623 lines
22 KiB
Markdown
623 lines
22 KiB
Markdown
# Deneb -- Polynomial Commitments
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## Table of contents
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<!-- TOC -->
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<!-- START doctoc generated TOC please keep comment here to allow auto update -->
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<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
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- [Introduction](#introduction)
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- [Custom types](#custom-types)
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- [Constants](#constants)
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- [Preset](#preset)
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- [Blob](#blob)
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- [Trusted setup](#trusted-setup)
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- [Helper functions](#helper-functions)
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- [Bit-reversal permutation](#bit-reversal-permutation)
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- [`is_power_of_two`](#is_power_of_two)
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- [`reverse_bits`](#reverse_bits)
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- [`bit_reversal_permutation`](#bit_reversal_permutation)
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- [BLS12-381 helpers](#bls12-381-helpers)
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- [`multi_exp`](#multi_exp)
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- [`hash_to_bls_field`](#hash_to_bls_field)
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- [`bytes_to_bls_field`](#bytes_to_bls_field)
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- [`bls_field_to_bytes`](#bls_field_to_bytes)
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- [`validate_kzg_g1`](#validate_kzg_g1)
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- [`bytes_to_kzg_commitment`](#bytes_to_kzg_commitment)
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- [`bytes_to_kzg_proof`](#bytes_to_kzg_proof)
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- [`blob_to_polynomial`](#blob_to_polynomial)
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- [`compute_challenge`](#compute_challenge)
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- [`bls_modular_inverse`](#bls_modular_inverse)
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- [`div`](#div)
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- [`g1_lincomb`](#g1_lincomb)
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- [`compute_powers`](#compute_powers)
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- [`compute_roots_of_unity`](#compute_roots_of_unity)
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- [Polynomials](#polynomials)
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- [`evaluate_polynomial_in_evaluation_form`](#evaluate_polynomial_in_evaluation_form)
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- [KZG](#kzg)
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- [`blob_to_kzg_commitment`](#blob_to_kzg_commitment)
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- [`verify_kzg_proof`](#verify_kzg_proof)
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- [`verify_kzg_proof_impl`](#verify_kzg_proof_impl)
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- [`verify_kzg_proof_batch`](#verify_kzg_proof_batch)
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- [`compute_kzg_proof`](#compute_kzg_proof)
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- [`compute_quotient_eval_within_domain`](#compute_quotient_eval_within_domain)
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- [`compute_kzg_proof_impl`](#compute_kzg_proof_impl)
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- [`compute_blob_kzg_proof`](#compute_blob_kzg_proof)
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- [`verify_blob_kzg_proof`](#verify_blob_kzg_proof)
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- [`verify_blob_kzg_proof_batch`](#verify_blob_kzg_proof_batch)
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<!-- END doctoc generated TOC please keep comment here to allow auto update -->
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<!-- /TOC -->
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## Introduction
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This document specifies basic polynomial operations and KZG polynomial commitment operations that are essential for the implementation of the EIP-4844 feature in the Deneb specification. The implementations are not optimized for performance, but readability. All practical implementations should optimize the polynomial operations.
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Functions flagged as "Public method" MUST be provided by the underlying KZG library as public functions. All other functions are private functions used internally by the KZG library.
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Public functions MUST accept raw bytes as input and perform the required cryptographic normalization before invoking any internal functions.
