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chore: mitigate copies in final_exponentiation #12

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May 16, 2024
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chore: mitigate copies in final_exponentiation #12

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84 changes: 73 additions & 11 deletions src/fp12.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -162,6 +162,44 @@ impl Fp12 {
}
}

#[inline]
#[cfg(target_os = "zkvm")]
pub fn mul_inp(&mut self, other: &Fp12) {
let aa = self.c0 * other.c0;
let bb = self.c1 * other.c1;
self.c1.add_inp(&self.c0);
let mut o = other.c0;
o.add_inp(&other.c1);
self.c1 *= o;
self.c1.sub_inp(&aa);
self.c1.sub_inp(&bb);
self.c0 = bb.mul_by_nonresidue_owned();
self.c0.add_inp(&aa);
}

#[inline]
fn mul(&self, other: &Fp12) -> Self {
cfg_if::cfg_if! {
if #[cfg(target_os = "zkvm")] {
let mut out = self.clone();
out.mul_inp(other);
out
} else {
let aa = self.c0 * other.c0;
let bb = self.c1 * other.c1;
let c1 = self.c1 + self.c0;
let o = other.c0 + other.c1;
let c1 = c1 * o;
let c1 = c1 - aa;
let c1 = c1 - bb;
let c0 = bb.mul_by_nonresidue();
let c0 = c0 + aa;

Fp12 { c0, c1 }
}
}
}

/// Raises this element to p.
#[inline(always)]
pub fn frobenius_map(&self) -> Self {
Expand Down Expand Up @@ -192,6 +230,40 @@ impl Fp12 {
Fp12 { c0, c1 }
}

/// Raises this element to p.
#[inline]
#[cfg(target_os = "zkvm")]
pub fn frobenius_map_inp(&mut self) {
self.c0.frobenius_map_inp();
self.c1.frobenius_map_inp();

const C1_MUL: Fp6 = Fp6 {
c0: Fp2 {
c0: Fp::from_raw_unchecked([
0x0708_9552_b319_d465,
0xc669_5f92_b50a_8313,
0x97e8_3ccc_d117_228f,
0xa35b_aeca_b2dc_29ee,
0x1ce3_93ea_5daa_ce4d,
0x08f2_220f_b0fb_66eb,
]),
c1: Fp::from_raw_unchecked([
0xb2f6_6aad_4ce5_d646,
0x5842_a06b_fc49_7cec,
0xcf48_95d4_2599_d394,
0xc11b_9cba_40a8_e8d0,
0x2e38_13cb_e5a0_de89,
0x110e_efda_8884_7faf,
]),
},
c1: Fp2::zero(),
c2: Fp2::zero(),
};

// c1 = c1 * (u + 1)^((p - 1) / 6)
self.c1 *= C1_MUL;
}

#[inline]
#[cfg(target_os = "zkvm")]
pub fn square(&self) -> Self {
Expand Down Expand Up @@ -237,17 +309,7 @@ impl<'a, 'b> Mul<&'b Fp12> for &'a Fp12 {

#[inline]
fn mul(self, other: &'b Fp12) -> Self::Output {
let aa = self.c0 * other.c0;
let bb = self.c1 * other.c1;
let o = other.c0 + other.c1;
let c1 = self.c1 + self.c0;
let c1 = c1 * o;
let c1 = c1 - aa;
let c1 = c1 - bb;
let c0 = bb.mul_by_nonresidue();
let c0 = c0 + aa;

Fp12 { c0, c1 }
self.mul(other)
}
}

Expand Down
13 changes: 13 additions & 0 deletions src/fp2.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,14 @@ impl Fp2 {
self.conjugate()
}

/// Raises this element to p.
#[inline]
pub fn frobenius_map_inp(&mut self) {
// This is always just a conjugation. If you're curious why, here's
// an article about it: https://alicebob.cryptoland.net/the-frobenius-endomorphism-with-finite-fields/
self.conjugate_inp()
}

#[inline(always)]
pub fn conjugate(&self) -> Self {
Fp2 {
Expand All @@ -161,6 +169,11 @@ impl Fp2 {
}
}

