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use crate::integer::{CrtCiphertext, ServerKey};
use crate::shortint::CheckError;
impl ServerKey {
/// Computes homomorphically an addition between two ciphertexts encrypting integer values.
///
/// # Example
///
///```rust
/// use tfhe::integer::gen_keys_crt;
/// use tfhe::shortint::parameters::PARAM_MESSAGE_3_CARRY_3_KS_PBS_GAUSSIAN_2M128;
///
/// // Generate the client key and the server key:
/// let basis = vec![2, 3, 5];
/// let modulus: u64 = basis.iter().product();
/// let (cks, sks) = gen_keys_crt(PARAM_MESSAGE_3_CARRY_3_KS_PBS_GAUSSIAN_2M128, basis);
///
/// let clear_1 = 14;
/// let clear_2 = 14;
/// // Encrypt two messages
/// let mut ctxt_1 = cks.encrypt(clear_1);
/// let mut ctxt_2 = cks.encrypt(clear_2);
///
/// sks.smart_crt_add_assign(&mut ctxt_1, &mut ctxt_2);
///
/// // Decrypt
/// let res = cks.decrypt(&ctxt_1);
/// assert_eq!((clear_1 + clear_2) % modulus, res);
/// ```
pub fn smart_crt_add(
&self,
ct_left: &mut CrtCiphertext,
ct_right: &mut CrtCiphertext,
) -> CrtCiphertext {
if self.is_crt_add_possible(ct_left, ct_right).is_err() {
self.full_extract_message_assign(ct_left);
self.full_extract_message_assign(ct_right);
}
self.is_crt_add_possible(ct_left, ct_right).unwrap();
self.unchecked_crt_add(ct_left, ct_right)
}
pub fn smart_crt_add_assign(&self, ct_left: &mut CrtCiphertext, ct_right: &mut CrtCiphertext) {
//If the ciphertext cannot be added together without exceeding the capacity of a ciphertext
if self.is_crt_add_possible(ct_left, ct_right).is_err() {
self.full_extract_message_assign(ct_left);
self.full_extract_message_assign(ct_right);
}
self.is_crt_add_possible(ct_left, ct_right).unwrap();
self.unchecked_crt_add_assign(ct_left, ct_right);
}
pub fn is_crt_add_possible(
&self,
ct_left: &CrtCiphertext,
ct_right: &CrtCiphertext,
) -> Result<(), CheckError> {
for (ct_left_i, ct_right_i) in ct_left.blocks.iter().zip(ct_right.blocks.iter()) {
self.key
.is_add_possible(ct_left_i.noise_degree(), ct_right_i.noise_degree())?;
}
Ok(())
}
pub fn unchecked_crt_add_assign(&self, ct_left: &mut CrtCiphertext, ct_right: &CrtCiphertext) {
for (ct_left_i, ct_right_i) in ct_left.blocks.iter_mut().zip(ct_right.blocks.iter()) {
self.key.unchecked_add_assign(ct_left_i, ct_right_i);
}
}
pub fn unchecked_crt_add(
&self,
ct_left: &CrtCiphertext,
ct_right: &CrtCiphertext,
) -> CrtCiphertext {
let mut ct_res = ct_left.clone();
self.unchecked_crt_add_assign(&mut ct_res, ct_right);
ct_res
}
}