Dev serialization (#64)

* Added compressed serialization for GLWECiphertext + Ciphertext decompression

* Added compressed serialization for GGLWECiphertext & GLWESwitchingkey

* generalized automorphism test

* Removed ops on scalar_znx, replaced by as_vec_znx/as_vec_znx_mut and then call op on vec_znx

* Added tests for automorphism key encryption

* Added tensorkey compressed

* added ggsw compressed

backend/src/hal/tests/mod.rs

@@ -1 +1,2 @@
+pub mod serialization;
 pub mod vec_znx;

backend/src/hal/tests/serialization.rs

@@ -0,0 +1,56 @@
+use std::fmt::Debug;
+
+use sampling::source::Source;
+
+use crate::hal::{
+    api::{FillUniform, ZnxZero},
+    layouts::{ReaderFrom, WriterTo},
+};
+
+/// Generic test for serialization and deserialization.
+///
+/// - `T` must implement I/O traits, zeroing, cloning, and random filling.
+pub fn test_reader_writer_interface<T>(mut original: T)
+where
+    T: WriterTo + ReaderFrom + PartialEq + Eq + Debug + Clone + ZnxZero + FillUniform,
+{
+    // Fill original with uniform random data
+    let mut source = Source::new([0u8; 32]);
+    original.fill_uniform(&mut source);
+
+    // Serialize into a buffer
+    let mut buffer = Vec::new();
+    original.write_to(&mut buffer).expect("write_to failed");
+
+    // Prepare receiver: same shape, but zeroed
+    let mut receiver = original.clone();
+    receiver.zero();
+
+    // Deserialize from buffer
+    let mut reader: &[u8] = &buffer;
+    receiver.read_from(&mut reader).expect("read_from failed");
+
+    // Ensure serialization round-trip correctness
+    assert_eq!(
+        &original, &receiver,
+        "Deserialized object does not match the original"
+    );
+}
+
+#[test]
+fn scalar_znx_serialize() {
+    let original: crate::hal::layouts::ScalarZnx<Vec<u8>> = crate::hal::layouts::ScalarZnx::alloc(1024, 3);
+    test_reader_writer_interface(original);
+}
+
+#[test]
+fn vec_znx_serialize() {
+    let original: crate::hal::layouts::VecZnx<Vec<u8>> = crate::hal::layouts::VecZnx::alloc::<i64>(1024, 3, 4);
+    test_reader_writer_interface(original);
+}
+
+#[test]
+fn mat_znx_serialize() {
+    let original: crate::hal::layouts::MatZnx<Vec<u8>> = crate::hal::layouts::MatZnx::alloc(1024, 3, 2, 2, 4);
+    test_reader_writer_interface(original);
+}