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## Custom types
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| Name | SSZ equivalent | Description |
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| - | - | - |
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| `G1Point` | `Bytes48` | |
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| `G2Point` | `Bytes96` | |
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| `BLSFieldElement` | `uint256` | Validation: `x < BLS_MODULUS` |
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| `KZGCommitment` | `Bytes48` | Validation: Perform [BLS standard's](https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-bls-signature-04#section-2.5) "KeyValidate" check but do allow the identity point |
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| `KZGProof` | `Bytes48` | Same as for `KZGCommitment` |
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| `Polynomial` | `Vector[BLSFieldElement, FIELD_ELEMENTS_PER_BLOB]` | A polynomial in evaluation form |
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| `Blob` | `ByteVector[BYTES_PER_FIELD_ELEMENT * FIELD_ELEMENTS_PER_BLOB]` | A basic data blob |
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## Constants
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| Name | Value | Notes |
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| - | - | - |
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| `BLS_MODULUS` | `52435875175126190479447740508185965837690552500527637822603658699938581184513` | Scalar field modulus of BLS12-381 |
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| `BYTES_PER_COMMITMENT` | `uint64(48)` | The number of bytes in a KZG commitment |
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| `BYTES_PER_PROOF` | `uint64(48)` | The number of bytes in a KZG proof |
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| `BYTES_PER_FIELD_ELEMENT` | `uint64(32)` | Bytes used to encode a BLS scalar field element |
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| `BYTES_PER_BLOB` | `uint64(BYTES_PER_FIELD_ELEMENT * FIELD_ELEMENTS_PER_BLOB)` | The number of bytes in a blob |
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| `G1_POINT_AT_INFINITY` | `Bytes48(b'\xc0' + b'\x00' * 47)` | Serialized form of the point at infinity on the G1 group |
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| `KZG_ENDIANNESS` | `'big'` | The endianness of the field elements including blobs |
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| `PRIMITIVE_ROOT_OF_UNITY` | `7` | The primitive root of unity from which all roots of unity should be derived |
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## Preset
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### Blob
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| Name | Value |
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| - | - |
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| `FIELD_ELEMENTS_PER_BLOB` | `uint64(4096)` |
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| `FIAT_SHAMIR_PROTOCOL_DOMAIN` | `b'FSBLOBVERIFY_V1_'` |
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| `RANDOM_CHALLENGE_KZG_BATCH_DOMAIN` | `b'RCKZGBATCH___V1_'` |
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### Trusted setup
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| Name | Value |
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| - | - |
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| `KZG_SETUP_G2_LENGTH` | `65` |
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| `KZG_SETUP_G1_MONOMIAL` | `Vector[G1Point, FIELD_ELEMENTS_PER_BLOB]` |
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| `KZG_SETUP_G1_LAGRANGE` | `Vector[G1Point, FIELD_ELEMENTS_PER_BLOB]` |
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| `KZG_SETUP_G2_MONOMIAL` | `Vector[G2Point, KZG_SETUP_G2_LENGTH]` |
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## Helper functions
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### Bit-reversal permutation
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All polynomials (which are always given in Lagrange form) should be interpreted as being in
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bit-reversal permutation. In practice, clients can implement this by storing the lists
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`KZG_SETUP_G1_LAGRANGE` and roots of unity in bit-reversal permutation, so these functions only
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have to be called once at startup.
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#### `is_power_of_two`
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```python
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def is_power_of_two(value: int) -> bool:
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"""
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Check if ``value`` is a power of two integer.
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"""
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return (value > 0) and (value & (value - 1) == 0)
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```
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#### `reverse_bits`
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```python
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def reverse_bits(n: int, order: int) -> int:
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"""
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Reverse the bit order of an integer ``n``.
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"""
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assert is_power_of_two(order)
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# Convert n to binary with the same number of bits as "order" - 1, then reverse its bit order
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return int(('{:0' + str(order.bit_length() - 1) + 'b}').format(n)[::-1], 2)
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```
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#### `bit_reversal_permutation`
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```python
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def bit_reversal_permutation(sequence: Sequence[T]) -> Sequence[T]:
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"""
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Return a copy with bit-reversed permutation. The permutation is an involution (inverts itself).
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The input and output are a sequence of generic type ``T`` objects.
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"""
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return [sequence[reverse_bits(i, len(sequence))] for i in range(len(sequence))]
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```
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### BLS12-381 helpers
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#### `multi_exp`
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This function performs a multi-scalar multiplication between `points` and `integers`. `points` can either be in G1 or G2.
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```python
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def multi_exp(points: Sequence[TPoint],
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integers: Sequence[uint64]) -> Sequence[TPoint]:
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# pylint: disable=unused-argument
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...
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```
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#### `hash_to_bls_field`
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```python
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def hash_to_bls_field(data: bytes) -> BLSFieldElement:
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"""
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Hash ``data`` and convert the output to a BLS scalar field element.
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The output is not uniform over the BLS field.