#[inline]
pub fn conjugate_inp(&mut self) {
self.c1 = -self.c1;
}

#[inline]
#[cfg(target_os = "zkvm")]
pub fn mul_by_nonresidue_inp(&mut self) {
Expand Down
77 changes: 73 additions & 4 deletions src/fp6.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -165,6 +165,23 @@ impl Fp6 {
}
}

/// Multiply by quadratic nonresidue v.
#[cfg(target_os = "zkvm")]
pub fn mul_by_nonresidue_owned(self) -> Self {
// Given a + bv + cv^2, this produces
// av + bv^2 + cv^3
// but because v^3 = u + 1, we have
// c(u + 1) + av + v^2
let Fp6 { c0, c1, mut c2 } = self;
c2.mul_by_nonresidue_inp();

Fp6 {
c0: c2,
c1: c0,
c2: c1,
}
}

/// Raises this element to p.
#[inline(always)]
pub fn frobenius_map(&self) -> Self {
Expand Down Expand Up @@ -203,6 +220,45 @@ impl Fp6 {
Fp6 { c0, c1, c2 }
}

/// Raises this element to p.
#[inline]
#[cfg(target_os = "zkvm")]
pub fn frobenius_map_inp(&mut self) {
self.c0.frobenius_map_inp();
self.c1.frobenius_map_inp();
self.c2.frobenius_map_inp();

const C1_MUL: Fp2 = Fp2 {
c0: Fp::zero(),
c1: Fp::from_raw_unchecked([
0xcd03_c9e4_8671_f071,
0x5dab_2246_1fcd_a5d2,
0x5870_42af_d385_1b95,
0x8eb6_0ebe_01ba_cb9e,
0x03f9_7d6e_83d0_50d2,
0x18f0_2065_5463_8741,
]),
};

const C2_MUL: Fp2 = Fp2 {
c0: Fp::from_raw_unchecked([
0x890d_c9e4_8675_45c3,
0x2af3_2253_3285_a5d5,
0x5088_0866_309b_7e2c,
0xa20d_1b8c_7e88_1024,
0x14e4_f04f_e2db_9068,
0x14e5_6d3f_1564_853a,
]),
c1: Fp::zero(),
};

// c1 = c1 * (u + 1)^((p - 1) / 3)
self.c1.mul_inp(&C1_MUL);

// c2 = c2 * (u + 1)^((2p - 2) / 3)
self.c2.mul_inp(&C2_MUL);
}

#[inline(always)]
pub fn is_zero(&self) -> Choice {
self.c0.is_zero() & self.c1.is_zero() & self.c2.is_zero()
Expand Down Expand Up @@ -250,10 +306,23 @@ impl Fp6 {
// Each of these is a "sum of products", which we can compute efficiently.

let a = self;
let b10_p_b11 = b.c1.c0 + b.c1.c1;
let b10_m_b11 = b.c1.c0 - b.c1.c1;
let b20_p_b21 = b.c2.c0 + b.c2.c1;
let b20_m_b21 = b.c2.c0 - b.c2.c1;
cfg_if::cfg_if! {
if #[cfg(target_os = "zkvm")] {
let mut b10_p_b11 = b.c1.c0;
b10_p_b11.add_inp(&b.c1.c1);
let mut b10_m_b11 = b.c1.c0;
b10_m_b11.sub_inp(&b.c1.c1);
let mut b20_p_b21 = b.c2.c0;
b20_p_b21.add_inp(&b.c2.c1);
let mut b20_m_b21 = b.c2.c0;
b20_m_b21.sub_inp(&b.c2.c1)
} else {
let b10_p_b11 = b.c1.c0 + b.c1.c1;
let b10_m_b11 = b.c1.c0 - b.c1.c1;
let b20_p_b21 = b.c2.c0 + b.c2.c1;
let b20_m_b21 = b.c2.c0 - b.c2.c1;
}
}

Fp6 {
c0: Fp2 {
Expand Down
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