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Improve noise formulas in multi-bit CJP verification #1223

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24 changes: 10 additions & 14 deletions compilers/concrete-optimizer/brute-force-optimizer/src/multi_bit_cjp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,11 +50,12 @@ impl Problem for MultiBitCJPConstraint {
type Param = MultiBitCJPParams;

fn verify(&self, param: Self::Param) -> bool {
// TODO CHANGE NOISE FORMULAE
let poly_size = 1 << param.log_poly_size;

// Calculate minimal variance for LWE key switching
let variance_ksk = minimal_variance_lwe(param.small_lwe_dim, 64, self.security_level);

// Calculate key switching variance with updated parameters
let v_ks = variance_keyswitch(
param.big_lwe_dim(),
param.base_log_ks,
Expand All @@ -63,17 +64,10 @@ impl Problem for MultiBitCJPConstraint {
variance_ksk,
);

let variance_bsk =
minimal_variance_glwe(param.glwe_dim, poly_size, 64, self.security_level);
// let v_pbs = variance_blind_rotate(
// param.small_lwe_dim,
// param.glwe_dim,
// poly_size,
// param.base_log_pbs,
// param.level_pbs,
// 64,
// variance_bsk,
// );
// Calculate minimal variance for GLWE bootstrapping
let variance_bsk = minimal_variance_glwe(param.glwe_dim, poly_size, 64, self.security_level);

// Calculate multi-bit blind rotation variance with all parameters
let v_pbs = variance_multi_bit_blind_rotate(
param.small_lwe_dim,
param.glwe_dim,
Expand All @@ -86,13 +80,15 @@ impl Problem for MultiBitCJPConstraint {
self.grouping_factor,
self.jit_fft,
);

// Calculate modulus switching noise with binary key
let v_ms = estimate_modulus_switching_noise_with_binary_key(
param.small_lwe_dim,
param.log_poly_size,
64,
);
// println!("v_pbs: {}", v_pbs);
// println!("v_ks: {}", v_ks);

// Verify total noise is within constraint
v_pbs * (1 << (2 * self.log_norm2)) as f64 + v_ks + v_ms < self.variance_constraint
}

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