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"""
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hashed_data = hash(data)
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return BLSFieldElement(int.from_bytes(hashed_data, KZG_ENDIANNESS) % BLS_MODULUS)
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```
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#### `bytes_to_bls_field`
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```python
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def bytes_to_bls_field(b: Bytes32) -> BLSFieldElement:
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"""
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Convert untrusted bytes to a trusted and validated BLS scalar field element.
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This function does not accept inputs greater than the BLS modulus.
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"""
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field_element = int.from_bytes(b, KZG_ENDIANNESS)
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assert field_element < BLS_MODULUS
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return BLSFieldElement(field_element)
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```
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#### `bls_field_to_bytes`
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```python
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def bls_field_to_bytes(x: BLSFieldElement) -> Bytes32:
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return int.to_bytes(x % BLS_MODULUS, 32, KZG_ENDIANNESS)
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```
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#### `validate_kzg_g1`
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```python
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def validate_kzg_g1(b: Bytes48) -> None:
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"""
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Perform BLS validation required by the types `KZGProof` and `KZGCommitment`.
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"""
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if b == G1_POINT_AT_INFINITY:
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return
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assert bls.KeyValidate(b)
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```
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#### `bytes_to_kzg_commitment`
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```python
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def bytes_to_kzg_commitment(b: Bytes48) -> KZGCommitment:
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"""
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Convert untrusted bytes into a trusted and validated KZGCommitment.
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"""
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validate_kzg_g1(b)
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return KZGCommitment(b)
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```
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#### `bytes_to_kzg_proof`
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```python
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def bytes_to_kzg_proof(b: Bytes48) -> KZGProof:
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"""
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Convert untrusted bytes into a trusted and validated KZGProof.
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"""
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validate_kzg_g1(b)
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return KZGProof(b)
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```
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#### `blob_to_polynomial`
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```python
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def blob_to_polynomial(blob: Blob) -> Polynomial:
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"""
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Convert a blob to list of BLS field scalars.
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"""
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polynomial = Polynomial()
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for i in range(FIELD_ELEMENTS_PER_BLOB):
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value = bytes_to_bls_field(blob[i * BYTES_PER_FIELD_ELEMENT: (i + 1) * BYTES_PER_FIELD_ELEMENT])
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polynomial[i] = value
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return polynomial
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```
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#### `compute_challenge`
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```python
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def compute_challenge(blob: Blob,
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commitment: KZGCommitment) -> BLSFieldElement:
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"""
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Return the Fiat-Shamir challenge required by the rest of the protocol.
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"""
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# Append the degree of the polynomial as a domain separator
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degree_poly = int.to_bytes(FIELD_ELEMENTS_PER_BLOB, 16, KZG_ENDIANNESS)
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data = FIAT_SHAMIR_PROTOCOL_DOMAIN + degree_poly
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data += blob
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data += commitment
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# Transcript has been prepared: time to create the challenge
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return hash_to_bls_field(data)
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```
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#### `bls_modular_inverse`
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```python
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def bls_modular_inverse(x: BLSFieldElement) -> BLSFieldElement:
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"""
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Compute the modular inverse of x (for x != 0)
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i.e. return y such that x * y % BLS_MODULUS == 1
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"""
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assert (int(x) % BLS_MODULUS) != 0
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return BLSFieldElement(pow(x, -1, BLS_MODULUS))
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```
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#### `div`
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```python
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def div(x: BLSFieldElement, y: BLSFieldElement) -> BLSFieldElement:
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"""
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Divide two field elements: ``x`` by `y``.
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"""
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return BLSFieldElement((int(x) * int(bls_modular_inverse(y))) % BLS_MODULUS)
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```
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#### `g1_lincomb`
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```python
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def g1_lincomb(points: Sequence[KZGCommitment], scalars: Sequence[BLSFieldElement]) -> KZGCommitment:
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"""
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BLS multiscalar multiplication in G1. This can be naively implemented using double-and-add.
