add zero_byte for fhe_uint & fix test for glwe blind selection

poulpy-schemes/src/tfhe/bdd_arithmetic/ciphertexts/fhe_uint.rs

@@ -234,20 +234,14 @@ impl<D: DataMut, T: UnsignedInteger> FheUint<D, T> {
         let trace_start = (T::LOG_BITS - T::LOG_BYTES) as usize;
         let rot: i64 = (T::bit_index(dst << 3) << log_gap) as i64;
 
-        // Move a to self and align byte
+        module.glwe_copy(self, a);
-        module.glwe_rotate(-rot, &mut self.bits, a);
 
-        // Stores this byte (everything else zeroed) into tmp_trace
+        self.zero_byte(module, dst, keys, scratch);
-        let (mut tmp_trace, scratch_1) = scratch.take_glwe(a);
-        module.glwe_trace(&mut tmp_trace, trace_start, self, keys, scratch_1);
-
-        // Subtracts to self to zero it
-        module.glwe_sub_inplace(&mut self.bits, &tmp_trace);
 
         // Isolate the byte to transfer from a
         let (mut tmp_fhe_uint_byte, scratch_1) = scratch.take_fhe_uint(b);
 
-        // Move a[byte_a] into a[0]
+        // Move a[byte_a] into a[dst]
         module.glwe_rotate(
             -((T::bit_index(src << 3) << log_gap) as i64),
             &mut tmp_fhe_uint_byte,
@@ -257,11 +251,11 @@ impl<D: DataMut, T: UnsignedInteger> FheUint<D, T> {
         // Zeroes all other bytes
         module.glwe_trace_inplace(&mut tmp_fhe_uint_byte, trace_start, keys, scratch_1);
 
+        // Moves back self[0] to self[byte_tg]
+        module.glwe_rotate_inplace(rot, &mut tmp_fhe_uint_byte, scratch_1);
+
         // Add self[0] += a[0]
         module.glwe_add_inplace(&mut self.bits, &tmp_fhe_uint_byte);
-
-        // Moves back self[0] to self[byte_tg]
-        module.glwe_rotate_inplace(rot, &mut self.bits, scratch);
     }
 }
 
@@ -313,6 +307,31 @@ impl<D: DataRef, T: UnsignedInteger> GLWEToRef for FheUint<D, T> {
 }
 
 impl<D: DataMut, T: UnsignedInteger> FheUint<D, T> {
+    pub fn zero_byte<M, K, H, BE: Backend>(&mut self, module: &M, byte: usize, keys: &H, scratch: &mut Scratch<BE>)
+    where
+        H: GLWEAutomorphismKeyHelper<K, BE>,
+        K: GGLWEPreparedToRef<BE> + GGLWEInfos + GetGaloisElement,
+        M: ModuleLogN + GLWERotate<BE> + GLWETrace<BE> + GLWESub + GLWEAdd + GLWECopy,
+        Scratch<BE>: ScratchTakeBDD<T, BE>,
+    {
+        let log_gap: usize = module.log_n() - T::LOG_BITS as usize;
+        let trace_start = (T::LOG_BITS - T::LOG_BYTES) as usize;
+        let rot: i64 = (T::bit_index(byte << 3) << log_gap) as i64;
+
+        // Move a to self and align byte
+        module.glwe_rotate_inplace(-rot, &mut self.bits, scratch);
+
+        // Stores this byte (everything else zeroed) into tmp_trace
+        let (mut tmp_trace, scratch_1) = scratch.take_glwe(self);
+        module.glwe_trace(&mut tmp_trace, trace_start, self, keys, scratch_1);
+
+        // Subtracts to self to zero it
+        module.glwe_sub_inplace(&mut self.bits, &tmp_trace);
+
+        // Move a to self and align byte
+        module.glwe_rotate_inplace(rot, &mut self.bits, scratch);
+    }
+
     pub fn sext<M, H, K, BE>(&mut self, module: &M, byte: usize, keys: &H, scratch: &mut Scratch<BE>)
     where
         M:,

poulpy-schemes/src/tfhe/bdd_arithmetic/tests/test_suite/fheuint.rs

@@ -58,7 +58,7 @@ where
 }
 
 pub fn sext(x: u32, byte: usize) -> u32 {
-    x | ((x >> (byte << 3)) & 1) * (0xFFFF_FFFF & (0xFFFF_FFFF << (byte << 3)))
+    x | (((x >> (byte << 3)) & 1) * (0xFFFF_FFFF << (byte << 3)))
 }
 
 pub fn test_fhe_uint_splice_u8<BRA: BlindRotationAlgo, BE: Backend>(test_context: &TestContext<BRA, BE>)

poulpy-schemes/src/tfhe/bdd_arithmetic/tests/test_suite/glwe_blind_selection.rs

@@ -129,7 +129,7 @@ where
         res.decrypt(module, &mut pt, sk_glwe_prep, scratch.borrow());
 
         let idx = ((k >> bit_start) & mask) as usize;
-        if idx.is_multiple_of(3) {
+        if !idx.is_multiple_of(3) {
             assert_eq!(0, pt.decode_coeff_i64(TorusPrecision(base2k.as_u32()), 0));
         } else {
             assert_eq!(