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use crate::{
core::{
actually_used_field::ActuallyUsedField,
circuits::boolean::{
boolean_value::BooleanValue,
utils::{
abs,
equal,
euclidean_division,
greater_than,
is_number_zero,
keep_ls_bits,
shift_right,
subtraction_circuit,
CircuitType,
},
},
compile_passes::{compilation_pass::LocalCompilationPass, new_eda_bit},
expressions::{
conversion_expr::ConversionExpr,
expr::Expr,
field_expr::FieldExpr,
other_expr::OtherExpr,
},
global_value::{
curve_value::CurveValue,
global_expr_store::with_local_expr_store_as_global,
value::FieldValue,
},
ir_builder::IRBuilder,
},
traits::{GetBit, Reveal},
utils::{elliptic_curve::ProjectiveEdwardsPoint, field::BaseField, number::Number},
STATISTICAL_SECURITY_FACTOR,
};
use ff::Field;
use rustc_hash::FxHashMap;
/// Information about an argument.
#[derive(Debug, Clone, Copy, Default)]
struct ArgInfo {
will_have_unsigned_binary_decomposition: bool,
will_have_signed_binary_decomposition: bool,
}
impl ArgInfo {
fn make_from_extra<F: ActuallyUsedField>(expr_id: usize, expr_store: &IRBuilder) -> Self {
let mut res = Self::default();
if expr_store.get_is_plaintext(expr_id) {
res.will_have_unsigned_binary_decomposition = true;
res.will_have_signed_binary_decomposition = true;
} else if let Some(ConversionExpr::BitToBitNum(v, signed)) =
F::expr_to_conversion_expr(expr_store.get_expr(expr_id).clone())
{
if signed {
res.will_have_signed_binary_decomposition = true;
} else {
res.will_have_unsigned_binary_decomposition = true;
// A unsigned binary decomposition of a positive number is a signed one too.
if v.len() < F::CAPACITY as usize {
res.will_have_signed_binary_decomposition = true;
}
}
}
res
}
fn find_common_signedness(&self, other: &Self) -> Option<bool> {
if self.will_have_signed_binary_decomposition && other.will_have_signed_binary_decomposition
{
Some(true)
} else if self.will_have_unsigned_binary_decomposition
&& other.will_have_unsigned_binary_decomposition
{
Some(false)
} else {
None
}
}
}
/// Information about Eq.
#[derive(Debug, Clone, Copy, Default)]
struct EqInfo {
is_result_plaintext: bool,
/// Information about the left argument.
left_info: ArgInfo,
/// Information about the right argument.
right_info: ArgInfo,
}
/// Builds unoptimized boolean circuits.
#[derive(Default)]
pub struct BooleanCircuitBuilder {
expr_store: IRBuilder,
projective_cache: FxHashMap<usize, [usize; 3]>,
}
impl BooleanCircuitBuilder {
fn build_circuits<F: ActuallyUsedField>(
&mut self,
expr: FieldExpr<F, usize>,
is_plaintext: bool,
) -> Expr<usize> {
let expr_store = &mut self.expr_store;
use FieldExpr::*;
match expr {
Equal(e1, e2)
if !expr_store.get_is_plaintext(e1) || !expr_store.get_is_plaintext(e2) =>
{
let left_info = ArgInfo::make_from_extra::<F>(e1, expr_store);
let right_info = ArgInfo::make_from_extra::<F>(e2, expr_store);
let eq_info = EqInfo {
is_result_plaintext: is_plaintext,
left_info,
right_info,
};
with_local_expr_store_as_global(
|| {
let left = FieldValue::<F>::from_id(e1);
let right = FieldValue::<F>::from_id(e2);
if eq_info.is_result_plaintext {
// Here we will end up using
// the gate that outputs the result in plaintext.