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"""
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assert len(points) == len(scalars)
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if len(points) == 0:
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return bls.G1_to_bytes48(bls.Z1())
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points_g1 = []
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for point in points:
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points_g1.append(bls.bytes48_to_G1(point))
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result = bls.multi_exp(points_g1, scalars)
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return KZGCommitment(bls.G1_to_bytes48(result))
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```
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#### `compute_powers`
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```python
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def compute_powers(x: BLSFieldElement, n: uint64) -> Sequence[BLSFieldElement]:
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"""
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Return ``x`` to power of [0, n-1], if n > 0. When n==0, an empty array is returned.
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"""
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current_power = 1
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powers = []
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for _ in range(n):
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powers.append(BLSFieldElement(current_power))
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current_power = current_power * int(x) % BLS_MODULUS
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return powers
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```
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#### `compute_roots_of_unity`
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```python
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def compute_roots_of_unity(order: uint64) -> Sequence[BLSFieldElement]:
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"""
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Return roots of unity of ``order``.
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"""
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assert (BLS_MODULUS - 1) % int(order) == 0
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root_of_unity = BLSFieldElement(pow(PRIMITIVE_ROOT_OF_UNITY, (BLS_MODULUS - 1) // int(order), BLS_MODULUS))
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return compute_powers(root_of_unity, order)
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```
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### Polynomials
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#### `evaluate_polynomial_in_evaluation_form`
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```python
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def evaluate_polynomial_in_evaluation_form(polynomial: Polynomial,
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z: BLSFieldElement) -> BLSFieldElement:
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"""
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Evaluate a polynomial (in evaluation form) at an arbitrary point ``z``.
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- When ``z`` is in the domain, the evaluation can be found by indexing the polynomial at the
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position that ``z`` is in the domain.
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- When ``z`` is not in the domain, the barycentric formula is used:
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f(z) = (z**WIDTH - 1) / WIDTH * sum_(i=0)^WIDTH (f(DOMAIN[i]) * DOMAIN[i]) / (z - DOMAIN[i])
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"""
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width = len(polynomial)
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assert width == FIELD_ELEMENTS_PER_BLOB
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inverse_width = bls_modular_inverse(BLSFieldElement(width))
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roots_of_unity_brp = bit_reversal_permutation(compute_roots_of_unity(FIELD_ELEMENTS_PER_BLOB))
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# If we are asked to evaluate within the domain, we already know the answer
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if z in roots_of_unity_brp:
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eval_index = roots_of_unity_brp.index(z)
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return BLSFieldElement(polynomial[eval_index])
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result = 0
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for i in range(width):
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a = BLSFieldElement(int(polynomial[i]) * int(roots_of_unity_brp[i]) % BLS_MODULUS)
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b = BLSFieldElement((int(BLS_MODULUS) + int(z) - int(roots_of_unity_brp[i])) % BLS_MODULUS)
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result += int(div(a, b) % BLS_MODULUS)
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result = result * int(BLS_MODULUS + pow(z, width, BLS_MODULUS) - 1) * int(inverse_width)
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return BLSFieldElement(result % BLS_MODULUS)
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```
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### KZG
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KZG core functions. These are also defined in Deneb execution specs.
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#### `blob_to_kzg_commitment`
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```python
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def blob_to_kzg_commitment(blob: Blob) -> KZGCommitment:
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"""
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Public method.
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"""
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assert len(blob) == BYTES_PER_BLOB
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return g1_lincomb(bit_reversal_permutation(KZG_SETUP_G1_LAGRANGE), blob_to_polynomial(blob))
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```
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#### `verify_kzg_proof`
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```python
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def verify_kzg_proof(commitment_bytes: Bytes48,
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z_bytes: Bytes32,
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y_bytes: Bytes32,
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proof_bytes: Bytes48) -> bool:
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"""
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Verify KZG proof that ``p(z) == y`` where ``p(z)`` is the polynomial represented by ``polynomial_kzg``.
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Receives inputs as bytes.
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Public method.
