wip rlwe + some bug fixes in base2k

rlwe/src/decryptor.rs

@@ -0,0 +1,80 @@
+use crate::{
+    ciphertext::Ciphertext, keys::SecretKey, parameters::Parameters, plaintext::Plaintext,
+};
+use base2k::{Module, SvpPPol, SvpPPolOps, VecZnxDft};
+use std::cmp::min;
+
+pub struct Decryptor {
+    sk: SvpPPol,
+}
+
+impl Decryptor {
+    pub fn new(params: &Parameters, sk: &SecretKey) -> Self {
+        let mut sk_svp_ppol: SvpPPol = params.module().svp_new_ppol();
+        sk.prepare(params.module(), &mut sk_svp_ppol);
+        Self { sk: sk_svp_ppol }
+    }
+}
+
+pub fn decrypt_rlwe_thread_safe_tmp_byte(module: &Module, limbs: usize) -> usize {
+    module.bytes_of_vec_znx_dft(limbs) + module.vec_znx_big_normalize_tmp_bytes()
+}
+
+impl Parameters {
+    pub fn decrypt_rlwe_thread_safe_tmp_byte(&self, log_q: usize) -> usize {
+        decrypt_rlwe_thread_safe_tmp_byte(
+            self.module(),
+            (log_q + self.log_base2k() - 1) / self.log_base2k(),
+        )
+    }
+
+    pub fn decrypt_rlwe_thread_safe(
+        &self,
+        res: &mut Plaintext,
+        ct: &Ciphertext,
+        sk: &SvpPPol,
+        tmp_bytes: &mut [u8],
+    ) {
+        decrypt_rlwe_thread_safe(self.module(), res, ct, sk, tmp_bytes)
+    }
+}
+
+pub fn decrypt_rlwe_thread_safe(
+    module: &Module,
+    res: &mut Plaintext,
+    ct: &Ciphertext,
+    sk: &SvpPPol,
+    tmp_bytes: &mut [u8],
+) {
+    let limbs: usize = min(res.limbs(), ct.limbs());
+
+    assert!(
+        tmp_bytes.len() >= decrypt_rlwe_thread_safe_tmp_byte(module, limbs),
+        "invalid tmp_bytes: tmp_bytes.len()={} < decrypt_rlwe_thread_safe_tmp_byte={}",
+        tmp_bytes.len(),
+        decrypt_rlwe_thread_safe_tmp_byte(module, limbs)
+    );
+
+    let res_dft_bytes: usize = module.bytes_of_vec_znx_dft(limbs);
+
+    let mut res_dft: VecZnxDft = VecZnxDft::from_bytes(limbs, tmp_bytes);
+    let mut res_big: base2k::VecZnxBig = res_dft.as_vec_znx_big();
+
+    // res_dft <- DFT(ct[1]) * DFT(sk)
+    module.svp_apply_dft(&mut res_dft, sk, &ct.0.value[1], limbs);
+    // res_big <- ct[1] x sk
+    module.vec_znx_idft_tmp_a(&mut res_big, &mut res_dft, limbs);
+    // res_big <- ct[1] x sk + ct[0]
+    module.vec_znx_big_add_small_inplace(&mut res_big, &ct.0.value[0], limbs);
+    // res <- normalize(ct[1] x sk + ct[0])
+    module.vec_znx_big_normalize(
+        ct.log_base2k(),
+        res.at_mut(0),
+        &res_big,
+        &mut tmp_bytes[res_dft_bytes..],
+    );
+
+    res.0.log_base2k = ct.log_base2k();
+    res.0.log_q = min(res.log_q(), ct.log_q());
+    res.0.log_scale = ct.log_scale();
+}