek: usize,
+    col: usize,
+    var_xs: f64,
+    var_a_err: f64,
+    var_gct_err_lhs: f64,
+    var_gct_err_rhs: f64,
+    rank: f64,
+    a_logq: usize,
+    b_logq: usize,
+) -> f64 {
+    let var_si_x_sj: f64 = n * var_xs * var_xs;
+
+    // Initial KS for col = 0
+    let mut noise: f64 = var_noise_gglwe_product(
+        n,
+        basek,
+        var_xs,
+        var_xs,
+        var_a_err,
+        var_gct_err_lhs,
+        var_gct_err_rhs,
+        rank,
+        a_logq,
+        b_logq,
+    );
+
+    // Other GGSW reconstruction for col > 0
+    if col > 0 {
+        noise += var_noise_gglwe_product(
+            n,
+            basek,
+            var_xs,
+            var_si_x_sj,
+            var_a_err + 1f64 / 12.0,
+            var_gct_err_lhs,
+            var_gct_err_rhs,
+            rank,
+            a_logq,
+            b_logq,
+        );
+        noise += n * noise * var_xs * 0.5;
+    }
+
+    noise = noise.sqrt();
+    noise.log2().min(-1.0) // max noise is [-2^{-1}, 2^{-1}]
 }
 
 // fn test_automorphism(p: i64, log_n: usize, basek: usize, k: usize, rank: usize, sigma: f64) {
M core/src/test_fft64/glwe.rs → core/src/test_fft64/glwe.rs 
@@ -14,7 +14,7 @@ glwe_ciphertext_fourier::GLWECiphertextFourier,
     glwe_plaintext::GLWEPlaintext,
     keys::{GLWEPublicKey, SecretKey, SecretKeyFourier},
     keyswitch_key::GLWESwitchingKey,
-    test_fft64::{gglwe::noise_gglwe_product, ggsw::noise_ggsw_product},
+    test_fft64::{gglwe::log2_std_noise_gglwe_product, ggsw::noise_ggsw_product},
 };
 
 #[test]

@@ -326,7 +326,7 @@
     module.vec_znx_sub_ab_inplace(&mut pt_have, 0, &pt_want, 0);
 
     let noise_have: f64 = pt_have.data.std(0, basek).log2();
-    let noise_want: f64 = noise_gglwe_product(
+    let noise_want: f64 = log2_std_noise_gglwe_product(
         module.n() as f64,
         basek,
         0.5,

@@ -411,7 +411,7 @@
     module.vec_znx_sub_ab_inplace(&mut pt_have, 0, &pt_want, 0);
 
     let noise_have: f64 = pt_have.data.std(0, basek).log2();
-    let noise_want: f64 = noise_gglwe_product(
+    let noise_want: f64 = log2_std_noise_gglwe_product(
         module.n() as f64,
         basek,
         0.5,

@@ -502,7 +502,7 @@ let noise_have: f64 = pt_have.data.std(0, basek).log2();
 
     println!("{}", noise_have);
 
-    let noise_want: f64 = noise_gglwe_product(
+    let noise_want: f64 = log2_std_noise_gglwe_product(
         module.n() as f64,
         basek,
         0.5,

@@ -581,7 +581,7 @@ module.vec_znx_sub_ab_inplace(&mut pt_have, 0, &pt_want, 0);
     module.vec_znx_normalize_inplace(basek, &mut pt_have, 0, scratch.borrow());
 
     let noise_have: f64 = pt_have.data.std(0, basek).log2();
-    let noise_want: f64 = noise_gglwe_product(
+    let noise_want: f64 = log2_std_noise_gglwe_product(
         module.n() as f64,
         basek,
         0.5,
M core/src/test_fft64/glwe_fourier.rs → core/src/test_fft64/glwe_fourier.rs 
@@ -6,7 +6,7 @@ glwe_ciphertext_fourier::GLWECiphertextFourier,
     glwe_plaintext::GLWEPlaintext,
     keys::{SecretKey, SecretKeyFourier},
     keyswitch_key::GLWESwitchingKey,
-    test_fft64::{gglwe::noise_gglwe_product, ggsw::noise_ggsw_product},
+    test_fft64::{gglwe::log2_std_noise_gglwe_product, ggsw::noise_ggsw_product},
 };
 use base2k::{FFT64, FillUniform, Module, ScalarZnx, ScalarZnxAlloc, ScratchOwned, Stats, VecZnxOps, VecZnxToMut, ZnxViewMut};
 use sampling::source::Source;

@@ -132,7 +132,7 @@
     module.vec_znx_sub_ab_inplace(&mut pt_have, 0, &pt_want, 0);
 
     let noise_have: f64 = pt_have.data.std(0, basek).log2();
-    let noise_want: f64 = noise_gglwe_product(
+    let noise_want: f64 = log2_std_noise_gglwe_product(
         module.n() as f64,
         basek,
         0.5,

@@ -220,7 +220,7 @@
     module.vec_znx_sub_ab_inplace(&mut pt_have, 0, &pt_want, 0);
 
     let noise_have: f64 = pt_have.data.std(0, basek).log2();
-    let noise_want: f64 = noise_gglwe_product(
+    let noise_want: f64 = log2_std_noise_gglwe_product(
         module.n() as f64,
         basek,
         0.5,