Files
poulpy/poulpy-core/src/keyswitching/ggsw_ct.rs
2025-09-15 16:16:11 +02:00

340 lines
14 KiB
Rust

use poulpy_hal::{
api::{
ScratchAvailable, TakeVecZnxBig, TakeVecZnxDft, VecZnxBigAddSmallInplace, VecZnxBigAllocBytes, VecZnxBigNormalize,
VecZnxBigNormalizeTmpBytes, VecZnxCopy, VecZnxDftAddInplace, VecZnxDftAllocBytes, VecZnxDftApply, VecZnxDftCopy,
VecZnxIdftApplyConsume, VecZnxIdftApplyTmpA, VecZnxNormalizeTmpBytes, VmpApplyDftToDft, VmpApplyDftToDftAdd,
VmpApplyDftToDftTmpBytes,
},
layouts::{Backend, DataMut, DataRef, Module, Scratch, VecZnx, VmpPMat, ZnxInfos},
};
use crate::{
layouts::{
GGLWECiphertext, GGSWCiphertext, GLWECiphertext, Infos,
prepared::{GGLWESwitchingKeyPrepared, GGLWETensorKeyPrepared},
},
operations::GLWEOperations,
};
impl GGSWCiphertext<Vec<u8>> {
pub(crate) fn expand_row_scratch_space<B: Backend>(
module: &Module<B>,
basek: usize,
self_k: usize,
k_tsk: usize,
digits: usize,
rank: usize,
) -> usize
where
Module<B>: VecZnxDftAllocBytes + VmpApplyDftToDftTmpBytes + VecZnxBigAllocBytes + VecZnxNormalizeTmpBytes,
{
let tsk_size: usize = k_tsk.div_ceil(basek);
let self_size_out: usize = self_k.div_ceil(basek);
let self_size_in: usize = self_size_out.div_ceil(digits);
let tmp_dft_i: usize = module.vec_znx_dft_alloc_bytes(rank + 1, tsk_size);
let tmp_a: usize = module.vec_znx_dft_alloc_bytes(1, self_size_in);
let vmp: usize = module.vmp_apply_dft_to_dft_tmp_bytes(
self_size_out,
self_size_in,
self_size_in,
rank,
rank,
tsk_size,
);
let tmp_idft: usize = module.vec_znx_big_alloc_bytes(1, tsk_size);
let norm: usize = module.vec_znx_normalize_tmp_bytes();
tmp_dft_i + ((tmp_a + vmp) | (tmp_idft + norm))
}
#[allow(clippy::too_many_arguments)]
pub fn keyswitch_scratch_space<B: Backend>(
module: &Module<B>,
basek: usize,
k_out: usize,
k_in: usize,
k_ksk: usize,
digits_ksk: usize,
k_tsk: usize,
digits_tsk: usize,
rank: usize,
) -> usize
where
Module<B>: VecZnxDftAllocBytes
+ VmpApplyDftToDftTmpBytes
+ VecZnxBigAllocBytes
+ VecZnxNormalizeTmpBytes
+ VecZnxBigNormalizeTmpBytes,
{
let out_size: usize = k_out.div_ceil(basek);
let res_znx: usize = VecZnx::alloc_bytes(module.n(), rank + 1, out_size);
let ci_dft: usize = module.vec_znx_dft_alloc_bytes(rank + 1, out_size);
let ks: usize = GLWECiphertext::keyswitch_scratch_space(module, basek, k_out, k_in, k_ksk, digits_ksk, rank, rank);
let expand_rows: usize = GGSWCiphertext::expand_row_scratch_space(module, basek, k_out, k_tsk, digits_tsk, rank);