FieldValue::new(Equal(right - left, 0.into()))
} else {
FieldValue::<F>::from(
if let Some(signedness) = eq_info
.left_info
.find_common_signedness(&eq_info.right_info)
{
// If both left and right already have or will have
// a boolean decomposition of the same sign,
// we use the boolean circuit.
equal(left, right, signedness, CircuitType::default())
} else {
// Otherwise we use the eda-bit.
is_number_zero(right - left, CircuitType::default())
},
)
}
.expr()
},
expr_store,
)
}
Gt(e1, e2, signed)
if !expr_store.get_is_plaintext(e1) || !expr_store.get_is_plaintext(e2) =>
{
let left_info = ArgInfo::make_from_extra::<F>(e1, expr_store);
let right_info = ArgInfo::make_from_extra::<F>(e2, expr_store);
with_local_expr_store_as_global(
|| {
let left = FieldValue::<F>::from_id(e1);
let right = FieldValue::<F>::from_id(e2);
let (l_min, l_max) = left.bounds().min_and_max(signed);
let (r_min, r_max) = right.bounds().min_and_max(signed);
FieldValue::<F>::from(
if left_info.find_common_signedness(&right_info).is_some()
|| r_min.does_add_signed_overflow(-l_max)
|| r_max.does_add_signed_overflow(-l_min)
|| !signed
&& (l_min.is_ge_zero() || r_min.is_ge_zero())
&& (l_max.is_lt_zero() || r_max.is_lt_zero())
{
let signed_input = left_info
.find_common_signedness(&right_info)
.unwrap_or(signed);
// If both left and right already have or will have a boolean
// decomposition, we use the boolean circuit.
greater_than(
left,
right,
BooleanValue::from(false),
signed,
signed_input,
)
} else {
// get_bit internally optimizes the depth - it might be less than
// log2(F::NUM_BITS)
(right - left).get_bit(F::NUM_BITS as usize - 1, true)
},
)
.expr()
},
expr_store,
)
}
Ge(e1, e2, signed)
if !expr_store.get_is_plaintext(e1) || !expr_store.get_is_plaintext(e2) =>
{
let left_info = ArgInfo::make_from_extra::<F>(e1, expr_store);
let right_info = ArgInfo::make_from_extra::<F>(e2, expr_store);
with_local_expr_store_as_global(
|| {
let left = FieldValue::<F>::from_id(e1);
let right = FieldValue::<F>::from_id(e2);
let (l_min, l_max) = left.bounds().min_and_max(signed);
let (r_min, r_max) = right.bounds().min_and_max(signed);
FieldValue::<F>::from(
if left_info.find_common_signedness(&right_info).is_some()
|| l_min.does_add_signed_overflow(-r_max)
|| l_max.does_add_signed_overflow(-r_min)
|| !signed
&& (l_min.is_ge_zero() || r_min.is_ge_zero())
&& (l_max.is_lt_zero() || r_max.is_lt_zero())
{
let signed_input = left_info
.find_common_signedness(&right_info)
.unwrap_or(signed);
// If both left and right already have or will have a boolean
// decomposition, we use the boolean circuit.
