poulpy/core/src/lwe/keyswtich.rs

use backend::{Backend, FFT64, Module, Scratch, VecZnxOps, ZnxView, ZnxViewMut, ZnxZero};
use sampling::source::Source;

use crate::{FourierGLWESecret, GLWECiphertext, GLWESecret, GLWESwitchingKey, Infos, LWECiphertext, LWESecret, ScratchCore};

/// A special [GLWESwitchingKey] required to for the conversion from [GLWECiphertext] to [LWECiphertext].
pub struct GLWEToLWESwitchingKey<D, B: Backend>(GLWESwitchingKey<D, B>);

impl GLWEToLWESwitchingKey<Vec<u8>, FFT64> {
    pub fn alloc(module: &Module<FFT64>, basek: usize, k: usize, rows: usize, rank: usize) -> Self {
        Self(GLWESwitchingKey::alloc(module, basek, k, rows, 1, rank, 1))
    }

    pub fn encrypt_sk_scratch_space(module: &Module<FFT64>, basek: usize, k: usize, rank: usize) -> usize {
        FourierGLWESecret::bytes_of(module, rank)
            + (GLWESwitchingKey::encrypt_sk_scratch_space(module, basek, k, rank, rank) | GLWESecret::bytes_of(module, rank))
    }
}

impl<D: AsMut<[u8]> + AsRef<[u8]>> GLWEToLWESwitchingKey<D, FFT64> {
    pub fn encrypt_sk<DLwe, DGlwe>(
        &mut self,
        module: &Module<FFT64>,
        sk_lwe: &LWESecret<DLwe>,
        sk_glwe: &GLWESecret<DGlwe>,
        source_xa: &mut Source,
        source_xe: &mut Source,
        sigma: f64,
        scratch: &mut Scratch,
    ) where
        DLwe: AsRef<[u8]>,
        DGlwe: AsRef<[u8]>,
    {
        #[cfg(debug_assertions)]
        {
            assert!(sk_lwe.n() <= module.n());
        }

        let (mut sk_lwe_as_glwe_dft, scratch1) = scratch.tmp_fourier_glwe_secret(module, 1);

        {
            let (mut sk_lwe_as_glwe, _) = scratch1.tmp_glwe_secret(module, 1);
            sk_lwe_as_glwe.data.zero();
            sk_lwe_as_glwe.data.at_mut(0, 0)[..sk_lwe.n()].copy_from_slice(sk_lwe.data.at(0, 0));
            module.vec_znx_automorphism_inplace(-1, &mut sk_lwe_as_glwe.data, 0);
            sk_lwe_as_glwe_dft.set(module, &sk_lwe_as_glwe);
        }

        self.0.encrypt_sk(
            module,
            sk_glwe,
            &sk_lwe_as_glwe_dft,
            source_xa,
            source_xe,
            sigma,
            scratch1,
        );
    }
}

/// A special [GLWESwitchingKey] required to for the conversion from [LWECiphertext] to [GLWECiphertext].
pub struct LWEToGLWESwitchingKey<D, B: Backend>(GLWESwitchingKey<D, B>);

impl LWEToGLWESwitchingKey<Vec<u8>, FFT64> {
    pub fn alloc(module: &Module<FFT64>, basek: usize, k: usize, rows: usize, rank: usize) -> Self {
        Self(GLWESwitchingKey::alloc(module, basek, k, rows, 1, 1, rank))
    }

    pub fn encrypt_sk_scratch_space(module: &Module<FFT64>, basek: usize, k: usize, rank: usize) -> usize {
        GLWESwitchingKey::encrypt_sk_scratch_space(module, basek, k, 1, rank) + GLWESecret::bytes_of(module, 1)
    }
}

impl<D: AsMut<[u8]> + AsRef<[u8]>> LWEToGLWESwitchingKey<D, FFT64> {
    pub fn encrypt_sk<DLwe, DGlwe>(
        &mut self,
        module: &Module<FFT64>,
        sk_lwe: &LWESecret<DLwe>,
        sk_glwe: &FourierGLWESecret<DGlwe, FFT64>,
        source_xa: &mut Source,
        source_xe: &mut Source,
        sigma: f64,
        scratch: &mut Scratch,
    ) where
        DLwe: AsRef<[u8]>,
        DGlwe: AsRef<[u8]>,
    {
        #[cfg(debug_assertions)]
        {
            assert!(sk_lwe.n() <= module.n());
        }

