Struct DefaultModswitchStrategy

pub struct DefaultModswitchStrategy<Params: BGVCiphertextParams, N: BGVNoiseEstimator<Params>, const LOG: bool> { /* private fields */ }

Default modulus-switch strategy for BGV, which performs a certain number of modulus-switches before each multiplication.

The general strategy is as follows:

• only mod-switch before multiplications
• never introduce new RNS factors, only remove current ones
• use the provided BGVNoiseEstimator to determine when and by how much we should reduce the ciphertext modulus

These points lead to a relatively simple and generally well-performing modulus switching strategy. However, there may be situations where deviating from 1. could lead to a lower number of mod-switches (and thus better performance), and deviating from 2. could be used for a finer-tuned mod-switching, and thus less noise growth.

Implementations

impl<Params: BGVCiphertextParams> DefaultModswitchStrategy<Params, AlwaysZeroNoiseEstimator, false>

pub fn never_modswitch() -> Self

Create a DefaultModswitchStrategy that never performs modulus switching, except when necessary because operands are defined modulo different RNS bases.

Using this is not recommended, except for linear circuits, or circuits with very low multiplicative depth.

impl<Params: BGVCiphertextParams, N: BGVNoiseEstimator<Params>, const LOG: bool> DefaultModswitchStrategy<Params, N, LOG>

pub fn new(noise_estimator: N) -> Self

pub fn from_noise_level( &self, noise_level: N::CriticalQuantityLevel, ) -> <Self as BGVModswitchStrategy<Params>>::CiphertextInfo

Trait Implementations

impl<Params: BGVCiphertextParams, N: BGVNoiseEstimator<Params>, const LOG: bool> BGVModswitchStrategy<Params> for DefaultModswitchStrategy<Params, N, LOG>

type CiphertextInfo = <N as BGVNoiseEstimator<Params>>::CriticalQuantityLevel

Additional information that is associated to a ciphertext and is used to determine when and how to modulus-switch. This will most likely be some form of estimate of the noise in the ciphertext.

fn evaluate_circuit<R>( &self, circuit: &PlaintextCircuit<R::Type>, ring: R, P: &PlaintextRing<Params>, C_master: &CiphertextRing<Params>, inputs: &[ModulusAwareCiphertext<Params, Self>], rk: Option<&RelinKey<'_, Params>>, gks: &[(CyclotomicGaloisGroupEl, KeySwitchKey<'_, Params>)], key_switches: &mut usize, debug_sk: Option<&SecretKey<Params>>, ) -> Vec<ModulusAwareCiphertext<Params, Self>>

where R: RingStore, R::Type: AsBGVPlaintext<Params>,

Evaluates the given circuit homomorphically on the given encrypted inputs. This includes performing modulus-switches at suitable times.

fn info_for_fresh_encryption( &self, P: &PlaintextRing<Params>, C: &CiphertextRing<Params>, hwt: Option<usize>, ) -> <Self as BGVModswitchStrategy<Params>>::CiphertextInfo

fn clone_info(&self, info: &Self::CiphertextInfo) -> Self::CiphertextInfo

fn print_info( &self, P: &PlaintextRing<Params>, C_master: &CiphertextRing<Params>, ct: &ModulusAwareCiphertext<Params, Self>, )

fn clone_ct( &self, P: &PlaintextRing<Params>, C_master: &CiphertextRing<Params>, ct: &ModulusAwareCiphertext<Params, Self>, ) -> ModulusAwareCiphertext<Params, Self>