1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101

use generic_array::GenericArray;
use num::{BigUint, Num, Zero};
use serde::{Deserialize, Serialize};
use typenum::{U32, U62};

use super::{SwCurve, WeierstrassParameters};
use crate::operations::field::params::FieldParameters;
use crate::operations::field::params::NumLimbs;
use crate::utils::ec::CurveType;
use crate::utils::ec::EllipticCurveParameters;

#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
/// Bn254 curve parameter
pub struct Bn254Parameters;

pub type Bn254 = SwCurve<Bn254Parameters>;

#[derive(Debug, Default, Clone, Copy, PartialEq, Serialize, Deserialize)]
/// Bn254 base field parameter
pub struct Bn254BaseField;

impl FieldParameters for Bn254BaseField {
    const MODULUS: &'static [u8] = &[
        71, 253, 124, 216, 22, 140, 32, 60, 141, 202, 113, 104, 145, 106, 129, 151, 93, 88, 129,
        129, 182, 69, 80, 184, 41, 160, 49, 225, 114, 78, 100, 48,
    ];

    // A rough witness-offset estimate given the size of the limbs and the size of the field.
    const WITNESS_OFFSET: usize = 1usize << 14;

    // The modulus has been taken from py_ecc python library by Ethereum Foundation.
    // https://github.com/ethereum/py_pairing/blob/5f609da/py_ecc/bn128/bn128_field_elements.py#L10-L11
    fn modulus() -> BigUint {
        BigUint::from_str_radix(
            "21888242871839275222246405745257275088696311157297823662689037894645226208583",
            10,
        )
        .unwrap()
    }
}

impl NumLimbs for Bn254BaseField {
    type Limbs = U32;
    type Witness = U62;
}

impl EllipticCurveParameters for Bn254Parameters {
    type BaseField = Bn254BaseField;

    const CURVE_TYPE: CurveType = CurveType::Bn254;
}

impl WeierstrassParameters for Bn254Parameters {
    // The values have been taken from py_ecc python library by Ethereum Foundation.
    // https://github.com/ethereum/py_pairing/blob/5f609da/py_ecc/bn128/bn128_field_elements.py
    const A: GenericArray<u8, U32> = GenericArray::from_array([
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0,
    ]);

    const B: GenericArray<u8, U32> = GenericArray::from_array([
        3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0,
    ]);
    fn generator() -> (BigUint, BigUint) {
        let x = BigUint::from(1u32);
        let y = BigUint::from(2u32);
        (x, y)
    }

    fn prime_group_order() -> num::BigUint {
        BigUint::from_str_radix(
            "21888242871839275222246405745257275088548364400416034343698204186575808495617",
            10,
        )
        .unwrap()
    }

    fn a_int() -> BigUint {
        BigUint::zero()
    }

    fn b_int() -> BigUint {
        BigUint::from(3u32)
    }
}

#[cfg(test)]
mod tests {

    use super::*;
    use crate::utils::ec::utils::biguint_from_limbs;

    #[test]
    fn test_weierstrass_biguint_scalar_mul() {
        assert_eq!(
            biguint_from_limbs(Bn254BaseField::MODULUS),
            Bn254BaseField::modulus()
        );
    }
}