Files
poulpy/base2k/examples/rlwe_encrypt.rs

106 lines
3.1 KiB
Rust

use base2k::{
Encoding, FFT64, Module, Sampling, Scalar, ScalarZnxDft, ScalarZnxDftOps, VecZnx, VecZnxBig, VecZnxBigOps, VecZnxDft,
VecZnxDftOps, VecZnxOps, ZnxInfos, alloc_aligned,
};
use itertools::izip;
use sampling::source::Source;
fn main() {
let n: usize = 16;
let log_base2k: usize = 18;
let ct_size: usize = 3;
let msg_size: usize = 2;
let log_scale: usize = msg_size * log_base2k - 5;
let module: Module<FFT64> = Module::<FFT64>::new(n);
let mut carry: Vec<u8> = alloc_aligned(module.vec_znx_big_normalize_tmp_bytes(2));
let seed: [u8; 32] = [0; 32];
let mut source: Source = Source::new(seed);
// s <- Z_{-1, 0, 1}[X]/(X^{N}+1)
let mut s: Scalar = Scalar::new(n);
s.fill_ternary_prob(0.5, &mut source);
// Buffer to store s in the DFT domain
let mut s_ppol: ScalarZnxDft<FFT64> = module.new_svp_ppol();
// s_ppol <- DFT(s)
module.svp_prepare(&mut s_ppol, &s);
// ct = (c0, c1)
let mut ct: VecZnx = module.new_vec_znx(2, ct_size);
// Fill c1 with random values
module.fill_uniform(log_base2k, &mut ct, 1, ct_size, &mut source);
// Scratch space for DFT values
let mut buf_dft: VecZnxDft<FFT64> = module.new_vec_znx_dft(1, ct.size());
// Applies buf_dft <- s * c1
module.svp_apply_dft(
&mut buf_dft, // DFT(c1 * s)
&s_ppol,
&ct,
1, // c1
);
// Alias scratch space (VecZnxDftis always at least as big as VecZnxBig)
let mut buf_big: VecZnxBig<FFT64> = buf_dft.as_vec_znx_big();
// BIG(c1 * s) <- IDFT(DFT(c1 * s)) (not normalized)
module.vec_znx_idft_tmp_a(&mut buf_big, &mut buf_dft);
// m <- (0)
let mut m: VecZnx = module.new_vec_znx(1, msg_size);
let mut want: Vec<i64> = vec![0; n];
want.iter_mut()
.for_each(|x| *x = source.next_u64n(16, 15) as i64);
m.encode_vec_i64(0, log_base2k, log_scale, &want, 4);
m.normalize(log_base2k, &mut carry);
// m - BIG(c1 * s)
module.vec_znx_big_sub_small_ab_inplace(&mut buf_big, &m);
// c0 <- m - BIG(c1 * s)
module.vec_znx_big_normalize(log_base2k, &mut ct, &buf_big, &mut carry);
ct.print(ct.sl());
// (c0 + e, c1)
module.add_normal(
log_base2k,
&mut ct,
0, // c0
log_base2k * ct_size,
&mut source,
3.2,
19.0,
);
// Decrypt
// DFT(c1 * s)
module.svp_apply_dft(&mut buf_dft, &s_ppol, &ct, 1);
// BIG(c1 * s) = IDFT(DFT(c1 * s))
module.vec_znx_idft_tmp_a(&mut buf_big, &mut buf_dft);
// BIG(c1 * s) + c0
module.vec_znx_big_add_small_inplace(&mut buf_big, &ct);
// m + e <- BIG(c1 * s + c0)
let mut res: VecZnx = module.new_vec_znx(1, ct_size);
module.vec_znx_big_normalize(log_base2k, &mut res, &buf_big, &mut carry);
// have = m * 2^{log_scale} + e
let mut have: Vec<i64> = vec![i64::default(); n];
res.decode_vec_i64(0, log_base2k, res.size() * log_base2k, &mut have);
let scale: f64 = (1 << (res.size() * log_base2k - log_scale)) as f64;
izip!(want.iter(), have.iter())
.enumerate()
.for_each(|(i, (a, b))| {
println!("{}: {} {}", i, a, (*b as f64) / scale);
})
}