process scalar_to_epns digits 2 by 2 to avoid dealing with alternating scalar_negative bool (-30%) (#324)

Author: feltroidprime

hydra/garaga/starknet/groth16_contract_generator/generator.py

@@ -8,7 +8,7 @@
 from garaga.starknet.cli.utils import create_directory, get_package_version
 from garaga.starknet.groth16_contract_generator.parsing_utils import Groth16VerifyingKey
 
-ECIP_OPS_CLASS_HASH = 0x54234B153BAA38A35C69A075C50F3F868B3436A60AE5D19E1A7687E716B30F7
+ECIP_OPS_CLASS_HASH = 0x25387ED45CD336DBDCA62F1EEC9AC2A393EFA68AE197843CBD1BC7F15CBF1B3
 CAIRO_VERSION = "2.11.2"
 
 

src/contracts/groth16_example_bls12_381/src/groth16_verifier.cairo

@@ -18,7 +18,7 @@ mod Groth16VerifierBLS12_381 {
     use super::{N_PUBLIC_INPUTS, ic, precomputed_lines, vk};
 
     const ECIP_OPS_CLASS_HASH: felt252 =
-        0x54234b153baa38a35c69a075c50f3f868b3436a60ae5d19e1a7687e716b30f7;
+        0x25387ed45cd336dbdca62f1eec9ac2a393efa68ae197843cbd1bc7f15cbf1b3;
 
     #[storage]
     struct Storage {}

src/contracts/groth16_example_bn254/src/groth16_verifier.cairo

@@ -18,7 +18,7 @@ mod Groth16VerifierBN254 {
     use super::{N_PUBLIC_INPUTS, ic, precomputed_lines, vk};
 
     const ECIP_OPS_CLASS_HASH: felt252 =
-        0x54234b153baa38a35c69a075c50f3f868b3436a60ae5d19e1a7687e716b30f7;
+        0x25387ed45cd336dbdca62f1eec9ac2a393efa68ae197843cbd1bc7f15cbf1b3;
 
     #[storage]
     struct Storage {}

src/contracts/risc0_sample_app/fibonacci_sequencer/src/lib.cairo

@@ -11,7 +11,7 @@ mod FibonacciSequencer {
     use core::starknet::storage::{StoragePointerReadAccess, StoragePointerWriteAccess};
 
     pub const RISC_ZERO_VERIFIER_CLASS_HASH: felt252 =
-        0x69048809c792c02edfcdb2237889207a89cd030ec0dd7a8c763e21453ff51a8;
+        0x5c3032adf35586059bcbf2ab30aaf42f024eff74a0a5f43196d194f2db93402;
 
     #[storage]
     struct Storage {

src/contracts/risc0_verifier_bn254/src/groth16_verifier.cairo

@@ -19,7 +19,7 @@ mod Risc0Groth16VerifierBN254 {
     use super::{N_FREE_PUBLIC_INPUTS, T, ic, precomputed_lines, vk};
 
     const ECIP_OPS_CLASS_HASH: felt252 =
-        0x54234b153baa38a35c69a075c50f3f868b3436a60ae5d19e1a7687e716b30f7;
+        0x25387ed45cd336dbdca62f1eec9ac2a393efa68ae197843cbd1bc7f15cbf1b3;
 
     #[storage]
     struct Storage {}

src/src/utils/neg_3.cairo

@@ -25,49 +25,6 @@ pub fn sign_to_u384(sign: felt252, curve_index: usize) -> u384 {
     }
 }
 
-// Decomposes a scalar into base -3 representation.
-// :param scalar: The integer to be decomposed.
-// :return: A list of coefficients in base -3 representation. (Least significant bit first),
-// with digits [-1, 0, 1] such that scalar = sum((-3) ** i * d for (i, d) in enumerate(digits))
-pub fn neg_3_base_le(scalar: u128) -> Array<felt252> {
-    let mut digits: Array<felt252> = ArrayTrait::new();
-
-    if scalar == 0 {
-        digits.append(0);
-        return digits;
-    }
-
-    let mut scalar: u128 = scalar;
-
-    let mut scalar_negative: bool = false;
-
-    while scalar != 0 {
-        let (q, r) = core::traits::DivRem::div_rem(scalar, 3);
-        let r: felt252 = r.into();
-
-        if r == 2 {
-            if scalar_negative {
-                scalar = q + 1;
-                digits.append(1);
-            } else {
-                scalar = q + 1;
-                digits.append(-1);
-            }
-        } else {
-            if scalar_negative {
-                scalar = q;
-                digits.append(-r);
-            } else {
-                scalar = q;
-                digits.append(r);
-            }
-        }
-        scalar_negative = !scalar_negative;
-    }
-
-    return digits;
-}
-
 pub fn u256_array_to_low_high_epns(
     scalars: Span<u256>,
     scalars_digits_decompositions: Option<Span<(Span<felt252>, Span<felt252>)>>,
@@ -146,31 +103,35 @@ pub fn scalar_to_epns(mut scalar: u128) -> (felt252, felt252, felt252, felt252)
 
     let mut base_power = 1; // Init to (-3)^0
 
-    let mut scalar_negative: bool = false;
-
     while scalar != 0 {
-        let (q, r) = core::traits::DivRem::div_rem(scalar, 3);
-        let r: felt252 = r.into();
-        if r == 0 {
-            scalar = q;
-        } else if r == 2 {
-            if scalar_negative {
-                scalar = q + 1;
-                sum_p += base_power;
-            } else {
-                scalar = q + 1;
-                sum_n += base_power;
-            }
+        let (q0, r0) = core::traits::DivRem::div_rem(scalar, 3);
+        let r0: felt252 = r0.into();
+        if r0 == 0 {
+            scalar = q0;
+        } else if r0 == 2 {
+            scalar = q0 + 1;
+            sum_n += base_power;
         } else {
-            if scalar_negative {
-                scalar = q;
-                sum_n += base_power;
-            } else {
-                scalar = q;
-                sum_p += base_power;
-            }
+            scalar = q0;
+            sum_p += base_power;
+        }
+        if scalar == 0 {
+            break;
         }
-        scalar_negative = !scalar_negative;
+        base_power = base_power * (-3);
+        let (q1, r1) = core::traits::DivRem::div_rem(scalar, 3);
+        let r1: felt252 = r1.into();
+
+        if r1 == 0 {
+            scalar = q1;
+        } else if r1 == 2 {
+            scalar = q1 + 1;
+            sum_p += base_power;
+        } else {
+            scalar = q1;
+            sum_n += base_power;
+        }
+
         base_power = base_power * (-3);
     }
 
@@ -216,7 +177,7 @@ pub fn scalar_to_epns_with_digits(
 mod tests {
     use core::circuit::u384;
     use core::traits::TryInto;
-    use super::{neg_3_base_le, scalar_to_epns};
+    use super::scalar_to_epns;
 
     #[test]
     fn test_scalar_to_epns() {
@@ -278,13 +239,5 @@ mod tests {
         assert_eq!(sign_p, 1);
         assert_eq!(sign_n, -1);
     }
-    #[test]
-    fn test_neg_3_base_le_single() {
-        let digits: Array<felt252> = neg_3_base_le(16);
-
-        let expected: Array<felt252> = array![1, 1, -1, -1];
-
-        assert_eq!(digits, expected);
-    }
 }