poulpy_core/keyswitching/
ggsw_ct.rs

1use poulpy_hal::{
2    api::{
3        DFT, IDFTConsume, IDFTTmpA, ScratchAvailable, TakeVecZnxBig, TakeVecZnxDft, VecZnxBigAddSmallInplace,
4        VecZnxBigAllocBytes, VecZnxBigNormalize, VecZnxBigNormalizeTmpBytes, VecZnxCopy, VecZnxDftAddInplace,
5        VecZnxDftAllocBytes, VecZnxDftCopy, VecZnxNormalizeTmpBytes, VmpApplyDftToDft, VmpApplyDftToDftAdd,
6        VmpApplyDftToDftTmpBytes,
7    },
8    layouts::{Backend, DataMut, DataRef, Module, Scratch, VecZnx, VmpPMat, ZnxInfos},
9};
10
11use crate::{
12    layouts::{
13        GGLWECiphertext, GGSWCiphertext, GLWECiphertext, Infos,
14        prepared::{GGLWESwitchingKeyPrepared, GGLWETensorKeyPrepared},
15    },
16    operations::GLWEOperations,
17};
18
19impl GGSWCiphertext<Vec<u8>> {
20    pub(crate) fn expand_row_scratch_space<B: Backend>(
21        module: &Module<B>,
22        basek: usize,
23        self_k: usize,
24        k_tsk: usize,
25        digits: usize,
26        rank: usize,
27    ) -> usize
28    where
29        Module<B>: VecZnxDftAllocBytes + VmpApplyDftToDftTmpBytes + VecZnxBigAllocBytes + VecZnxNormalizeTmpBytes,
30    {
31        let tsk_size: usize = k_tsk.div_ceil(basek);
32        let self_size_out: usize = self_k.div_ceil(basek);
33        let self_size_in: usize = self_size_out.div_ceil(digits);
34
35        let tmp_dft_i: usize = module.vec_znx_dft_alloc_bytes(rank + 1, tsk_size);
36        let tmp_a: usize = module.vec_znx_dft_alloc_bytes(1, self_size_in);
37        let vmp: usize = module.vmp_apply_dft_to_dft_tmp_bytes(
38            self_size_out,
39            self_size_in,
40            self_size_in,
41            rank,
42            rank,
43            tsk_size,
44        );
45        let tmp_idft: usize = module.vec_znx_big_alloc_bytes(1, tsk_size);
46        let norm: usize = module.vec_znx_normalize_tmp_bytes();
47        tmp_dft_i + ((tmp_a + vmp) | (tmp_idft + norm))
48    }
49
50    #[allow(clippy::too_many_arguments)]
51    pub fn keyswitch_scratch_space<B: Backend>(
52        module: &Module<B>,
53        basek: usize,
54        k_out: usize,
55        k_in: usize,
56        k_ksk: usize,
57        digits_ksk: usize,
58        k_tsk: usize,
59        digits_tsk: usize,
60        rank: usize,
61    ) -> usize
62    where
63        Module<B>: VecZnxDftAllocBytes
64            + VmpApplyDftToDftTmpBytes
65            + VecZnxBigAllocBytes
66            + VecZnxNormalizeTmpBytes
67            + VecZnxBigNormalizeTmpBytes,
68    {
69        let out_size: usize = k_out.div_ceil(basek);
70        let res_znx: usize = VecZnx::alloc_bytes(module.n(), rank + 1, out_size);
71        let ci_dft: usize = module.vec_znx_dft_alloc_bytes(rank + 1, out_size);
72        let ks: usize = GLWECiphertext::keyswitch_scratch_space(module, basek, k_out, k_in, k_ksk, digits_ksk, rank, rank);
73        let expand_rows: usize = GGSWCiphertext::expand_row_scratch_space(module, basek, k_out, k_tsk, digits_tsk, rank);
74        let res_dft: usize = module.vec_znx_dft_alloc_bytes(rank + 1, out_size);
75        res_znx + ci_dft + (ks | expand_rows | res_dft)
76    }
77
78    #[allow(clippy::too_many_arguments)]
79    pub fn keyswitch_inplace_scratch_space<B: Backend>(
80        module: &Module<B>,
81        basek: usize,
82        k_out: usize,
83        k_ksk: usize,
84        digits_ksk: usize,
85        k_tsk: usize,
86        digits_tsk: usize,
87        rank: usize,
88    ) -> usize
89    where
90        Module<B>: VecZnxDftAllocBytes
91            + VmpApplyDftToDftTmpBytes
92            + VecZnxBigAllocBytes
93            + VecZnxNormalizeTmpBytes
94            + VecZnxBigNormalizeTmpBytes,
95    {
96        GGSWCiphertext::keyswitch_scratch_space(
97            module, basek, k_out, k_out, k_ksk, digits_ksk, k_tsk, digits_tsk, rank,
98        )
99    }
100}
101
102impl<DataSelf: DataMut> GGSWCiphertext<DataSelf> {
103    pub fn from_gglwe<DataA, DataTsk, B: Backend>(
104        &mut self,
