1use base2k::{
  2    Encoding, FFT64, Module, Sampling, Scalar, ScalarAlloc, ScalarZnxDft, ScalarZnxDftOps, VecZnx, VecZnxBig, VecZnxBigOps,
  3    VecZnxDft, VecZnxDftOps, VecZnxOps, ZnxInfos, alloc_aligned,
  4};
  5use itertools::izip;
  6use sampling::source::Source;
  7
  8fn main() {
  9    let n: usize = 16;
 10    let log_base2k: usize = 18;
 11    let ct_size: usize = 3;
 12    let msg_size: usize = 2;
 13    let log_scale: usize = msg_size * log_base2k - 5;
 14    let module: Module<FFT64> = Module::<FFT64>::new(n);
 15
 16    let mut tmp_bytes_norm: Vec<u8> = alloc_aligned(module.vec_znx_big_normalize_tmp_bytes());
 17    let mut tmp_bytes_dft = alloc_aligned(module.bytes_of_vec_znx_dft(1, ct_size));
 18
 19    let seed: [u8; 32] = [0; 32];
 20    let mut source: Source = Source::new(seed);
 21
 22    // s <- Z_{-1, 0, 1}[X]/(X^{N}+1)
 23    let mut s: Scalar = module.new_scalar(1);
 24    s.fill_ternary_prob(0, 0.5, &mut source);
 25
 26    // Buffer to store s in the DFT domain
 27    let mut s_dft: ScalarZnxDft<FFT64> = module.new_scalar_znx_dft(s.cols());
 28
 29    // s_dft <- DFT(s)
 30    module.svp_prepare(&mut s_dft, 0, &s, 0);
 31
 32    // Allocates a VecZnx with two columns: ct=(0, 0)
 33    let mut ct: VecZnx = module.new_vec_znx(
 34        2,       // Number of columns
 35        ct_size, // Number of small poly per column
 36    );
 37
 38    // Fill the second column with random values: ct = (0, a)
 39    module.fill_uniform(log_base2k, &mut ct, 1, ct_size, &mut source);
 40
 41    // Scratch space for DFT values
 42    let mut buf_dft: VecZnxDft<FFT64> = module.new_vec_znx_dft_from_bytes_borrow(
 43        1,         // Number of columns
 44        ct.size(), // Number of polynomials per column
 45        &mut tmp_bytes_dft,
 46    );
 47
 48    // Applies DFT(ct[1]) * DFT(s)
 49    module.svp_apply_dft(
 50        &mut buf_dft, // DFT(ct[1] * s)
 51        0,            // Selects the first column of res
 52        &s_dft,       // DFT(s)
 53        0,            // Selects the first column of s_dft
 54        &ct,
 55        1, // Selects the second column of ct
 56    );
 57
 58    // Alias scratch space (VecZnxDft<B> is always at least as big as VecZnxBig<B>)
 59    let mut buf_big: VecZnxBig<FFT64> = buf_dft.alias_as_vec_znx_big();
 60
 61    // BIG(ct[1] * s) <- IDFT(DFT(ct[1] * s)) (not normalized)
 62    module.vec_znx_idft_tmp_a(&mut buf_big, 0, &mut buf_dft, 0);
 63
 64    // Creates a plaintext: VecZnx with 1 column
 65    let mut m: VecZnx = module.new_vec_znx(
 66        1,        // Number of columns
 67        msg_size, // Number of small polynomials
 68    );
 69    let mut want: Vec<i64> = vec![0; n];
 70    want.iter_mut()
 71        .for_each(|x| *x = source.next_u64n(16, 15) as i64);
 72    m.encode_vec_i64(0, log_base2k, log_scale, &want, 4);
 73    m.normalize(log_base2k, 0, &mut tmp_bytes_norm);
 74
 75    // m - BIG(ct[1] * s)
 76    module.vec_znx_big_sub_small_a_inplace(
 77        &mut buf_big,
 78        0, // Selects the first column of the receiver
 79        &m,
 80        0, // Selects the first column of the message
 81    );
 82
 83    // Normalizes back to VecZnx
 84    // ct[0] <- m - BIG(c1 * s)
 85    module.vec_znx_big_normalize(
 86        log_base2k,
 87        &mut ct,
 88        0, // Selects the first column of ct (ct[0])
 89        &buf_big,
 90        0, // Selects the first column of buf_big
 91        &mut tmp_bytes_norm,
 92    );
 93
 94    // Add noise to ct[0]
 95    // ct[0] <- ct[0] + e
 96    module.add_normal(
 97        log_base2k,
 98        &mut ct,
 99        0,                    // Selects the first column of ct (ct[0])
100        log_base2k * ct_size, // Scaling of the noise: 2^{-log_base2k * limbs}
101        &mut source,
102        3.2,  // Standard deviation
103        19.0, // Truncatation bound
104    );
105
106    // Final ciphertext: ct = (-a * s + m + e, a)
107
108    // Decryption
109
110    // DFT(ct[1] * s)
111    module.svp_apply_dft(
112        &mut buf_dft,
113        0, // Selects the first column of res.
114        &s_dft,
115        0,
116        &ct,
117        1, // Selects the second column of ct (ct[1])
118    );
119
120    // BIG(c1 * s) = IDFT(DFT(c1 * s))
121    module.vec_znx_idft_tmp_a(&mut buf_big, 0, &mut buf_dft, 0);
122
123    // BIG(c1 * s) + ct[0]
124    module.vec_znx_big_add_small_inplace(&mut buf_big, 0, &ct, 0);
125
126    // m + e <- BIG(ct[1] * s + ct[0])
127    let mut res: VecZnx = module.new_vec_znx(1, ct_size);
128    module.vec_znx_big_normalize(log_base2k, &mut res, 0, &buf_big, 0, &mut tmp_bytes_norm);
129
130    // have = m * 2^{log_scale} + e
131    let mut have: Vec<i64> = vec![i64::default(); n];
132    res.decode_vec_i64(0, log_base2k, res.size() * log_base2k, &mut have);
133
134    let scale: f64 = (1 << (res.size() * log_base2k - log_scale)) as f64;
135    izip!(want.iter(), have.iter())
136        .enumerate()
137        .for_each(|(i, (a, b))| {
138            println!("{}: {} {}", i, a, (*b as f64) / scale);
139        })
140}