fix(shortint): add ciphertext_modulus_after_packing_ks to compression parameters

tfhe/src/core_crypto/algorithms/lwe_packing_keyswitch.rs

@@ -135,12 +135,11 @@ pub fn keyswitch_lwe_ciphertext_into_glwe_ciphertext<Scalar, KeyCont, InputCont,
     );
 
     assert!(
-        lwe_pksk.ciphertext_modulus() == input_lwe_ciphertext.ciphertext_modulus(),
-        "Mismatched CiphertextModulus. \
-        LwePackingKeyswitchKey CiphertextModulus: {:?}, input LweCiphertext CiphertextModulus {:?}.",
-        lwe_pksk.ciphertext_modulus(),
+         input_lwe_ciphertext.ciphertext_modulus().is_compatible_with_native_modulus(),
+        "input LweCiphertext CiphertextModulus {:?} must be is compatible with native modulus for decomposition",
         input_lwe_ciphertext.ciphertext_modulus()
     );
+
     assert!(
         lwe_pksk.ciphertext_modulus() == output_glwe_ciphertext.ciphertext_modulus(),
         "Mismatched CiphertextModulus. \
@@ -334,12 +333,11 @@ pub fn keyswitch_lwe_ciphertext_list_and_pack_in_glwe_ciphertext<
     );
 
     assert!(
-        lwe_pksk.ciphertext_modulus() == input_lwe_ciphertext.ciphertext_modulus(),
-        "Mismatched CiphertextModulus. \
-        LwePackingKeyswitchKey CiphertextModulus: {:?}, input LweCiphertext CiphertextModulus {:?}.",
-        lwe_pksk.ciphertext_modulus(),
-        input_lwe_ciphertext.ciphertext_modulus()
-    );
+        input_lwe_ciphertext.ciphertext_modulus().is_compatible_with_native_modulus(),
+       "input LweCiphertext CiphertextModulus {:?} must be is compatible with native modulus for decomposition",
+       input_lwe_ciphertext.ciphertext_modulus()
+   );
+
     assert!(
         lwe_pksk.ciphertext_modulus() == output_glwe_ciphertext.ciphertext_modulus(),
         "Mismatched CiphertextModulus. \
@@ -665,12 +663,11 @@ pub fn par_keyswitch_lwe_ciphertext_list_and_pack_in_glwe_ciphertext_with_thread
     );
 
     assert!(
-        lwe_pksk.ciphertext_modulus() == input_lwe_ciphertext_list.ciphertext_modulus(),
-        "Mismatched CiphertextModulus. \
-        LwePackingKeyswitchKey CiphertextModulus: {:?}, input LweCiphertext CiphertextModulus {:?}.",
-        lwe_pksk.ciphertext_modulus(),
-        input_lwe_ciphertext_list.ciphertext_modulus()
-    );
+        input_lwe_ciphertext_list.ciphertext_modulus().is_compatible_with_native_modulus(),
+       "input LweCiphertext CiphertextModulus {:?} must be is compatible with native modulus for decomposition",
+       input_lwe_ciphertext_list.ciphertext_modulus()
+   );
+
     assert!(
         lwe_pksk.ciphertext_modulus() == output_glwe_ciphertext.ciphertext_modulus(),
         "Mismatched CiphertextModulus. \

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/backward_compatibility/parameters/list_compression.rs

@@ -1,8 +1,59 @@
-use tfhe_versionable::VersionsDispatch;
-
 use super::parameters::list_compression::CompressionParameters;
+use super::CiphertextModulus;
+use crate::core_crypto::prelude::{CiphertextModulusLog, LweCiphertextCount};
+use crate::shortint::parameters::{
+    DecompositionBaseLog, DecompositionLevelCount, DynamicDistribution, GlweDimension,
+    PolynomialSize,
+};
+use std::convert::Infallible;
+use tfhe_versionable::{Upgrade, Version, VersionsDispatch};
+
+#[derive(Version)]
+pub struct CompressionParametersV0 {
+    pub br_level: DecompositionLevelCount,
+    pub br_base_log: DecompositionBaseLog,
+    pub packing_ks_level: DecompositionLevelCount,
+    pub packing_ks_base_log: DecompositionBaseLog,
+    pub packing_ks_polynomial_size: PolynomialSize,
+    pub packing_ks_glwe_dimension: GlweDimension,
+    pub lwe_per_glwe: LweCiphertextCount,
+    pub storage_log_modulus: CiphertextModulusLog,
+    pub packing_ks_key_noise_distribution: DynamicDistribution<u64>,
+}
+
+impl Upgrade<CompressionParameters> for CompressionParametersV0 {
+    type Error = Infallible;
+
+    fn upgrade(self) -> Result<CompressionParameters, Self::Error> {
+        let Self {
+            br_level,
+            br_base_log,
+            packing_ks_level,
+            packing_ks_base_log,
+            packing_ks_polynomial_size,
+            packing_ks_glwe_dimension,
+            lwe_per_glwe,
+            storage_log_modulus,
+            packing_ks_key_noise_distribution,
+        } = self;
+
+        Ok(CompressionParameters {
+            br_level,
+            br_base_log,
+            packing_ks_level,
+            packing_ks_base_log,
+            packing_ks_polynomial_size,
+            packing_ks_glwe_dimension,
+            lwe_per_glwe,
+            storage_log_modulus,
+            packing_ks_key_noise_distribution,
+            ciphertext_modulus_after_packing_ks: CiphertextModulus::new_native(),
+        })
+    }
+}
 
 #[derive(VersionsDispatch)]
 pub enum CompressionParametersVersions {
-    V0(CompressionParameters),
+    V0(CompressionParametersV0),
+    V1(CompressionParameters),
 }

