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refactor(levm): remove redundant parse of coordinates (#1731)
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**Motivation**

<!-- Why does this pull request exist? What are its goals? -->
In this PR we refactor the parsing of the G1/G2 points to make it
simpler.

**Description**

<!-- A clear and concise general description of the changes this PR
introduces -->
The function `parse_g1_point` and `parse_g2_point` get a slice of the
bytes instead of the coordinates. Inside the function, the parse of the
coordinates are made.
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@tomip01
tomip01 authored Jan 16, 2025
1 parent 0f2a7ee commit 393fc3f
Showing 1 changed file with 37 additions and 63 deletions.
100 changes: 37 additions & 63 deletions crates/vm/levm/src/precompiles.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1181,7 +1181,7 @@ pub fn bls12_g1add(
gas_for_call: u64,
consumed_gas: &mut u64,
) -> Result<Bytes, VMError> {
// Two inputs of 128 bytes are requiered
// Two inputs of 128 bytes are required
if calldata.len() != BLS12_381_G1ADD_VALID_INPUT_LENGTH {
return Err(VMError::PrecompileError(PrecompileError::ParsingInputError));
}
Expand All @@ -1190,15 +1190,8 @@ pub fn bls12_g1add(
increase_precompile_consumed_gas(gas_for_call, BLS12_381_G1ADD_COST, consumed_gas)
.map_err(|_| VMError::PrecompileError(PrecompileError::NotEnoughGas))?;

// Each coordinate is 64 bytes
let first_point_x = parse_coordinate(calldata.get(0..64))?;
let first_point_y = parse_coordinate(calldata.get(64..128))?;
let second_point_x = parse_coordinate(calldata.get(128..192))?;
let second_point_y = parse_coordinate(calldata.get(192..256))?;

let first_g1_point = parse_g1_point(first_point_x, first_point_y, true)?;

let second_g1_point = parse_g1_point(second_point_x, second_point_y, true)?;
let first_g1_point = parse_g1_point(calldata.get(0..128), true)?;
let second_g1_point = parse_g1_point(calldata.get(128..256), true)?;

let result_of_addition = G1Affine::from(first_g1_point.add(&second_g1_point));

Expand Down Expand Up @@ -1234,26 +1227,20 @@ pub fn bls12_g1msm(
// s_i are scalars (numbers)
// P_i are points in the group (in this case, points in G1)
for i in 0..k {
let x_offset = i
let point_offset = i
.checked_mul(BLS12_381_G1_MSM_PAIR_LENGTH)
.ok_or(InternalError::ArithmeticOperationOverflow)?;
let y_offset = x_offset
.checked_add(64)
.ok_or(InternalError::ArithmeticOperationOverflow)?;
let scalar_offset = y_offset
.checked_add(64)
let scalar_offset = point_offset
.checked_add(128)
.ok_or(InternalError::ArithmeticOperationOverflow)?;
let pair_end = scalar_offset
.checked_add(32)
.ok_or(InternalError::ArithmeticOperationOverflow)?;

let x = parse_coordinate(calldata.get(x_offset..y_offset))?;
let y = parse_coordinate(calldata.get(y_offset..scalar_offset))?;
let g1 = parse_g1_point(x, y, false)?;

let point = parse_g1_point(calldata.get(point_offset..scalar_offset), false)?;
let scalar = parse_scalar(calldata.get(scalar_offset..pair_end))?;

let scaled_point = G1Projective::mul(g1, scalar);
let scaled_point = G1Projective::mul(point, scalar);
result = result.add(&scaled_point);
}
let mut output = [0u8; 128];
Expand Down Expand Up @@ -1284,19 +1271,8 @@ pub fn bls12_g2add(
increase_precompile_consumed_gas(gas_for_call, BLS12_381_G2ADD_COST, consumed_gas)
.map_err(|_| VMError::PrecompileError(PrecompileError::NotEnoughGas))?;

// Each coordinate is 64 bytes
// There are 4 coordinates per G2 point
let first_x_1 = parse_coordinate(calldata.get(0..64))?;
let first_x_2 = parse_coordinate(calldata.get(64..128))?;
let first_y_1 = parse_coordinate(calldata.get(128..192))?;
let first_y_2 = parse_coordinate(calldata.get(192..256))?;
let second_x_1 = parse_coordinate(calldata.get(256..320))?;
let second_x_2 = parse_coordinate(calldata.get(320..384))?;
let second_y_1 = parse_coordinate(calldata.get(384..448))?;
let second_y_2 = parse_coordinate(calldata.get(448..512))?;

let first_g2_point = parse_g2_point(first_x_1, first_x_2, first_y_1, first_y_2, true)?;
let second_g2_point = parse_g2_point(second_x_1, second_x_2, second_y_1, second_y_2, true)?;
let first_g2_point = parse_g2_point(calldata.get(0..256), true)?;
let second_g2_point = parse_g2_point(calldata.get(256..512), true)?;

let result_of_addition = G2Affine::from(first_g2_point.add(&second_g2_point));