let res_dft: usize = module.vec_znx_dft_alloc_bytes(rank + 1, out_size);
res_znx + ci_dft + (ks | expand_rows | res_dft)
}
#[allow(clippy::too_many_arguments)]
pub fn keyswitch_inplace_scratch_space<B: Backend>(
module: &Module<B>,
basek: usize,
k_out: usize,
k_ksk: usize,
digits_ksk: usize,
k_tsk: usize,
digits_tsk: usize,
rank: usize,
) -> usize
where
Module<B>: VecZnxDftAllocBytes
+ VmpApplyDftToDftTmpBytes
+ VecZnxBigAllocBytes
+ VecZnxNormalizeTmpBytes
+ VecZnxBigNormalizeTmpBytes,
{
GGSWCiphertext::keyswitch_scratch_space(
module, basek, k_out, k_out, k_ksk, digits_ksk, k_tsk, digits_tsk, rank,
)
}
}
impl<DataSelf: DataMut> GGSWCiphertext<DataSelf> {
pub fn from_gglwe<DataA, DataTsk, B: Backend>(
&mut self,
module: &Module<B>,
a: &GGLWECiphertext<DataA>,
tsk: &GGLWETensorKeyPrepared<DataTsk, B>,
scratch: &mut Scratch<B>,
) where
DataA: DataRef,
DataTsk: DataRef,
Module<B>: VecZnxCopy
+ VecZnxDftAllocBytes
+ VmpApplyDftToDftTmpBytes
+ VecZnxBigAllocBytes
+ VecZnxNormalizeTmpBytes
+ VecZnxDftApply<B>
+ VecZnxDftCopy<B>
+ VmpApplyDftToDft<B>
+ VmpApplyDftToDftAdd<B>
+ VecZnxDftAddInplace<B>
+ VecZnxBigNormalize<B>
+ VecZnxIdftApplyTmpA<B>,
Scratch<B>: ScratchAvailable + TakeVecZnxDft<B> + TakeVecZnxBig<B>,
{
#[cfg(debug_assertions)]
{
assert_eq!(self.rank(), a.rank());
assert_eq!(self.rows(), a.rows());
assert_eq!(self.n(), module.n());
assert_eq!(a.n(), module.n());
assert_eq!(tsk.n(), module.n());
}
(0..self.rows()).for_each(|row_i| {
self.at_mut(row_i, 0).copy(module, &a.at(row_i, 0));
});
self.expand_row(module, tsk, scratch);
}
pub fn keyswitch<DataLhs: DataRef, DataKsk: DataRef, DataTsk: DataRef, B: Backend>(
&mut self,
module: &Module<B>,
lhs: &GGSWCiphertext<DataLhs>,
ksk: &GGLWESwitchingKeyPrepared<DataKsk, B>,
tsk: &GGLWETensorKeyPrepared<DataTsk, B>,
scratch: &mut Scratch<B>,
) where
Module<B>: VecZnxDftAllocBytes
+ VmpApplyDftToDftTmpBytes
+ VecZnxBigNormalizeTmpBytes
+ VmpApplyDftToDft<B>
+ VmpApplyDftToDftAdd<B>
+ VecZnxDftApply<B>
+ VecZnxIdftApplyConsume<B>
+ VecZnxBigAddSmallInplace<B>
+ VecZnxBigNormalize<B>
+ VecZnxDftAllocBytes
+ VecZnxBigAllocBytes
+ VecZnxNormalizeTmpBytes
+ VecZnxDftCopy<B>
+ VecZnxDftAddInplace<B>
+ VecZnxIdftApplyTmpA<B>,
Scratch<B>: ScratchAvailable + TakeVecZnxDft<B> + TakeVecZnxBig<B>,
{
(0..lhs.rows()).for_each(|row_i| {
// Key-switch column 0, i.e.