105        module: &Module<B>,
106        a: &GGLWECiphertext<DataA>,
107        tsk: &GGLWETensorKeyPrepared<DataTsk, B>,
108        scratch: &mut Scratch<B>,
109    ) where
110        DataA: DataRef,
111        DataTsk: DataRef,
112        Module<B>: VecZnxCopy
113            + VecZnxDftAllocBytes
114            + VmpApplyDftToDftTmpBytes
115            + VecZnxBigAllocBytes
116            + VecZnxNormalizeTmpBytes
117            + DFT<B>
118            + VecZnxDftCopy<B>
119            + VmpApplyDftToDft<B>
120            + VmpApplyDftToDftAdd<B>
121            + VecZnxDftAddInplace<B>
122            + VecZnxBigNormalize<B>
123            + IDFTTmpA<B>,
124        Scratch<B>: ScratchAvailable + TakeVecZnxDft<B> + TakeVecZnxBig<B>,
125    {
126        #[cfg(debug_assertions)]
127        {
128            assert_eq!(self.rank(), a.rank());
129            assert_eq!(self.rows(), a.rows());
130            assert_eq!(self.n(), module.n());
131            assert_eq!(a.n(), module.n());
132            assert_eq!(tsk.n(), module.n());
133        }
134        (0..self.rows()).for_each(|row_i| {
135            self.at_mut(row_i, 0).copy(module, &a.at(row_i, 0));
136        });
137        self.expand_row(module, tsk, scratch);
138    }
139
140    pub fn keyswitch<DataLhs: DataRef, DataKsk: DataRef, DataTsk: DataRef, B: Backend>(
141        &mut self,
142        module: &Module<B>,
143        lhs: &GGSWCiphertext<DataLhs>,
144        ksk: &GGLWESwitchingKeyPrepared<DataKsk, B>,
145        tsk: &GGLWETensorKeyPrepared<DataTsk, B>,
146        scratch: &mut Scratch<B>,
147    ) where
148        Module<B>: VecZnxDftAllocBytes
149            + VmpApplyDftToDftTmpBytes
150            + VecZnxBigNormalizeTmpBytes
151            + VmpApplyDftToDft<B>
152            + VmpApplyDftToDftAdd<B>
153            + DFT<B>
154            + IDFTConsume<B>
155            + VecZnxBigAddSmallInplace<B>
156            + VecZnxBigNormalize<B>
157            + VecZnxDftAllocBytes
158            + VecZnxBigAllocBytes
159            + VecZnxNormalizeTmpBytes
160            + VecZnxDftCopy<B>
161            + VecZnxDftAddInplace<B>
162            + IDFTTmpA<B>,
163        Scratch<B>: ScratchAvailable + TakeVecZnxDft<B> + TakeVecZnxBig<B>,
164    {
165        self.keyswitch_internal(module, lhs, ksk, scratch);
166        self.expand_row(module, tsk, scratch);
167    }
168
169    pub fn keyswitch_inplace<DataKsk: DataRef, DataTsk: DataRef, B: Backend>(
170        &mut self,
171        module: &Module<B>,
172        ksk: &GGLWESwitchingKeyPrepared<DataKsk, B>,
173        tsk: &GGLWETensorKeyPrepared<DataTsk, B>,
174        scratch: &mut Scratch<B>,
175    ) where
176        Module<B>: VecZnxDftAllocBytes
177            + VmpApplyDftToDftTmpBytes
178            + VecZnxBigNormalizeTmpBytes
179            + VmpApplyDftToDft<B>
180            + VmpApplyDftToDftAdd<B>
181            + DFT<B>
182            + IDFTConsume<B>
183            + VecZnxBigAddSmallInplace<B>
184            + VecZnxBigNormalize<B>
185            + VecZnxDftAllocBytes
186            + VecZnxBigAllocBytes
187            + VecZnxNormalizeTmpBytes
188            + VecZnxDftCopy<B>
189            + VecZnxDftAddInplace<B>
190            + IDFTTmpA<B>,
191        Scratch<B>: ScratchAvailable + TakeVecZnxDft<B> + TakeVecZnxBig<B>,
192    {
193        unsafe {
194            let self_ptr: *mut GGSWCiphertext<DataSelf> = self as *mut GGSWCiphertext<DataSelf>;
195            self.keyswitch(module, &*self_ptr, ksk, tsk, scratch);
196        }
197    }
198
199    pub fn expand_row<DataTsk: DataRef, B: Backend>(
200        &mut self,
201        module: &Module<B>,
202        tsk: &GGLWETensorKeyPrepared<DataTsk, B>,
203        scratch: &mut Scratch<B>,
204    ) where
205        Module<B>: VecZnxDftAllocBytes
206            + VmpApplyDftToDftTmpBytes
207            + VecZnxBigAllocBytes
208            + VecZnxNormalizeTmpBytes
209            + DFT<B>
210            + VecZnxDftCopy<B>
