Struct SparseKeyEncapsulationKey 

pub struct SparseKeyEncapsulationKey<Inst: BFVInstantiation> {
    pub C_sparse_sk: CiphertextRing<Inst>,
    pub switch_to_sparse_key: KeySwitchKey<Inst>,
    pub encapsulated_key: Ciphertext<Inst>,
}

Data required for performing thin bootstrapping with sparse key encapsulation.

Sparse key encapsulation refers to key-switching a ciphertext to a sparse secret key just before homomorphic decryption (which happens at a very low ciphertext modulus, which can offset the security loss due to key sparsity), and thus introduce much less noise that has to be homomorphically removed.

Fields

C_sparse_sk: CiphertextRing<Inst>

Ciphertext ring with small modulus, over which encryptions with the sparse key remain secure.

switch_to_sparse_key: KeySwitchKey<Inst>

Key-switch key to switch a ciphertext encrypted by the standard key to a ciphertext encrypted by the sparse key.

This is defined w.r.t. the switch-to-sparse ciphertext ring, which has a significantly smaller modulus than the standard ciphertext ring. This is necessary for security.

encapsulated_key: Ciphertext<Inst>

An encryption of the sparse secret key (mapped into the plaintext ring by taking a shortest lift to R) w.r.t. the standard secret key.

Implementations

impl<Params> SparseKeyEncapsulationKey<Params>

where Params: BFVInstantiation,

pub fn create<R: CryptoRng + Rng>( P: &PlaintextRing<Params>, C: &CiphertextRing<Params>, C_sparse_sk: CiphertextRing<Params>, sparse_sk: SecretKey<Params>, standard_sk: &SecretKey<Params>, rng: R, noise_sigma: f64, ) -> Self

pub fn new<R: CryptoRng + Rng>( P: &PlaintextRing<Params>, C: &CiphertextRing<Params>, standard_sk: &SecretKey<Params>, C_sparse_rns_factor_count: usize, hwt: usize, rng: R, noise_sigma: f64, ) -> Self