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"""
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assert len(commitment_bytes) == BYTES_PER_COMMITMENT
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assert len(z_bytes) == BYTES_PER_FIELD_ELEMENT
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assert len(y_bytes) == BYTES_PER_FIELD_ELEMENT
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assert len(proof_bytes) == BYTES_PER_PROOF
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return verify_kzg_proof_impl(bytes_to_kzg_commitment(commitment_bytes),
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bytes_to_bls_field(z_bytes),
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bytes_to_bls_field(y_bytes),
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bytes_to_kzg_proof(proof_bytes))
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```
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#### `verify_kzg_proof_impl`
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```python
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def verify_kzg_proof_impl(commitment: KZGCommitment,
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z: BLSFieldElement,
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y: BLSFieldElement,
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proof: KZGProof) -> bool:
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"""
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Verify KZG proof that ``p(z) == y`` where ``p(z)`` is the polynomial represented by ``polynomial_kzg``.
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"""
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# Verify: P - y = Q * (X - z)
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X_minus_z = bls.add(
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bls.bytes96_to_G2(KZG_SETUP_G2_MONOMIAL[1]),
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bls.multiply(bls.G2(), (BLS_MODULUS - z) % BLS_MODULUS),
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)
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P_minus_y = bls.add(bls.bytes48_to_G1(commitment), bls.multiply(bls.G1(), (BLS_MODULUS - y) % BLS_MODULUS))
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return bls.pairing_check([
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[P_minus_y, bls.neg(bls.G2())],
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[bls.bytes48_to_G1(proof), X_minus_z]
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])
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```
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#### `verify_kzg_proof_batch`
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```python
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def verify_kzg_proof_batch(commitments: Sequence[KZGCommitment],
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zs: Sequence[BLSFieldElement],
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ys: Sequence[BLSFieldElement],
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proofs: Sequence[KZGProof]) -> bool:
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"""
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Verify multiple KZG proofs efficiently.
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"""
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assert len(commitments) == len(zs) == len(ys) == len(proofs)
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# Compute a random challenge. Note that it does not have to be computed from a hash,
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# r just has to be random.
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degree_poly = int.to_bytes(FIELD_ELEMENTS_PER_BLOB, 8, KZG_ENDIANNESS)
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num_commitments = int.to_bytes(len(commitments), 8, KZG_ENDIANNESS)
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data = RANDOM_CHALLENGE_KZG_BATCH_DOMAIN + degree_poly + num_commitments
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# Append all inputs to the transcript before we hash
|
|
for commitment, z, y, proof in zip(commitments, zs, ys, proofs):
|
|
data += commitment \
|
|
+ int.to_bytes(z, BYTES_PER_FIELD_ELEMENT, KZG_ENDIANNESS) \
|
|
+ int.to_bytes(y, BYTES_PER_FIELD_ELEMENT, KZG_ENDIANNESS) \
|
|
+ proof
|
|
|
|
r = hash_to_bls_field(data)
|
|
r_powers = compute_powers(r, len(commitments))
|
|
|
|
# Verify: e(sum r^i proof_i, [s]) ==
|
|
# e(sum r^i (commitment_i - [y_i]) + sum r^i z_i proof_i, [1])
|
|
proof_lincomb = g1_lincomb(proofs, r_powers)
|
|
proof_z_lincomb = g1_lincomb(
|
|
proofs,
|
|
[BLSFieldElement((int(z) * int(r_power)) % BLS_MODULUS) for z, r_power in zip(zs, r_powers)],
|
|
)
|
|
C_minus_ys = [bls.add(bls.bytes48_to_G1(commitment), bls.multiply(bls.G1(), (BLS_MODULUS - y) % BLS_MODULUS))
|
|
for commitment, y in zip(commitments, ys)]
|
|
C_minus_y_as_KZGCommitments = [KZGCommitment(bls.G1_to_bytes48(x)) for x in C_minus_ys]
|
|
C_minus_y_lincomb = g1_lincomb(C_minus_y_as_KZGCommitments, r_powers)
|
|
|
|
return bls.pairing_check([
|
|
[bls.bytes48_to_G1(proof_lincomb), bls.neg(bls.bytes96_to_G2(KZG_SETUP_G2_MONOMIAL[1]))],
|
|
[bls.add(bls.bytes48_to_G1(C_minus_y_lincomb), bls.bytes48_to_G1(proof_z_lincomb)), bls.G2()]
|
|
])
|
|
```
|
|
|
|
#### `compute_kzg_proof`
|
|
|
|
```python
|
|
def compute_kzg_proof(blob: Blob, z_bytes: Bytes32) -> Tuple[KZGProof, Bytes32]:
|
|
"""
|
|
Compute KZG proof at point `z` for the polynomial represented by `blob`.
