1use itertools::izip;
  2
  3#[cfg(target_arch = "x86_64")]
  4use poulpy_cpu_avx::FFT64Avx as BackendImpl;
  5#[cfg(not(target_arch = "x86_64"))]
  6use poulpy_cpu_ref::FFT64Ref as BackendImpl;
  7
  8use poulpy_hal::{
  9    api::{
 10        ModuleNew, ScratchOwnedAlloc, ScratchOwnedBorrow, SvpApplyDftToDftInplace, SvpPPolAlloc, SvpPrepare, VecZnxAddNormal,
 11        VecZnxBigAddSmallInplace, VecZnxBigAlloc, VecZnxBigNormalize, VecZnxBigNormalizeTmpBytes, VecZnxBigSubSmallNegateInplace,
 12        VecZnxDftAlloc, VecZnxDftApply, VecZnxFillUniform, VecZnxIdftApplyTmpA, VecZnxNormalizeInplace,
 13    },
 14    layouts::{Module, ScalarZnx, ScratchOwned, SvpPPol, VecZnx, VecZnxBig, VecZnxDft, ZnxInfos},
 15    source::Source,
 16};
 17
 18fn main() {
 19    let n: usize = 16;
 20    let base2k: usize = 18;
 21    let ct_size: usize = 3;
 22    let msg_size: usize = 2;
 23    let log_scale: usize = msg_size * base2k - 5;
 24    let module: Module<BackendImpl> = Module::<BackendImpl>::new(n as u64);
 25
 26    let mut scratch: ScratchOwned<BackendImpl> = ScratchOwned::<BackendImpl>::alloc(module.vec_znx_big_normalize_tmp_bytes());
 27
 28    let seed: [u8; 32] = [0; 32];
 29    let mut source: Source = Source::new(seed);
 30
 31    // s <- Z_{-1, 0, 1}[X]/(X^{N}+1)
 32    let mut s: ScalarZnx<Vec<u8>> = ScalarZnx::alloc(module.n(), 1);
 33    s.fill_ternary_prob(0, 0.5, &mut source);
 34
 35    // Buffer to store s in the DFT domain
 36    let mut s_dft: SvpPPol<Vec<u8>, BackendImpl> = module.svp_ppol_alloc(s.cols());
 37
 38    // s_dft <- DFT(s)
 39    module.svp_prepare(&mut s_dft, 0, &s, 0);
 40
 41    // Allocates a VecZnx with two columns: ct=(0, 0)
 42    let mut ct: VecZnx<Vec<u8>> = VecZnx::alloc(
 43        module.n(),
 44        2,       // Number of columns
 45        ct_size, // Number of small poly per column
 46    );
 47
 48    // Fill the second column with random values: ct = (0, a)
 49    module.vec_znx_fill_uniform(base2k, &mut ct, 1, &mut source);
 50
 51    let mut buf_dft: VecZnxDft<Vec<u8>, BackendImpl> = module.vec_znx_dft_alloc(1, ct_size);
 52
 53    module.vec_znx_dft_apply(1, 0, &mut buf_dft, 0, &ct, 1);
 54
 55    // Applies DFT(ct[1]) * DFT(s)
 56    module.svp_apply_dft_to_dft_inplace(
 57        &mut buf_dft, // DFT(ct[1] * s)
 58        0,            // Selects the first column of res
 59        &s_dft,       // DFT(s)
 60        0,            // Selects the first column of s_dft
 61    );
 62
 63    // Alias scratch space (VecZnxDft<B> is always at least as big as VecZnxBig<B>)
 64
 65    // BIG(ct[1] * s) <- IDFT(DFT(ct[1] * s)) (not normalized)
 66    let mut buf_big: VecZnxBig<Vec<u8>, BackendImpl> = module.vec_znx_big_alloc(1, ct_size);
 67    module.vec_znx_idft_apply_tmpa(&mut buf_big, 0, &mut buf_dft, 0);
 68
 69    // Creates a plaintext: VecZnx with 1 column
 70    let mut m = VecZnx::alloc(
 71        module.n(),
 72        1,        // Number of columns
 73        msg_size, // Number of small polynomials
 74    );
 75    let mut want: Vec<i64> = vec![0; n];
 76    want.iter_mut()
 77        .for_each(|x| *x = source.next_u64n(16, 15) as i64);
 78    m.encode_vec_i64(base2k, 0, log_scale, &want);
 79    module.vec_znx_normalize_inplace(base2k, &mut m, 0, scratch.borrow());
 80
 81    // m - BIG(ct[1] * s)
 82    module.vec_znx_big_sub_small_negate_inplace(
 83        &mut buf_big,
 84        0, // Selects the first column of the receiver
 85        &m,
 86        0, // Selects the first column of the message
 87    );
 88
 89    // Normalizes back to VecZnx
 90    // ct[0] <- m - BIG(c1 * s)
 91    module.vec_znx_big_normalize(
 92        base2k,
 93        &mut ct,
 94        0, // Selects the first column of ct (ct[0])
 95        base2k,
 96        &buf_big,
 97        0, // Selects the first column of buf_big
 98        scratch.borrow(),
 99    );
100
101    // Add noise to ct[0]
102    // ct[0] <- ct[0] + e
103    module.vec_znx_add_normal(
104        base2k,
105        &mut ct,
106        0,                // Selects the first column of ct (ct[0])
107        base2k * ct_size, // Scaling of the noise: 2^{-base2k * limbs}
108        &mut source,
109        3.2,       // Standard deviation
110        3.2 * 6.0, // Truncatation bound
111    );
112
113    // Final ciphertext: ct = (-a * s + m + e, a)
114
115    // Decryption
116
117    // DFT(ct[1] * s)
118    module.vec_znx_dft_apply(1, 0, &mut buf_dft, 0, &ct, 1);
119    module.svp_apply_dft_to_dft_inplace(
120        &mut buf_dft,
121        0, // Selects the first column of res.
122        &s_dft,
123        0,
124    );
125
126    // BIG(c1 * s) = IDFT(DFT(c1 * s))
127    module.vec_znx_idft_apply_tmpa(&mut buf_big, 0, &mut buf_dft, 0);
128
129    // BIG(c1 * s) + ct[0]
130    module.vec_znx_big_add_small_inplace(&mut buf_big, 0, &ct, 0);
131
132    // m + e <- BIG(ct[1] * s + ct[0])
133    let mut res = VecZnx::alloc(module.n(), 1, ct_size);
134    module.vec_znx_big_normalize(base2k, &mut res, 0, base2k, &buf_big, 0, scratch.borrow());
135
136    // have = m * 2^{log_scale} + e
137    let mut have: Vec<i64> = vec![i64::default(); n];
138    res.decode_vec_i64(base2k, 0, ct_size * base2k, &mut have);
139    let scale: f64 = (1 << (res.size() * base2k - log_scale)) as f64;
140    izip!(want.iter(), have.iter())
141        .enumerate()
142        .for_each(|(i, (a, b))| {
143            println!("{}: {} {}", i, a, (*b as f64) / scale);
144        });
145}
146