greater_than(
left,
right,
BooleanValue::from(true),
signed,
signed_input,
)
} else {
// get_bit internally optimizes the depth - it might be less than
// log2(F::NUM_BITS)
!(left - right).get_bit(F::NUM_BITS as usize - 1, true)
},
)
.expr()
},
expr_store,
)
}
Abs(e) => with_local_expr_store_as_global(
|| abs(FieldValue::<F>::from_id(e)).expr(),
expr_store,
),
Div(e1, e2) if !expr_store.get_is_plaintext(e1) || !expr_store.get_is_plaintext(e2) => {
with_local_expr_store_as_global(
|| {
euclidean_division(
FieldValue::<F>::from_id(e1),
FieldValue::<F>::from_id(e2),
)
.0
.expr()
},
expr_store,
)
}
Rem(e1, e2) if !expr_store.get_is_plaintext(e1) || !expr_store.get_is_plaintext(e2) => {
with_local_expr_store_as_global(
|| {
euclidean_division(
FieldValue::<F>::from_id(e1),
FieldValue::<F>::from_id(e2),
)
.1
.expr()
},
expr_store,
)
}
LogicalRightShift(e, c) => with_local_expr_store_as_global(
|| shift_right(FieldValue::<F>::from_id(e), c, false).expr(),
expr_store,
),
KeepLsBits(e, c, signed_output) => with_local_expr_store_as_global(
|| keep_ls_bits(FieldValue::<F>::from_id(e), c, signed_output).expr(),
expr_store,
),
Cap(e, size) => {
let eda_bit_size = (size + STATISTICAL_SECURITY_FACTOR).min(F::NUM_BITS as usize);
let res_bits = if !expr_store.get_is_plaintext(e)
&& Number::power_of_two(size) + Number::power_of_two(eda_bit_size)
< F::modulus()
{
with_local_expr_store_as_global(
|| {
let e = FieldValue::<F>::from_id(e);
let (eda_bit_scalar, eda_bit_bits, _, _, _) =
new_eda_bit::<F>(eda_bit_size, false);
let sum = e + eda_bit_scalar;
let revealed_sum = sum.reveal();
let revealed_sum_bits = (0..size)
.map(|i| revealed_sum.get_bit(i, false))
.collect::<Vec<BooleanValue>>();
subtraction_circuit(
revealed_sum_bits,
eda_bit_bits
.into_iter()
.take(size)
// if the result is plaintext, we can reveal these bits, but not
// the statistical masking
// ones.
.map(|b| if is_plaintext { b.reveal() } else { b })
.collect::<Vec<BooleanValue>>(),
CircuitType::default(),
)
.into_iter()
.map(|bit| bit.get_id())
.collect::<Vec<usize>>()
},
&mut self.expr_store,
)
} else {
(0..size)
.map(|i| {
self.expr_store.new_expr(F::conversion_expr_to_expr(
ConversionExpr::BitNumToBit(e, i, false),
))
})
.collect()
};
F::conversion_expr_to_expr(ConversionExpr::<F, _>::BitToBitNum(res_bits, false))
}
_ => F::field_expr_to_expr(expr),
}
}
fn build_other_expr(&mut self, expr: OtherExpr<usize>) -> Expr<usize> {
match expr {
OtherExpr::ToProjective(c, idx) => {
let cache_value = self.projective_cache.entry(c).or_insert_with(|| {
with_local_expr_store_as_global(
|| {
let c = CurveValue::new(c);
let arr = if c.is_plaintext() {
let (x, y, z, _) = c.to_extended_public();
[x, y, z]
} else {
let (da_point_curve, da_point_proj) = CurveValue::da_point();
let masked = (c - da_point_curve).reveal();
let (x, y, z, _) = masked.to_extended_public();
let masked_proj =
ProjectiveEdwardsPoint::new((x, y, z), true, true);
let res = masked_proj + da_point_proj;
[res.X, res.Y, res.Z]
};
arr.map(|x| x.get_id())
},
&mut self.expr_store,
)
});
cache_value
.get(idx)
.cloned()
.map(|expr_id| self.expr_store.get_expr(expr_id).clone())
.unwrap_or(Expr::Base(FieldExpr::Val(BaseField::ZERO)))
}
_ => Expr::Other(expr),
}
}
}
impl LocalCompilationPass for BooleanCircuitBuilder {
fn expr_store(&mut self) -> &mut IRBuilder {
&mut self.expr_store
}
fn transform(&mut self, expr: Expr<usize>, is_plaintext: bool) -> Expr<usize> {
match expr {
Expr::Scalar(e) => self.build_circuits(e, is_plaintext),
Expr::Base(e) => self.build_circuits(e, is_plaintext),
Expr::Other(e) => self.build_other_expr(e),
_ => expr,
}
}
}