|
|
Do this by computing the quotient polynomial in evaluation form: q(x) = (p(x) - p(z)) / (x - z).
|
|
Public method.
|
|
"""
|
|
assert len(blob) == BYTES_PER_BLOB
|
|
assert len(z_bytes) == BYTES_PER_FIELD_ELEMENT
|
|
polynomial = blob_to_polynomial(blob)
|
|
proof, y = compute_kzg_proof_impl(polynomial, bytes_to_bls_field(z_bytes))
|
|
return proof, y.to_bytes(BYTES_PER_FIELD_ELEMENT, KZG_ENDIANNESS)
|
|
```
|
|
|
|
#### `compute_quotient_eval_within_domain`
|
|
|
|
```python
|
|
def compute_quotient_eval_within_domain(z: BLSFieldElement,
|
|
polynomial: Polynomial,
|
|
y: BLSFieldElement
|
|
) -> BLSFieldElement:
|
|
"""
|
|
Given `y == p(z)` for a polynomial `p(x)`, compute `q(z)`: the KZG quotient polynomial evaluated at `z` for the
|
|
special case where `z` is in roots of unity.
|
|
|
|
For more details, read https://dankradfeist.de/ethereum/2021/06/18/pcs-multiproofs.html section "Dividing
|
|
when one of the points is zero". The code below computes q(x_m) for the roots of unity special case.
|
|
"""
|
|
roots_of_unity_brp = bit_reversal_permutation(compute_roots_of_unity(FIELD_ELEMENTS_PER_BLOB))
|
|
result = 0
|
|
for i, omega_i in enumerate(roots_of_unity_brp):
|
|
if omega_i == z: # skip the evaluation point in the sum
|
|
continue
|
|
|
|
f_i = int(BLS_MODULUS) + int(polynomial[i]) - int(y) % BLS_MODULUS
|
|
numerator = f_i * int(omega_i) % BLS_MODULUS
|
|
denominator = int(z) * (int(BLS_MODULUS) + int(z) - int(omega_i)) % BLS_MODULUS
|
|
result += int(div(BLSFieldElement(numerator), BLSFieldElement(denominator)))
|
|
|
|
return BLSFieldElement(result % BLS_MODULUS)
|
|
```
|
|
|
|
#### `compute_kzg_proof_impl`
|
|
|
|
```python
|
|
def compute_kzg_proof_impl(polynomial: Polynomial, z: BLSFieldElement) -> Tuple[KZGProof, BLSFieldElement]:
|
|
"""
|
|
Helper function for `compute_kzg_proof()` and `compute_blob_kzg_proof()`.
|
|
"""
|
|
roots_of_unity_brp = bit_reversal_permutation(compute_roots_of_unity(FIELD_ELEMENTS_PER_BLOB))
|
|
|
|
# For all x_i, compute p(x_i) - p(z)
|
|
y = evaluate_polynomial_in_evaluation_form(polynomial, z)
|
|
polynomial_shifted = [BLSFieldElement((int(p) - int(y)) % BLS_MODULUS) for p in polynomial]
|
|
|
|
# For all x_i, compute (x_i - z)
|
|
denominator_poly = [BLSFieldElement((int(x) - int(z)) % BLS_MODULUS)
|
|
for x in roots_of_unity_brp]
|
|
|
|
# Compute the quotient polynomial directly in evaluation form
|
|
quotient_polynomial = [BLSFieldElement(0)] * FIELD_ELEMENTS_PER_BLOB
|
|
for i, (a, b) in enumerate(zip(polynomial_shifted, denominator_poly)):
|
|
if b == 0:
|
|
# The denominator is zero hence `z` is a root of unity: we must handle it as a special case
|
|
quotient_polynomial[i] = compute_quotient_eval_within_domain(roots_of_unity_brp[i], polynomial, y)
|
|
else:
|
|
# Compute: q(x_i) = (p(x_i) - p(z)) / (x_i - z).
|
|
quotient_polynomial[i] = div(a, b)
|
|
|
|
return KZGProof(g1_lincomb(bit_reversal_permutation(KZG_SETUP_G1_LAGRANGE), quotient_polynomial)), y
|
|
```
|
|
|
|
#### `compute_blob_kzg_proof`
|
|
|
|
```python
|
|
def compute_blob_kzg_proof(blob: Blob, commitment_bytes: Bytes48) -> KZGProof:
|
|
"""
|
|
Given a blob, return the KZG proof that is used to verify it against the commitment.
