fix(shortint): add ciphertext_modulus_after_packing_ks to compression…

… parameters

tfhe/src/integer/gpu/client_key/radix.rs

@@ -43,7 +43,7 @@ impl RadixClientKey {
                 params.packing_ks_base_log,
                 params.packing_ks_level,
                 params.packing_ks_key_noise_distribution,
-                self.parameters().ciphertext_modulus(),
+                params.ciphertext_modulus_after_packing_ks,
                 &mut engine.encryption_generator,
             )
         });

tfhe/src/shortint/list_compression/compressed_server_keys.rs

@@ -103,7 +103,7 @@ impl ClientKey {
                 params.packing_ks_base_log,
                 params.packing_ks_level,
                 params.packing_ks_key_noise_distribution,
-                self.parameters.ciphertext_modulus(),
+                params.ciphertext_modulus_after_packing_ks,
                 &mut engine.seeder,
             )
         });

tfhe/src/shortint/list_compression/compression.rs

@@ -25,7 +25,9 @@ impl CompressionKey {
         let lwe_pksk = &self.packing_key_switching_key;
 
         let polynomial_size = lwe_pksk.output_polynomial_size();
-        let ciphertext_modulus = lwe_pksk.ciphertext_modulus();
+
+        let out_ciphertext_modulus = lwe_pksk.ciphertext_modulus();
+
         let glwe_size = lwe_pksk.output_glwe_size();
         let lwe_size = lwe_pksk.input_key_lwe_dimension().to_lwe_size();
 
@@ -43,6 +45,7 @@ impl CompressionKey {
         let message_modulus = first_ct.message_modulus;
         let carry_modulus = first_ct.carry_modulus;
         let pbs_order = first_ct.pbs_order;
+        let in_ciphertext_modulus = first_ct.ct.ciphertext_modulus();
 
         assert!(
             message_modulus.0 <= carry_modulus.0,
@@ -86,6 +89,12 @@ impl CompressionKey {
                         "All ciphertexts do not have the same pbs order"
                     );
 
+                    assert_eq!(
+                        in_ciphertext_modulus,
+                        ct.ct.ciphertext_modulus(),
+                        "All ciphertexts do not have the same ciphertext modulus"
+                    );
+
                     let mut ct = ct.clone();
                     let max_noise_level =
                         MaxNoiseLevel::new((ct.noise_level() * message_modulus.0).get());
@@ -94,12 +103,12 @@ impl CompressionKey {
                     list.extend(ct.ct.as_ref());
                 }
 
-                let list = LweCiphertextList::from_container(list, lwe_size, ciphertext_modulus);
+                let list = LweCiphertextList::from_container(list, lwe_size, in_ciphertext_modulus);
 
                 let bodies_count = LweCiphertextCount(ct_list.len());
 
                 let mut out =
-                    GlweCiphertext::new(0, glwe_size, polynomial_size, ciphertext_modulus);
+                    GlweCiphertext::new(0, glwe_size, polynomial_size, out_ciphertext_modulus);
 
                 par_keyswitch_lwe_ciphertext_list_and_pack_in_glwe_ciphertext(
                     lwe_pksk, &list, &mut out,
@@ -120,7 +129,7 @@ impl CompressionKey {
             pbs_order,
             lwe_per_glwe,
             count,
-            ciphertext_modulus,
+            ciphertext_modulus: out_ciphertext_modulus,
         }
     }
 }

tfhe/src/shortint/list_compression/server_keys.rs

@@ -65,7 +65,7 @@ impl ClientKey {
                 params.packing_ks_base_log,
                 params.packing_ks_level,
                 params.packing_ks_key_noise_distribution,
-                self.parameters.ciphertext_modulus(),
+                params.ciphertext_modulus_after_packing_ks,
                 &mut engine.encryption_generator,
             )
         });
@@ -116,6 +116,7 @@ pub struct CompressionConformanceParameters {
     pub packing_ks_base_log: DecompositionBaseLog,
     pub packing_ks_polynomial_size: PolynomialSize,
     pub packing_ks_glwe_dimension: GlweDimension,
+    pub ciphertext_modulus_after_packing_ks: CiphertextModulus<u64>,
     pub lwe_per_glwe: LweCiphertextCount,
     pub storage_log_modulus: CiphertextModulusLog,
     pub uncompressed_polynomial_size: PolynomialSize,
@@ -132,6 +133,8 @@ impl From<(PBSParameters, CompressionParameters)> for CompressionConformancePara
             packing_ks_base_log: compression_params.packing_ks_base_log,
             packing_ks_polynomial_size: compression_params.packing_ks_polynomial_size,
             packing_ks_glwe_dimension: compression_params.packing_ks_glwe_dimension,
+            ciphertext_modulus_after_packing_ks: compression_params
+                .ciphertext_modulus_after_packing_ks,
             lwe_per_glwe: compression_params.lwe_per_glwe,
             storage_log_modulus: compression_params.storage_log_modulus,
             uncompressed_polynomial_size: pbs_params.polynomial_size(),
@@ -159,7 +162,7 @@ impl ParameterSetConformant for CompressionKey {
                 .to_equivalent_lwe_dimension(parameter_set.uncompressed_polynomial_size),
             output_glwe_size: parameter_set.packing_ks_glwe_dimension.to_glwe_size(),
             output_polynomial_size: parameter_set.packing_ks_polynomial_size,
-            ciphertext_modulus: parameter_set.cipherext_modulus,
+            ciphertext_modulus: parameter_set.ciphertext_modulus_after_packing_ks,
         };
 
         packing_key_switching_key.is_conformant(&params)

tfhe/src/shortint/parameters/list_compression.rs

@@ -1,5 +1,6 @@
 use tfhe_versionable::Versionize;
 
+use super::CiphertextModulus;
 use crate::core_crypto::prelude::{CiphertextModulusLog, LweCiphertextCount};
 use crate::shortint::backward_compatibility::parameters::list_compression::CompressionParametersVersions;
 use crate::shortint::parameters::{
@@ -20,6 +21,7 @@ pub struct CompressionParameters {
     pub lwe_per_glwe: LweCiphertextCount,
     pub storage_log_modulus: CiphertextModulusLog,
     pub packing_ks_key_noise_distribution: DynamicDistribution<u64>,
+    pub ciphertext_modulus_after_packing_ks: CiphertextModulus,
 }
 
 pub const COMP_PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64: CompressionParameters =
@@ -33,4 +35,5 @@ pub const COMP_PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64: CompressionParamete
         lwe_per_glwe: LweCiphertextCount(256),
         storage_log_modulus: CiphertextModulusLog(12),
         packing_ks_key_noise_distribution: DynamicDistribution::new_t_uniform(42),
+        ciphertext_modulus_after_packing_ks: CiphertextModulus::new_native(),
     };