test(core): use 5 bits parameters tweaked to 4 bits to avoid high pfail

zama-ai · Jan 17, 2025 · aa5b431 · aa5b431
1 parent 2b914ae
commit aa5b431
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Showing 2 changed files with 31 additions and 28 deletions.
diff --git a/tfhe/src/core_crypto/experimental/algorithms/test/lwe_fast_keyswitch.rs b/tfhe/src/core_crypto/experimental/algorithms/test/lwe_fast_keyswitch.rs
@@ -13,7 +13,7 @@ pub struct FastKSParam<Scalar: UnsignedInteger> {
     pub bsk_partial_glwe_secret_key_fill: PartialGlweSecretKeyRandomCoefCount,
     pub bsk_glwe_noise_distribution: DynamicDistribution<Scalar>,
     pub lwe_dimension: LweDimension,
-    pub ks1_lwe_modular_std_dev: DynamicDistribution<Scalar>,
+    pub ks1_lwe_modular_noise_distribution: DynamicDistribution<Scalar>,
     pub pbs_level: DecompositionLevelCount,
     pub pbs_base_log: DecompositionBaseLog,
     pub ks1_level: DecompositionLevelCount,
@@ -25,27 +25,28 @@ pub struct FastKSParam<Scalar: UnsignedInteger> {
     pub ciphertext_modulus: CiphertextModulus<Scalar>,
 }
 
+/// This is the original precision 5 parameters tweaked to use for 4 bits, such that the pfail is
+/// much lower than 2^-14, it should be approximately ~2^-49
 pub const PRECISION_4_FAST_KS: FastKSParam<u64> = FastKSParam {
-    log_precision: MessageModulusLog(4),
-    _log_mu: 4,
-    glwe_dimension: GlweDimension(2),
-    polynomial_size: PolynomialSize(1024),
+    log_precision: MessageModulusLog(4), // original: log_precision: 5,
+    _log_mu: 5,
+    glwe_dimension: GlweDimension(1),
+    polynomial_size: PolynomialSize(2048),
     bsk_partial_glwe_secret_key_fill: PartialGlweSecretKeyRandomCoefCount(2048),
     bsk_glwe_noise_distribution: DynamicDistribution::new_gaussian_from_std_dev(StandardDev(
         3.162026630747649e-16,
     )),
-    lwe_dimension: LweDimension(682),
-    ks1_lwe_modular_std_dev: DynamicDistribution::new_gaussian_from_std_dev(StandardDev(
-        2.7313997525878062e-5,
-    )),
+    lwe_dimension: LweDimension(766),
+    ks1_lwe_modular_noise_distribution: DynamicDistribution::new_gaussian_from_std_dev(
+        StandardDev(5.822_216_831_056_818e-6),
+    ),
     pbs_level: DecompositionLevelCount(1),
     pbs_base_log: DecompositionBaseLog(23),
-    ks1_level: DecompositionLevelCount(14),
+    ks1_level: DecompositionLevelCount(15),
     ks1_base_log: DecompositionBaseLog(1),
     ks1_polynomial_size: PolynomialSize(512),
-    ks_in_glwe_dimension: GlweDimension(3), // Original value
-    // ks_in_glwe_dimension: GlweDimension(4), // Test non square pseudo GGSWs
-    phi_in: 1366,
+    ks_in_glwe_dimension: GlweDimension(3),
+    phi_in: 1282,
     ks_out_glwe_dimension: GlweDimension(3),
     ciphertext_modulus: CiphertextModulus::new_native(),
 };
@@ -71,7 +72,7 @@ fn lwe_encrypt_fast_ks_decrypt_custom_mod<
         bsk_partial_glwe_secret_key_fill,
         bsk_glwe_noise_distribution,
         lwe_dimension,
-        ks1_lwe_modular_std_dev,
+        ks1_lwe_modular_noise_distribution,
         pbs_level,
         pbs_base_log,
         ks1_level,
@@ -222,7 +223,7 @@ fn lwe_encrypt_fast_ks_decrypt_custom_mod<
         &small_glwe_secret_key,
         &large_glwe_secret_key_unshared,
         &mut ggsw,
-        ks1_lwe_modular_std_dev,
+        ks1_lwe_modular_noise_distribution,
         &mut rsc.encryption_random_generator,
     );
 

diff --git a/tfhe/src/core_crypto/experimental/algorithms/test/lwe_stair_keyswitch.rs b/tfhe/src/core_crypto/experimental/algorithms/test/lwe_stair_keyswitch.rs
@@ -29,30 +29,32 @@ pub struct StairKSParam<Scalar: UnsignedInteger> {
     pub ciphertext_modulus: CiphertextModulus<Scalar>,
 }
 
+/// This is the original precision 5 parameters tweaked to use for 4 bits, such that the pfail is
+/// much lower than 2^-14, it should be approximately ~2^-49
 pub const PRECISION_4_STAIR: StairKSParam<u64> = StairKSParam {
-    log_precision: MessageModulusLog(4),
-    _log_mu: 4,
-    glwe_dimension: GlweDimension(2),
-    polynomial_size: PolynomialSize(1024),
+    log_precision: MessageModulusLog(4), //original: log_precision: 5,
+    _log_mu: 5,
+    glwe_dimension: GlweDimension(1),
+    polynomial_size: PolynomialSize(2048),
     partial_glwe_secret_key_fill: PartialGlweSecretKeyRandomCoefCount(2048),
     bsk_glwe_noise_distribution: DynamicDistribution::new_gaussian_from_std_dev(StandardDev(
         3.16202663074765e-16,
     )),
-    lwe_dimension: LweDimension(664),
+    lwe_dimension: LweDimension(732),
     ks1_lwe_noise_distribution: DynamicDistribution::new_gaussian_from_std_dev(StandardDev(
-        7.60713313301797e-9,
+        3.31119701700870e-9,
     )),
     ks2_lwe_noise_distribution: DynamicDistribution::new_gaussian_from_std_dev(StandardDev(
-        0.0000380960250519291,
+        0.0000108646407745138,
     )),
     pbs_level: DecompositionLevelCount(1),
-    pbs_base_log: DecompositionBaseLog(22),
-    ks1_level: DecompositionLevelCount(1),
-    ks1_base_log: DecompositionBaseLog(13),
-    ks2_level: DecompositionLevelCount(6),
+    pbs_base_log: DecompositionBaseLog(23),
+    ks1_level: DecompositionLevelCount(2),
+    ks1_base_log: DecompositionBaseLog(9),
+    ks2_level: DecompositionLevelCount(7),
     ks2_base_log: DecompositionBaseLog(2),
-    ks1_unshared_coeff_count: LweSecretKeyUnsharedCoefCount(922),
-    ks2_unshared_coeff_count: LweSecretKeyUnsharedCoefCount(462),
+    ks1_unshared_coeff_count: LweSecretKeyUnsharedCoefCount(877),
+    ks2_unshared_coeff_count: LweSecretKeyUnsharedCoefCount(439),
     ciphertext_modulus: CiphertextModulus::new_native(),
 };