        let (mut sk_lwe_as_glwe, scratch1) = scratch.tmp_glwe_secret(module, 1);
        sk_lwe_as_glwe.data.at_mut(0, 0)[..sk_lwe.n()].copy_from_slice(sk_lwe.data.at(0, 0));
        sk_lwe_as_glwe.data.at_mut(0, 0)[sk_lwe.n()..].fill(0);
        module.vec_znx_automorphism_inplace(-1, &mut sk_lwe_as_glwe.data, 0);

        self.0.encrypt_sk(
            module,
            &sk_lwe_as_glwe,
            &sk_glwe,
            source_xa,
            source_xe,
            sigma,
            scratch1,
        );
    }
}

pub struct LWESwitchingKey<D, B: Backend>(GLWESwitchingKey<D, B>);

impl LWESwitchingKey<Vec<u8>, FFT64> {
    pub fn alloc(module: &Module<FFT64>, basek: usize, k: usize, rows: usize) -> Self {
        Self(GLWESwitchingKey::alloc(module, basek, k, rows, 1, 1, 1))
    }

    pub fn encrypt_sk_scratch_space(module: &Module<FFT64>, basek: usize, k: usize) -> usize {
        GLWESecret::bytes_of(module, 1)
            + FourierGLWESecret::bytes_of(module, 1)
            + GLWESwitchingKey::encrypt_sk_scratch_space(module, basek, k, 1, 1)
    }
}

impl<D: AsMut<[u8]> + AsRef<[u8]>> LWESwitchingKey<D, FFT64> {
    pub fn encrypt_sk<DIn, DOut>(
        &mut self,
        module: &Module<FFT64>,
        sk_lwe_in: &LWESecret<DIn>,
        sk_lwe_out: &LWESecret<DOut>,
        source_xa: &mut Source,
        source_xe: &mut Source,
        sigma: f64,
        scratch: &mut Scratch,
    ) where
        DIn: AsRef<[u8]>,
        DOut: AsRef<[u8]>,
    {
        #[cfg(debug_assertions)]
        {
            assert!(sk_lwe_in.n() <= module.n());
            assert!(sk_lwe_out.n() <= module.n());
        }

        let (mut sk_in_glwe, scratch1) = scratch.tmp_glwe_secret(module, 1);
        let (mut sk_out_glwe, scratch2) = scratch1.tmp_fourier_glwe_secret(module, 1);

        sk_in_glwe.data.at_mut(0, 0)[..sk_lwe_out.n()].copy_from_slice(sk_lwe_out.data.at(0, 0));
        sk_in_glwe.data.at_mut(0, 0)[sk_lwe_out.n()..].fill(0);
        module.vec_znx_automorphism_inplace(-1, &mut sk_in_glwe.data, 0);
        sk_out_glwe.set(module, &sk_in_glwe);
        sk_in_glwe.data.at_mut(0, 0)[..sk_lwe_in.n()].copy_from_slice(sk_lwe_in.data.at(0, 0));
        sk_in_glwe.data.at_mut(0, 0)[sk_lwe_in.n()..].fill(0);
        module.vec_znx_automorphism_inplace(-1, &mut sk_in_glwe.data, 0);

        self.0.encrypt_sk(
            module,
            &sk_in_glwe,
            &sk_out_glwe,
            source_xa,
            source_xe,
            sigma,
            scratch2,
        );
    }
}

impl LWECiphertext<Vec<u8>> {
    pub fn from_glwe_scratch_space(
        module: &Module<FFT64>,
        basek: usize,
        k_lwe: usize,
        k_glwe: usize,
        k_ksk: usize,
        rank: usize,
    ) -> usize {
        GLWECiphertext::bytes_of(module, basek, k_lwe, 1)
            + GLWECiphertext::keyswitch_scratch_space(module, basek, k_lwe, k_glwe, k_ksk, 1, rank, 1)
    }

    pub fn keyswitch_scratch_space(
        module: &Module<FFT64>,
        basek: usize,
        k_lwe_out: usize,
        k_lwe_in: usize,
        k_ksk: usize,
    ) -> usize {
        GLWECiphertext::bytes_of(module, basek, k_lwe_out.max(k_lwe_in), 1)
            + GLWECiphertext::keyswitch_inplace_scratch_space(module, basek, k_lwe_out, k_ksk, 1, 1)
    }
}