211            + VmpApplyDftToDft<B>
212            + VmpApplyDftToDftAdd<B>
213            + VecZnxDftAddInplace<B>
214            + VecZnxBigNormalize<B>
215            + IDFTTmpA<B>,
216        Scratch<B>: ScratchAvailable + TakeVecZnxDft<B> + TakeVecZnxBig<B>,
217    {
218        assert!(
219            scratch.available()
220                >= GGSWCiphertext::expand_row_scratch_space(
221                    module,
222                    self.basek(),
223                    self.k(),
224                    tsk.k(),
225                    tsk.digits(),
226                    tsk.rank()
227                )
228        );
229
230        let n: usize = self.n();
231        let rank: usize = self.rank();
232        let cols: usize = rank + 1;
233
234        // Keyswitch the j-th row of the col 0
235        (0..self.rows()).for_each(|row_i| {
236            // Pre-compute DFT of (a0, a1, a2)
237            let (mut ci_dft, scratch1) = scratch.take_vec_znx_dft(n, cols, self.size());
238            (0..cols).for_each(|i| {
239                module.dft(1, 0, &mut ci_dft, i, &self.at(row_i, 0).data, i);
240            });
241
242            (1..cols).for_each(|col_j| {
243                // Example for rank 3:
244                //
245                // Note: M is a vector (m, Bm, B^2m, B^3m, ...), so each column is
246                // actually composed of that many rows and we focus on a specific row here
247                // implicitely given ci_dft.
248                //
249                // # Input
250                //
251                // col 0: (-(a0s0 + a1s1 + a2s2) + M[i], a0    , a1    , a2    )
252                // col 1: (0, 0, 0, 0)
253                // col 2: (0, 0, 0, 0)
254                // col 3: (0, 0, 0, 0)
255                //
256                // # Output
257                //
258                // col 0: (-(a0s0 + a1s1 + a2s2) + M[i], a0       , a1       , a2       )
259                // col 1: (-(b0s0 + b1s1 + b2s2)       , b0 + M[i], b1       , b2       )
260                // col 2: (-(c0s0 + c1s1 + c2s2)       , c0       , c1 + M[i], c2       )
261                // col 3: (-(d0s0 + d1s1 + d2s2)       , d0       , d1       , d2 + M[i])
262
263                let digits: usize = tsk.digits();
264
265                let (mut tmp_dft_i, scratch2) = scratch1.take_vec_znx_dft(n, cols, tsk.size());
266                let (mut tmp_a, scratch3) = scratch2.take_vec_znx_dft(n, 1, ci_dft.size().div_ceil(digits));
267
268                {
269                    // Performs a key-switch for each combination of s[i]*s[j], i.e. for a0, a1, a2
270                    //
271                    // # Example for col=1
272                    //
273                    // a0 * (-(f0s0 + f1s1 + f1s2) + s0^2, f0, f1, f2) = (-(a0f0s0 + a0f1s1 + a0f1s2) + a0s0^2, a0f0, a0f1, a0f2)
274                    // +
275                    // a1 * (-(g0s0 + g1s1 + g1s2) + s0s1, g0, g1, g2) = (-(a1g0s0 + a1g1s1 + a1g1s2) + a1s0s1, a1g0, a1g1, a1g2)
276                    // +
277                    // a2 * (-(h0s0 + h1s1 + h1s2) + s0s2, h0, h1, h2) = (-(a2h0s0 + a2h1s1 + a2h1s2) + a2s0s2, a2h0, a2h1, a2h2)
278                    // =
279                    // (-(x0s0 + x1s1 + x2s2) + s0(a0s0 + a1s1 + a2s2), x0, x1, x2)
280                    (1..cols).for_each(|col_i| {
281                        let pmat: &VmpPMat<DataTsk, B> = &tsk.at(col_i - 1, col_j - 1).key.data; // Selects Enc(s[i]s[j])
282
283                        // Extracts a[i] and multipies with Enc(s[i]s[j])
284                        (0..digits).for_each(|di| {
285                            tmp_a.set_size((ci_dft.size() + di) / digits);
286
287                            // Small optimization for digits > 2
288                            // VMP produce some error e, and since we aggregate vmp * 2^{di * B}, then
289                            // we also aggregate ei * 2^{di * B}, with the largest error being ei * 2^{(digits-1) * B}.