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

@@ -2,8 +2,9 @@ use super::{CompressionKey, DecompressionKey};
 use crate::core_crypto::prelude::compressed_modulus_switched_glwe_ciphertext::CompressedModulusSwitchedGlweCiphertext;
 use crate::core_crypto::prelude::{
     extract_lwe_sample_from_glwe_ciphertext,
-    par_keyswitch_lwe_ciphertext_list_and_pack_in_glwe_ciphertext, CiphertextCount, GlweCiphertext,
-    LweCiphertext, LweCiphertextCount, LweCiphertextList, MonomialDegree,
+    par_keyswitch_lwe_ciphertext_list_and_pack_in_glwe_ciphertext, CiphertextCount,
+    CiphertextModulus, GlweCiphertext, LweCiphertext, LweCiphertextCount, LweCiphertextList,
+    MonomialDegree,
 };
 use crate::shortint::ciphertext::CompressedCiphertextList;
 use crate::shortint::engine::ShortintEngine;
@@ -11,7 +12,7 @@ use crate::shortint::parameters::{CarryModulus, MessageModulus, NoiseLevel};
 use crate::shortint::server_key::{
     apply_programmable_bootstrap, generate_lookup_table_with_encoding, unchecked_scalar_mul_assign,
 };
-use crate::shortint::{Ciphertext, CiphertextModulus, MaxNoiseLevel};
+use crate::shortint::{Ciphertext, MaxNoiseLevel};
 use rayon::iter::ParallelIterator;
 use rayon::slice::ParallelSlice;
 
@@ -25,7 +26,9 @@ 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 +46,7 @@ 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 +90,12 @@ 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 +104,12 @@ 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 +130,7 @@ impl CompressionKey {
             pbs_order,
             lwe_per_glwe,
             count,
-            ciphertext_modulus,
+            ciphertext_modulus: out_ciphertext_modulus,
         }
     }
 }
@@ -147,6 +157,9 @@ impl DecompressionKey {
             )));
         }
 
+        let in_ciphertext_modulus = packed.ciphertext_modulus;
+        let out_ciphertext_modulus = CiphertextModulus::new_native();
+
         let encryption_cleartext_modulus = packed.message_modulus.0 * packed.carry_modulus.0;
         // We multiply by message_modulus during compression so the actual modulus for the
         // compression is smaller
@@ -157,7 +170,7 @@ impl DecompressionKey {
         let decompression_rescale = generate_lookup_table_with_encoding(
             self.out_glwe_size(),
             self.out_polynomial_size(),
-            packed.ciphertext_modulus,
+            out_ciphertext_modulus,
             // Input moduli are the effective compression ones
             effective_compression_message_modulus,
             effective_compression_carry_modulus,
@@ -172,7 +185,6 @@ impl DecompressionKey {
         );
 
         let polynomial_size = packed.modulus_switched_glwe_ciphertext_list[0].polynomial_size();
-        let ciphertext_modulus = packed.ciphertext_modulus;
         let glwe_dimension = packed.modulus_switched_glwe_ciphertext_list[0].glwe_dimension();
 
         let lwe_per_glwe = packed.lwe_per_glwe.0;
@@ -187,7 +199,7 @@ impl DecompressionKey {
 
         let monomial_degree = MonomialDegree(index % lwe_per_glwe);
 
-        let mut intermediate_lwe = LweCiphertext::new(0, lwe_size, ciphertext_modulus);
+        let mut intermediate_lwe = LweCiphertext::new(0, lwe_size, in_ciphertext_modulus);
 
         extract_lwe_sample_from_glwe_ciphertext(
             &packed_glwe,
@@ -198,7 +210,7 @@ impl DecompressionKey {
         let mut output_br = LweCiphertext::new(
             0,
             self.blind_rotate_key.output_lwe_dimension().to_lwe_size(),
-            ciphertext_modulus,
+            out_ciphertext_modulus,
         );
 
         ShortintEngine::with_thread_local_mut(|engine| {
@@ -231,6 +243,7 @@ impl DecompressionKey {
 #[cfg(test)]
 mod test {
     use super::*;
+    use crate::shortint::list_compression::CompressionPrivateKeys;
     use crate::shortint::parameters::list_compression::COMP_PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64;
     use crate::shortint::parameters::PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64;
     use crate::shortint::{gen_keys, ClientKey};
@@ -241,7 +254,7 @@ mod test {
         // Generate the client key and the server key:
         let (cks, _sks) = gen_keys(PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64);
 
-        let private_compression_key: crate::shortint::list_compression::CompressionPrivateKeys =
+        let private_compression_key: CompressionPrivateKeys =
             cks.new_compression_private_key(COMP_PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64);
 
         let (compression_key, decompression_key) =

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 =
@@ -36,4 +38,5 @@ pub const V0_11_COMP_PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64: CompressionPa
         lwe_per_glwe: LweCiphertextCount(256),
         storage_log_modulus: CiphertextModulusLog(12),
         packing_ks_key_noise_distribution: DynamicDistribution::new_t_uniform(43),
+        ciphertext_modulus_after_packing_ks: CiphertextModulus::new_native(),
     };

tfhe/src/shortint/parameters/v0_10/list_compression.rs

@@ -1,4 +1,4 @@
-use crate::core_crypto::prelude::{CiphertextModulusLog, LweCiphertextCount};
+use crate::core_crypto::prelude::{CiphertextModulus, CiphertextModulusLog, LweCiphertextCount};
 use crate::shortint::parameters::{
     CompressionParameters, DecompositionBaseLog, DecompositionLevelCount, DynamicDistribution,
     GlweDimension, PolynomialSize,
@@ -15,4 +15,5 @@ pub const V0_10_COMP_PARAM_MESSAGE_2_CARRY_2_KS_PBS_TUNIFORM_2M64: CompressionPa
         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(),
     };