|
| 1 | +use core::str::FromStr; |
| 2 | + |
| 3 | +use super::{ |
| 4 | + hint_utils::get_relocatable_from_var_name, |
| 5 | + secp::{bigint_utils::BigInt3, secp_utils::SECP_P}, |
| 6 | +}; |
| 7 | +use crate::{ |
| 8 | + hint_processor::hint_processor_definition::HintReference, |
| 9 | + serde::deserialize_program::ApTracking, |
| 10 | + types::relocatable::MaybeRelocatable, |
| 11 | + vm::{errors::hint_errors::HintError, vm_core::VirtualMachine}, |
| 12 | + Felt252, |
| 13 | +}; |
| 14 | +use crate::{ |
| 15 | + stdlib::{collections::HashMap, ops::Deref, prelude::*}, |
| 16 | + types::exec_scope::ExecutionScopes, |
| 17 | +}; |
| 18 | +use lazy_static::lazy_static; |
| 19 | +use num_bigint::BigInt; |
| 20 | +use num_integer::Integer; |
| 21 | +use num_traits::FromPrimitive; |
| 22 | +use num_traits::Zero; |
| 23 | + |
| 24 | +lazy_static! { |
| 25 | + static ref BLS_BASE: BigInt = BigInt::from_u64(2).unwrap().pow(86); |
| 26 | + static ref BLS_PRIME: BigInt = BigInt::from_str( |
| 27 | + "52435875175126190479447740508185965837690552500527637822603658699938581184513" |
| 28 | + ) |
| 29 | + .unwrap(); |
| 30 | +} |
| 31 | +pub const WRITE_DIVMOD_SEGMENT: &str = r#"from starkware.starknet.core.os.data_availability.bls_utils import BLS_PRIME, pack, split |
| 32 | +
|
| 33 | +a = pack(ids.a, PRIME) |
| 34 | +b = pack(ids.b, PRIME) |
| 35 | +
|
| 36 | +q, r = divmod(a * b, BLS_PRIME) |
| 37 | +
|
| 38 | +# By the assumption: |a|, |b| < 2**104 * ((2**86) ** 2 + 2**86 + 1) < 2**276.001. |
| 39 | +# Therefore |q| <= |ab| / BLS_PRIME < 2**299. |
| 40 | +# Hence the absolute value of the high limb of split(q) < 2**127. |
| 41 | +segments.write_arg(ids.q.address_, split(q)) |
| 42 | +segments.write_arg(ids.res.address_, split(r))"#; |
| 43 | + |
| 44 | +pub fn write_div_mod_segment( |
| 45 | + vm: &mut VirtualMachine, |
| 46 | + _exec_scopes: &mut ExecutionScopes, |
| 47 | + ids_data: &HashMap<String, HintReference>, |
| 48 | + ap_tracking: &ApTracking, |
| 49 | + _constants: &HashMap<String, Felt252>, |
| 50 | +) -> Result<(), HintError> { |
| 51 | + let a = bls_pack( |
| 52 | + &BigInt3::from_var_name("a", vm, ids_data, ap_tracking)?, |
| 53 | + &SECP_P, |
| 54 | + ); |
| 55 | + let b = bls_pack( |
| 56 | + &BigInt3::from_var_name("b", vm, ids_data, ap_tracking)?, |
| 57 | + &SECP_P, |
| 58 | + ); |
| 59 | + let (q, r) = (a * b).div_mod_floor(&BLS_PRIME); |
| 60 | + let q_reloc = get_relocatable_from_var_name("q", vm, ids_data, ap_tracking)?; |
| 61 | + let res_reloc = get_relocatable_from_var_name("res", vm, ids_data, ap_tracking)?; |
| 62 | + |
| 63 | + let q_arg: Vec<MaybeRelocatable> = bls_split(q) |
| 64 | + .into_iter() |
| 65 | + .map(|ref n| Felt252::from(n).into()) |
| 66 | + .collect::<Vec<MaybeRelocatable>>(); |
| 67 | + let res_arg: Vec<MaybeRelocatable> = bls_split(r) |
| 68 | + .into_iter() |
| 69 | + .map(|ref n| Felt252::from(n).into()) |
| 70 | + .collect::<Vec<MaybeRelocatable>>(); |
| 71 | + vm.write_arg(q_reloc, &q_arg).map_err(HintError::Memory)?; |
| 72 | + vm.write_arg(res_reloc, &res_arg) |
| 73 | + .map_err(HintError::Memory)?; |
| 74 | + Ok(()) |
| 75 | +} |
| 76 | + |
| 77 | +fn bls_split(mut num: BigInt) -> Vec<BigInt> { |
| 78 | + use num_traits::Signed; |
| 79 | + let mut a = Vec::new(); |
| 80 | + for _ in 0..2 { |
| 81 | + let residue = &num % BLS_BASE.deref(); |
| 82 | + num /= BLS_BASE.deref(); |
| 83 | + a.push(residue); |
| 84 | + } |
| 85 | + assert!(num.abs() < BigInt::from_u128(1 << 127).unwrap()); |
| 86 | + a.push(num); |
| 87 | + a |
| 88 | +} |
| 89 | + |
| 90 | +fn as_int(value: BigInt, prime: &BigInt) -> BigInt { |
| 91 | + let half_prime = prime / 2u32; |
| 92 | + if value > half_prime { |
| 93 | + value - prime |
| 94 | + } else { |
| 95 | + value |
| 96 | + } |
| 97 | +} |
| 98 | + |
| 99 | +fn bls_pack(z: &BigInt3, prime: &BigInt) -> BigInt { |
| 100 | + let limbs = &z.limbs; |
| 101 | + limbs |
| 102 | + .iter() |
| 103 | + .enumerate() |
| 104 | + .fold(BigInt::zero(), |acc, (i, limb)| { |
| 105 | + let limb_as_int = as_int(limb.to_bigint(), prime); |
| 106 | + acc + limb_as_int * &BLS_BASE.pow(i as u32) |
| 107 | + }) |
| 108 | +} |
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