impl<DLwe: AsRef<[u8]> + AsMut<[u8]>> LWECiphertext<DLwe> {
    pub fn sample_extract<DGlwe>(&mut self, a: &GLWECiphertext<DGlwe>)
    where
        DGlwe: AsRef<[u8]>,
    {
        #[cfg(debug_assertions)]
        {
            assert!(self.n() <= a.n());
        }

        let min_size: usize = self.size().min(a.size());
        let n: usize = self.n();

        self.data.zero();
        (0..min_size).for_each(|i| {
            let data_lwe: &mut [i64] = self.data.at_mut(0, i);
            data_lwe[0] = a.data.at(0, i)[0];
            data_lwe[1..].copy_from_slice(&a.data.at(1, i)[..n]);
        });
    }

    pub fn from_glwe<DGlwe, DKs>(
        &mut self,
        module: &Module<FFT64>,
        a: &GLWECiphertext<DGlwe>,
        ks: &GLWEToLWESwitchingKey<DKs, FFT64>,
        scratch: &mut Scratch,
    ) where
        DGlwe: AsRef<[u8]>,
        DKs: AsRef<[u8]>,
    {
        #[cfg(debug_assertions)]
        {
            assert_eq!(self.basek(), a.basek());
        }
        let (mut tmp_glwe, scratch1) = scratch.tmp_glwe_ct(module, a.basek(), self.k(), 1);
        tmp_glwe.keyswitch(module, a, &ks.0, scratch1);
        self.sample_extract(&tmp_glwe);
    }

    pub fn keyswitch<A, DKs>(
        &mut self,
        module: &Module<FFT64>,
        a: &LWECiphertext<A>,
        ksk: &LWESwitchingKey<DKs, FFT64>,
        scratch: &mut Scratch,
    ) where
        A: AsRef<[u8]>,
        DKs: AsRef<[u8]>,
    {
        #[cfg(debug_assertions)]
        {
            assert!(self.n() <= module.n());
            assert!(a.n() <= module.n());
            assert_eq!(self.basek(), a.basek());
        }

        let max_k: usize = self.k().max(a.k());
        let basek: usize = self.basek();

        let (mut glwe, scratch1) = scratch.tmp_glwe_ct(&module, basek, max_k, 1);
        glwe.data.zero();

        let n_lwe: usize = a.n();

        (0..a.size()).for_each(|i| {
            let data_lwe: &[i64] = a.data.at(0, i);
            glwe.data.at_mut(0, i)[0] = data_lwe[0];
            glwe.data.at_mut(1, i)[..n_lwe].copy_from_slice(&data_lwe[1..]);
        });

        glwe.keyswitch_inplace(module, &ksk.0, scratch1);

        self.sample_extract(&glwe);
    }
}

impl GLWECiphertext<Vec<u8>> {
    pub fn from_lwe_scratch_space(
        module: &Module<FFT64>,
        basek: usize,
        k_lwe: usize,
        k_glwe: usize,
        k_ksk: usize,
        rank: usize,
    ) -> usize {
        GLWECiphertext::keyswitch_scratch_space(module, basek, k_glwe, k_lwe, k_ksk, 1, 1, rank)
            + GLWECiphertext::bytes_of(module, basek, k_lwe, 1)
    }
}

impl<D: AsRef<[u8]> + AsMut<[u8]>> GLWECiphertext<D> {
    pub fn from_lwe<DLwe, DKsk>(
        &mut self,
        module: &Module<FFT64>,
        lwe: &LWECiphertext<DLwe>,
        ksk: &LWEToGLWESwitchingKey<DKsk, FFT64>,
        scratch: &mut Scratch,
    ) where
        DLwe: AsRef<[u8]>,
        DKsk: AsRef<[u8]>,
    {
        #[cfg(debug_assertions)]
        {
            assert!(lwe.n() <= self.n());
            assert_eq!(self.basek(), self.basek());
        }

        let (mut glwe, scratch1) = scratch.tmp_glwe_ct(module, lwe.basek(), lwe.k(), 1);
        glwe.data.zero();

        let n_lwe: usize = lwe.n();

        (0..lwe.size()).for_each(|i| {
            let data_lwe: &[i64] = lwe.data.at(0, i);
            glwe.data.at_mut(0, i)[0] = data_lwe[0];
            glwe.data.at_mut(1, i)[..n_lwe].copy_from_slice(&data_lwe[1..]);
        });

        self.keyswitch(module, &glwe, &ksk.0, scratch1);
    }
}