Re-add serialized size const fn for cipher

src/cipher/cipher.rs

@@ -12,7 +12,9 @@ use dusk_plonk::jubjub::AffinePoint;
 use dusk_plonk::prelude::*;
 use hades252::{ScalarStrategy, Strategy, WIDTH};
 
-use super::{CIPHER_BYTES_SIZE, CIPHER_SIZE, MESSAGE_CAPACITY};
+use super::{
+    CIPHER_BYTES_SIZE, CIPHER_SIZE, ENCRYPTED_DATA_SIZE, MESSAGE_CAPACITY,
+};
 
 pub use super::CipherError;
 
@@ -143,6 +145,11 @@ impl PoseidonCipher {
         MESSAGE_CAPACITY
     }
 
+    /// Bytes consumed on serialization of the poseidon cipher
+    pub const fn serialized_size() -> usize {
+        ENCRYPTED_DATA_SIZE
+    }
+
     /// Encrypt a slice of scalars into an internal cipher representation
     ///
     /// The message size will be truncated to [`MESSAGE_CAPACITY`] bits