|
|
This method does not verify that the commitment is correct with respect to `blob`.
|
|
Public method.
|
|
"""
|
|
assert len(blob) == BYTES_PER_BLOB
|
|
assert len(commitment_bytes) == BYTES_PER_COMMITMENT
|
|
commitment = bytes_to_kzg_commitment(commitment_bytes)
|
|
polynomial = blob_to_polynomial(blob)
|
|
evaluation_challenge = compute_challenge(blob, commitment)
|
|
proof, _ = compute_kzg_proof_impl(polynomial, evaluation_challenge)
|
|
return proof
|
|
```
|
|
|
|
#### `verify_blob_kzg_proof`
|
|
|
|
```python
|
|
def verify_blob_kzg_proof(blob: Blob,
|
|
commitment_bytes: Bytes48,
|
|
proof_bytes: Bytes48) -> bool:
|
|
"""
|
|
Given a blob and a KZG proof, verify that the blob data corresponds to the provided commitment.
|
|
|
|
Public method.
|
|
"""
|
|
assert len(blob) == BYTES_PER_BLOB
|
|
assert len(commitment_bytes) == BYTES_PER_COMMITMENT
|
|
assert len(proof_bytes) == BYTES_PER_PROOF
|
|
|
|
commitment = bytes_to_kzg_commitment(commitment_bytes)
|
|
|
|
polynomial = blob_to_polynomial(blob)
|
|
evaluation_challenge = compute_challenge(blob, commitment)
|
|
|
|
# Evaluate polynomial at `evaluation_challenge`
|
|
y = evaluate_polynomial_in_evaluation_form(polynomial, evaluation_challenge)
|
|
|
|
# Verify proof
|
|
proof = bytes_to_kzg_proof(proof_bytes)
|
|
return verify_kzg_proof_impl(commitment, evaluation_challenge, y, proof)
|
|
```
|
|
|
|
#### `verify_blob_kzg_proof_batch`
|
|
|
|
```python
|
|
def verify_blob_kzg_proof_batch(blobs: Sequence[Blob],
|
|
commitments_bytes: Sequence[Bytes48],
|
|
proofs_bytes: Sequence[Bytes48]) -> bool:
|
|
"""
|
|
Given a list of blobs and blob KZG proofs, verify that they correspond to the provided commitments.
|
|
Will return True if there are zero blobs/commitments/proofs.
|
|
Public method.
|
|
"""
|
|
|
|
assert len(blobs) == len(commitments_bytes) == len(proofs_bytes)
|
|
|
|
commitments, evaluation_challenges, ys, proofs = [], [], [], []
|
|
for blob, commitment_bytes, proof_bytes in zip(blobs, commitments_bytes, proofs_bytes):
|
|
assert len(blob) == BYTES_PER_BLOB
|
|
assert len(commitment_bytes) == BYTES_PER_COMMITMENT
|
|
assert len(proof_bytes) == BYTES_PER_PROOF
|
|
commitment = bytes_to_kzg_commitment(commitment_bytes)
|
|
commitments.append(commitment)
|
|
polynomial = blob_to_polynomial(blob)
|
|
evaluation_challenge = compute_challenge(blob, commitment)
|
|
evaluation_challenges.append(evaluation_challenge)
|
|
ys.append(evaluate_polynomial_in_evaluation_form(polynomial, evaluation_challenge))
|
|
proofs.append(bytes_to_kzg_proof(proof_bytes))
|
|
|
|
return verify_kzg_proof_batch(commitments, evaluation_challenges, ys, proofs)
|
|
```
|