ethereum.forks.bpo4.vm.precompiled_contracts.bls12_381.bls12_381_g2ethereum.forks.bpo5.vm.precompiled_contracts.bls12_381.bls12_381_g2
Ethereum Virtual Machine (EVM) BLS12 381 G2 CONTRACTS.
.. contents:: Table of Contents :backlinks: none :local:
Introduction
Implementation of pre-compiles in G2 (curve over base prime field).
LENGTH_PER_PAIR¶
| 39 | LENGTH_PER_PAIR = 288 |
|---|
bls12_g2_add ¶
The bls12_381 G2 point addition precompile.
Parameters
evm : The current EVM frame.
Raises
InvalidParameter If the input length is invalid.
def bls12_g2_add(evm: Evm) -> None:
| 43 | <snip> |
|---|---|
| 57 | data = evm.message.data |
| 58 | if len(data) != 512: |
| 59 | raise InvalidParameter("Invalid Input Length") |
| 60 | |
| 61 | # GAS |
| 62 | charge_gas(evm, GasCosts.PRECOMPILE_BLS_G2ADD) |
| 63 | |
| 64 | # OPERATION |
| 65 | p1 = bytes_to_g2(buffer_read(data, U256(0), U256(256))) |
| 66 | p2 = bytes_to_g2(buffer_read(data, U256(256), U256(256))) |
| 67 | |
| 68 | result = bls12_add(p1, p2) |
| 69 | |
| 70 | evm.output = g2_to_bytes(result) |
bls12_g2_msm ¶
The bls12_381 G2 multi-scalar multiplication precompile. Note: This uses the naive approach to multi-scalar multiplication which is not suitably optimized for production clients. Clients are required to implement a more efficient algorithm such as the Pippenger algorithm.
Parameters
evm : The current EVM frame.
Raises
InvalidParameter If the input length is invalid.
def bls12_g2_msm(evm: Evm) -> None:
| 74 | <snip> |
|---|---|
| 92 | data = evm.message.data |
| 93 | if len(data) == 0 or len(data) % LENGTH_PER_PAIR != 0: |
| 94 | raise InvalidParameter("Invalid Input Length") |
| 95 | |
| 96 | # GAS |
| 97 | k = len(data) // LENGTH_PER_PAIR |
| 98 | if k <= 128: |
| 99 | discount = Uint(G2_K_DISCOUNT[k - 1]) |
| 100 | else: |
| 101 | discount = Uint(G2_MAX_DISCOUNT) |
| 102 | |
| 103 | gas_cost = Uint(k) * GasCosts.PRECOMPILE_BLS_G2MUL * discount // MULTIPLIER |
| 104 | charge_gas(evm, gas_cost) |
| 105 | |
| 106 | # OPERATION |
| 107 | for i in range(k): |
| 108 | start_index = i * LENGTH_PER_PAIR |
| 109 | end_index = start_index + LENGTH_PER_PAIR |
| 110 | |
| 111 | p, m = decode_g2_scalar_pair(data[start_index:end_index]) |
| 112 | product = bls12_multiply(p, m) |
| 113 | |
| 114 | if i == 0: |
| 115 | result = product |
| 116 | else: |
| 117 | result = bls12_add(result, product) |
| 118 | |
| 119 | evm.output = g2_to_bytes(result) |
bls12_map_fp2_to_g2 ¶
Precompile to map field element to G2.
Parameters
evm : The current EVM frame.
Raises
InvalidParameter If the input length is invalid.
def bls12_map_fp2_to_g2(evm: Evm) -> None:
| 123 | <snip> |
|---|---|
| 137 | data = evm.message.data |
| 138 | if len(data) != 128: |
| 139 | raise InvalidParameter("Invalid Input Length") |
| 140 | |
| 141 | # GAS |
| 142 | charge_gas(evm, GasCosts.PRECOMPILE_BLS_G2MAP) |
| 143 | |
| 144 | # OPERATION |
| 145 | field_element = bytes_to_fq2(data) |
| 146 | assert isinstance(field_element, FQ2) |
| 147 | |
| 148 | fp2 = bytes_to_fq2(data) |
| 149 | g2_3d = clear_cofactor_G2(map_to_curve_G2(fp2)) |
| 150 | |
| 151 | evm.output = g2_to_bytes(g2_3d) |