Expand All @@ -1307,7 +1283,7 @@ pub fn bls12_g2add(
};

let mut padded_result = Vec::new();
// The crate bls12_381 deserialize the G2 point as x_2 || x_1 || y_2 || y_1
// The crate bls12_381 deserialize the G2 point as x_1 || x_0 || y_1 || y_0
// https://docs.rs/bls12_381/0.8.0/src/bls12_381/g2.rs.html#284-299
add_padded_coordinate(&mut padded_result, result_bytes.get(48..96))?;
add_padded_coordinate(&mut padded_result, result_bytes.get(0..48))?;
Expand All @@ -1332,31 +1308,17 @@ pub fn bls12_g2msm(

let mut result = G2Projective::identity();
for i in 0..k {
let x_0_offset = i
let point_offset = i
.checked_mul(BLS12_381_G2_MSM_PAIR_LENGTH)
.ok_or(InternalError::ArithmeticOperationOverflow)?;
let x_1_offset = x_0_offset
.checked_add(64)
.ok_or(InternalError::ArithmeticOperationOverflow)?;
let y_0_offset = x_1_offset
.checked_add(64)
.ok_or(InternalError::ArithmeticOperationOverflow)?;
let y_1_offset = y_0_offset
.checked_add(64)
.ok_or(InternalError::ArithmeticOperationOverflow)?;
let scalar_offset = y_1_offset
.checked_add(64)
let scalar_offset = point_offset
.checked_add(256)
.ok_or(InternalError::ArithmeticOperationOverflow)?;
let pair_end = scalar_offset
.checked_add(32)
.ok_or(InternalError::ArithmeticOperationOverflow)?;

let x_0 = parse_coordinate(calldata.get(x_0_offset..x_1_offset))?;
let x_1 = parse_coordinate(calldata.get(x_1_offset..y_0_offset))?;
let y_0 = parse_coordinate(calldata.get(y_0_offset..y_1_offset))?;
let y_1 = parse_coordinate(calldata.get(y_1_offset..scalar_offset))?;
let point = parse_g2_point(x_0, x_1, y_0, y_1, false)?;

let point = parse_g2_point(calldata.get(point_offset..scalar_offset), false)?;
let scalar = parse_scalar(calldata.get(scalar_offset..pair_end))?;

let scaled_point = G2Projective::mul(point, scalar);
Expand All @@ -1370,7 +1332,7 @@ pub fn bls12_g2msm(
};

let mut padded_result = Vec::new();
// The crate bls12_381 deserialize the G2 point as x_2 || x_1 || y_2 || y_1
// The crate bls12_381 deserialize the G2 point as x_1 || x_0 || y_1 || y_0
// https://docs.rs/bls12_381/0.8.0/src/bls12_381/g2.rs.html#284-299
add_padded_coordinate(&mut padded_result, result_bytes.get(48..96))?;
add_padded_coordinate(&mut padded_result, result_bytes.get(0..48))?;
Expand Down Expand Up @@ -1419,7 +1381,15 @@ fn parse_coordinate(coordinate_raw_bytes: Option<&[u8]>) -> Result<[u8; 48], VME
.map_err(|_| VMError::PrecompileError(PrecompileError::ParsingInputError))
}

fn parse_g1_point(x: [u8; 48], y: [u8; 48], unchecked: bool) -> Result<G1Projective, VMError> {
fn parse_g1_point(
point_raw_bytes: Option<&[u8]>,
unchecked: bool,
) -> Result<G1Projective, VMError> {
let point_bytes =
point_raw_bytes.ok_or(VMError::PrecompileError(PrecompileError::ParsingInputError))?;
let x = parse_coordinate(point_bytes.get(0..64))?;
let y = parse_coordinate(point_bytes.get(64..128))?;

// if a g1 point decode to (0,0) by convention it is interpreted as a point to infinity
let g1_point: G1Projective = if x.iter().all(|e| *e == 0) && y.iter().all(|e| *e == 0) {
G1Projective::identity()
Expand Down Expand Up @@ -1456,23 +1426,27 @@ fn parse_g1_point(x: [u8; 48], y: [u8; 48], unchecked: bool) -> Result<G1Project
}

fn parse_g2_point(
x_1: [u8; 48],
x_2: [u8; 48],
y_1: [u8; 48],
y_2: [u8; 48],
point_raw_bytes: Option<&[u8]>,
unchecked: bool,
) -> Result<G2Projective, VMError> {
let point_bytes =
point_raw_bytes.ok_or(VMError::PrecompileError(PrecompileError::ParsingInputError))?;
let x_0 = parse_coordinate(point_bytes.get(0..64))?;
let x_1 = parse_coordinate(point_bytes.get(64..128))?;
let y_0 = parse_coordinate(point_bytes.get(128..192))?;
let y_1 = parse_coordinate(point_bytes.get(192..256))?;

// if a g1 point decode to (0,0) by convention it is interpreted as a point to infinity
let g2_point: G2Projective = if x_1.iter().all(|e| *e == 0)
&& x_2.iter().all(|e| *e == 0)
let g2_point: G2Projective = if x_0.iter().all(|e| *e == 0)
&& x_1.iter().all(|e| *e == 0)
&& y_0.iter().all(|e| *e == 0)
&& y_1.iter().all(|e| *e == 0)
&& y_2.iter().all(|e| *e == 0)
{
G2Projective::identity()
} else {
// The crate serialize the coordinates in a reverse order
// https://docs.rs/bls12_381/0.8.0/src/bls12_381/g2.rs.html#401-464
let g2_bytes: [u8; 192] = [x_2, x_1, y_2, y_1]
let g2_bytes: [u8; 192] = [x_1, x_0, y_1, y_0]
.concat()
.try_into()
.map_err(|_| VMError::Internal(InternalError::ConversionError))?;
Expand Down

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