290                            // As such we can ignore the last digits-2 limbs safely of the sum of vmp products.
291                            // It is possible to further ignore the last digits-1 limbs, but this introduce
292                            // ~0.5 to 1 bit of additional noise, and thus not chosen here to ensure that the same
293                            // noise is kept with respect to the ideal functionality.
294                            tmp_dft_i.set_size(tsk.size() - ((digits - di) as isize - 2).max(0) as usize);
295
296                            module.vec_znx_dft_copy(digits, digits - 1 - di, &mut tmp_a, 0, &ci_dft, col_i);
297                            if di == 0 && col_i == 1 {
298                                module.vmp_apply_dft_to_dft(&mut tmp_dft_i, &tmp_a, pmat, scratch3);
299                            } else {
300                                module.vmp_apply_dft_to_dft_add(&mut tmp_dft_i, &tmp_a, pmat, di, scratch3);
301                            }
302                        });
303                    });
304                }
305
306                // Adds -(sum a[i] * s[i]) + m)  on the i-th column of tmp_idft_i
307                //
308                // (-(x0s0 + x1s1 + x2s2) + a0s0s0 + a1s0s1 + a2s0s2, x0, x1, x2)
309                // +
310                // (0, -(a0s0 + a1s1 + a2s2) + M[i], 0, 0)
311                // =
312                // (-(x0s0 + x1s1 + x2s2) + s0(a0s0 + a1s1 + a2s2), x0 -(a0s0 + a1s1 + a2s2) + M[i], x1, x2)
313                // =
314                // (-(x0s0 + x1s1 + x2s2), x0 + M[i], x1, x2)
315                module.vec_znx_dft_add_inplace(&mut tmp_dft_i, col_j, &ci_dft, 0);
316                let (mut tmp_idft, scratch3) = scratch2.take_vec_znx_big(n, 1, tsk.size());
317                (0..cols).for_each(|i| {
318                    module.idft_tmp_a(&mut tmp_idft, 0, &mut tmp_dft_i, i);
319                    module.vec_znx_big_normalize(
320                        self.basek(),
321                        &mut self.at_mut(row_i, col_j).data,
322                        i,
323                        &tmp_idft,
324                        0,
325                        scratch3,
326                    );
327                });
328            })
329        })
330    }
331
332    fn keyswitch_internal<DataLhs: DataRef, DataKsk: DataRef, B: Backend>(
333        &mut self,
334        module: &Module<B>,
335        lhs: &GGSWCiphertext<DataLhs>,
336        ksk: &GGLWESwitchingKeyPrepared<DataKsk, B>,
337        scratch: &mut Scratch<B>,
338    ) where
339        Module<B>: VecZnxDftAllocBytes
340            + VmpApplyDftToDftTmpBytes
341            + VecZnxBigNormalizeTmpBytes
342            + VmpApplyDftToDft<B>
343            + VmpApplyDftToDftAdd<B>
344            + DFT<B>
345            + IDFTConsume<B>
346            + VecZnxBigAddSmallInplace<B>
347            + VecZnxBigNormalize<B>,
348        Scratch<B>: ScratchAvailable + TakeVecZnxDft<B>,
349    {
350        // Keyswitch the j-th row of the col 0
351        (0..lhs.rows()).for_each(|row_i| {
352            // Key-switch column 0, i.e.
353            // col 0: (-(a0s0 + a1s1 + a2s2) + M[i], a0, a1, a2) -> (-(a0s0' + a1s1' + a2s2') + M[i], a0, a1, a2)
354            self.at_mut(row_i, 0)
355                .keyswitch(module, &lhs.at(row_i, 0), ksk, scratch);
356        })
357    }
358}
poulpy_core/keyswitching/ggsw_ct.rs

poulpy_core/keyswitching/
ggsw_ct.rs