// col 0: (-(a0s0 + a1s1 + a2s2) + M[i], a0, a1, a2) -> (-(a0s0' + a1s1' + a2s2') + M[i], a0, a1, a2)
self.at_mut(row_i, 0)
.keyswitch(module, &lhs.at(row_i, 0), ksk, scratch);
});
self.expand_row(module, tsk, scratch);
}
pub fn keyswitch_inplace<DataKsk: DataRef, DataTsk: DataRef, B: Backend>(
&mut self,
module: &Module<B>,
ksk: &GGLWESwitchingKeyPrepared<DataKsk, B>,
tsk: &GGLWETensorKeyPrepared<DataTsk, B>,
scratch: &mut Scratch<B>,
) where
Module<B>: VecZnxDftAllocBytes
+ VmpApplyDftToDftTmpBytes
+ VecZnxBigNormalizeTmpBytes
+ VmpApplyDftToDft<B>
+ VmpApplyDftToDftAdd<B>
+ VecZnxDftApply<B>
+ VecZnxIdftApplyConsume<B>
+ VecZnxBigAddSmallInplace<B>
+ VecZnxBigNormalize<B>
+ VecZnxDftAllocBytes
+ VecZnxBigAllocBytes
+ VecZnxNormalizeTmpBytes
+ VecZnxDftCopy<B>
+ VecZnxDftAddInplace<B>
+ VecZnxIdftApplyTmpA<B>,
Scratch<B>: ScratchAvailable + TakeVecZnxDft<B> + TakeVecZnxBig<B>,
{
(0..self.rows()).for_each(|row_i| {
// Key-switch column 0, i.e.
// col 0: (-(a0s0 + a1s1 + a2s2) + M[i], a0, a1, a2) -> (-(a0s0' + a1s1' + a2s2') + M[i], a0, a1, a2)
self.at_mut(row_i, 0)
.keyswitch_inplace(module, ksk, scratch);
});
self.expand_row(module, tsk, scratch);
}
pub fn expand_row<DataTsk: DataRef, B: Backend>(
&mut self,
module: &Module<B>,
tsk: &GGLWETensorKeyPrepared<DataTsk, B>,
scratch: &mut Scratch<B>,
) where
Module<B>: VecZnxDftAllocBytes
+ VmpApplyDftToDftTmpBytes
+ VecZnxBigAllocBytes
+ VecZnxNormalizeTmpBytes
+ VecZnxDftApply<B>
+ VecZnxDftCopy<B>
+ VmpApplyDftToDft<B>
+ VmpApplyDftToDftAdd<B>
+ VecZnxDftAddInplace<B>
+ VecZnxBigNormalize<B>
+ VecZnxIdftApplyTmpA<B>,
Scratch<B>: ScratchAvailable + TakeVecZnxDft<B> + TakeVecZnxBig<B>,
{
assert!(
scratch.available()
>= GGSWCiphertext::expand_row_scratch_space(
module,
self.basek(),
self.k(),
tsk.k(),
tsk.digits(),
tsk.rank()
)
);
let n: usize = self.n();
let rank: usize = self.rank();
let cols: usize = rank + 1;
// Keyswitch the j-th row of the col 0
(0..self.rows()).for_each(|row_i| {
// Pre-compute DFT of (a0, a1, a2)
let (mut ci_dft, scratch_1) = scratch.take_vec_znx_dft(n, cols, self.size());
(0..cols).for_each(|i| {
module.vec_znx_dft_apply(1, 0, &mut ci_dft, i, &self.at(row_i, 0).data, i);
});
(1..cols).for_each(|col_j| {
// Example for rank 3:
//
// Note: M is a vector (m, Bm, B^2m, B^3m, ...), so each column is
// actually composed of that many rows and we focus on a specific row here
// implicitely given ci_dft.
