ethereum.forks.amsterdam.vm.precompiled_contracts.bls12_381.bls12_381_g1

Ethereum Virtual Machine (EVM) BLS12 381 CONTRACTS.

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

Introduction

Implementation of pre-compiles in G1 (curve over base prime field).

LENGTH_PER_PAIR

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LENGTH_PER_PAIR = 160

bls12_g1_add

The bls12_381 G1 point addition precompile.

Parameters

evm : The current EVM frame.

Raises

InvalidParameter If the input length is invalid.

def bls12_g1_add(​evm: Evm​) -> None:
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    <snip>
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    data = evm.call_data
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    if len(data) != 256:
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        raise InvalidParameter("Invalid Input Length")
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    # GAS
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    charge_gas(evm, GasCosts.PRECOMPILE_BLS_G1ADD)
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    # OPERATION
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    p1 = bytes_to_g1(buffer_read(data, U256(0), U256(128)))
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    p2 = bytes_to_g1(buffer_read(data, U256(128), U256(128)))
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    result = bls12_add(p1, p2)
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    evm.output = g1_to_bytes(result)

bls12_g1_msm

The bls12_381 G1 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_g1_msm(​evm: Evm​) -> None:
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    <snip>
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    data = evm.call_data
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    if len(data) == 0 or len(data) % LENGTH_PER_PAIR != 0:
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        raise InvalidParameter("Invalid Input Length")
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    # GAS
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    k = len(data) // LENGTH_PER_PAIR
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    if k <= 128:
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        discount = Uint(G1_K_DISCOUNT[k - 1])
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    else:
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        discount = Uint(G1_MAX_DISCOUNT)
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    gas_cost = ExecutionGas(
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        Uint(k) * GasCosts.PRECOMPILE_BLS_G1MUL * discount // MULTIPLIER
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    )
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    charge_gas(evm, gas_cost)
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    # OPERATION
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    for i in range(k):
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        start_index = i * LENGTH_PER_PAIR
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        end_index = start_index + LENGTH_PER_PAIR
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        p, m = decode_g1_scalar_pair(data[start_index:end_index])
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        product = bls12_multiply(p, m)
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        if i == 0:
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            result = product
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        else:
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            result = bls12_add(result, product)
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    evm.output = g1_to_bytes(result)

bls12_map_fp_to_g1

Precompile to map field element to G1.

Parameters

evm : The current EVM frame.

Raises

InvalidParameter If the input length is invalid.

def bls12_map_fp_to_g1(​evm: Evm​) -> None:
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    <snip>
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    data = evm.call_data
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    if len(data) != 64:
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        raise InvalidParameter("Invalid Input Length")
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    # GAS
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    charge_gas(evm, GasCosts.PRECOMPILE_BLS_G1MAP)
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    # OPERATION
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    fp = int.from_bytes(data, "big")
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    if fp >= FQ.field_modulus:
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        raise InvalidParameter("coordinate >= field modulus")
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    g1_optimized_3d = clear_cofactor_G1(map_to_curve_G1(FQ(fp)))
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    evm.output = g1_to_bytes(g1_optimized_3d)