ethereum.prague.vm.precompiled_contracts.bls12_381.bls12_381_pairing

Ethereum Virtual Machine (EVM) BLS12 381 PAIRING PRE-COMPILE ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. contents:: Table of Contents :backlinks: none :local:

Introduction

Implementation of the BLS12 381 pairing pre-compile.

bls12_pairing

The bls12_381 pairing precompile.

Parameters

evm : The current EVM frame.

Raises

InvalidParameter If the input length is invalid or if sub-group check fails.

def bls12_pairing(​evm: Evm​) -> None:
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    """
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    The bls12_381 pairing precompile.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    Raises
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    ------
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    InvalidParameter
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        If the input length is invalid or if sub-group check fails.
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    """
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    data = evm.message.data
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    if len(data) == 0 or len(data) % 384 != 0:
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        raise InvalidParameter("Invalid Input Length")
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    # GAS
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    k = len(data) // 384
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    gas_cost = Uint(32600 * k + 37700)
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    charge_gas(evm, gas_cost)
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    # OPERATION
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    result = FQ12.one()
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    for i in range(k):
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        g1_start = Uint(384 * i)
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        g2_start = Uint(384 * i + 128)
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        g1_slice = data[g1_start : g1_start + Uint(128)]
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        g1_point = bytes_to_g1(bytes(g1_slice))
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        if not is_inf(bls12_multiply(g1_point, curve_order)):
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            raise InvalidParameter("Sub-group check failed for G1 point.")
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        g2_slice = data[g2_start : g2_start + Uint(256)]
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        g2_point = bytes_to_g2(bytes(g2_slice))
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        if not is_inf(bls12_multiply(g2_point, curve_order)):
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            raise InvalidParameter("Sub-group check failed for G2 point.")
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        result *= pairing(g2_point, g1_point)
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    if result == FQ12.one():
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        evm.output = b"\x00" * 31 + b"\x01"
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    else:
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        evm.output = b"\x00" * 32