//
// # Input
//
// col 0: (-(a0s0 + a1s1 + a2s2) + M[i], a0 , a1 , a2 )
// col 1: (0, 0, 0, 0)
// col 2: (0, 0, 0, 0)
// col 3: (0, 0, 0, 0)
//
// # Output
//
// col 0: (-(a0s0 + a1s1 + a2s2) + M[i], a0 , a1 , a2 )
// col 1: (-(b0s0 + b1s1 + b2s2) , b0 + M[i], b1 , b2 )
// col 2: (-(c0s0 + c1s1 + c2s2) , c0 , c1 + M[i], c2 )
// col 3: (-(d0s0 + d1s1 + d2s2) , d0 , d1 , d2 + M[i])
let digits: usize = tsk.digits();
let (mut tmp_dft_i, scratch_2) = scratch_1.take_vec_znx_dft(n, cols, tsk.size());
let (mut tmp_a, scratch_3) = scratch_2.take_vec_znx_dft(n, 1, ci_dft.size().div_ceil(digits));
{
// Performs a key-switch for each combination of s[i]*s[j], i.e. for a0, a1, a2
//
// # Example for col=1
//
// a0 * (-(f0s0 + f1s1 + f1s2) + s0^2, f0, f1, f2) = (-(a0f0s0 + a0f1s1 + a0f1s2) + a0s0^2, a0f0, a0f1, a0f2)
// +
// a1 * (-(g0s0 + g1s1 + g1s2) + s0s1, g0, g1, g2) = (-(a1g0s0 + a1g1s1 + a1g1s2) + a1s0s1, a1g0, a1g1, a1g2)
// +
// a2 * (-(h0s0 + h1s1 + h1s2) + s0s2, h0, h1, h2) = (-(a2h0s0 + a2h1s1 + a2h1s2) + a2s0s2, a2h0, a2h1, a2h2)
// =
// (-(x0s0 + x1s1 + x2s2) + s0(a0s0 + a1s1 + a2s2), x0, x1, x2)
(1..cols).for_each(|col_i| {
let pmat: &VmpPMat<DataTsk, B> = &tsk.at(col_i - 1, col_j - 1).key.data; // Selects Enc(s[i]s[j])
// Extracts a[i] and multipies with Enc(s[i]s[j])
(0..digits).for_each(|di| {
tmp_a.set_size((ci_dft.size() + di) / digits);
// Small optimization for digits > 2
// VMP produce some error e, and since we aggregate vmp * 2^{di * B}, then
// we also aggregate ei * 2^{di * B}, with the largest error being ei * 2^{(digits-1) * B}.
// As such we can ignore the last digits-2 limbs safely of the sum of vmp products.
// It is possible to further ignore the last digits-1 limbs, but this introduce
// ~0.5 to 1 bit of additional noise, and thus not chosen here to ensure that the same
// noise is kept with respect to the ideal functionality.
tmp_dft_i.set_size(tsk.size() - ((digits - di) as isize - 2).max(0) as usize);
module.vec_znx_dft_copy(digits, digits - 1 - di, &mut tmp_a, 0, &ci_dft, col_i);
if di == 0 && col_i == 1 {
module.vmp_apply_dft_to_dft(&mut tmp_dft_i, &tmp_a, pmat, scratch_3);
} else {
module.vmp_apply_dft_to_dft_add(&mut tmp_dft_i, &tmp_a, pmat, di, scratch_3);
}
});
});
}
// Adds -(sum a[i] * s[i]) + m) on the i-th column of tmp_idft_i
//
// (-(x0s0 + x1s1 + x2s2) + a0s0s0 + a1s0s1 + a2s0s2, x0, x1, x2)
// +
// (0, -(a0s0 + a1s1 + a2s2) + M[i], 0, 0)
// =
// (-(x0s0 + x1s1 + x2s2) + s0(a0s0 + a1s1 + a2s2), x0 -(a0s0 + a1s1 + a2s2) + M[i], x1, x2)
// =
// (-(x0s0 + x1s1 + x2s2), x0 + M[i], x1, x2)
module.vec_znx_dft_add_inplace(&mut tmp_dft_i, col_j, &ci_dft, 0);
let (mut tmp_idft, scratch_3) = scratch_2.take_vec_znx_big(n, 1, tsk.size());
(0..cols).for_each(|i| {
module.vec_znx_idft_apply_tmpa(&mut tmp_idft, 0, &mut tmp_dft_i, i);
module.vec_znx_big_normalize(
self.basek(),
&mut self.at_mut(row_i, col_j).data,
i,
&tmp_idft,
0,
scratch_3,
);
});
})
})
}
}