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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,200 @@ | ||
| // Importing directly from 'c-kzg' does not work, ignoring import/no-named-as-default-member err: | ||
| import cKzg from 'c-kzg'; | ||
| import type { Blob as BlobBuffer } from 'c-kzg'; | ||
|
|
||
| import { poseidon2Hash, sha256 } from '../crypto/index.js'; | ||
| import { Fr } from '../fields/index.js'; | ||
| import { BufferReader, serializeToBuffer } from '../serialize/index.js'; | ||
| import { deserializeEncodedBlobFields } from './encoding.js'; | ||
|
|
||
| /* eslint-disable import/no-named-as-default-member */ | ||
| const { BYTES_PER_BLOB, FIELD_ELEMENTS_PER_BLOB, blobToKzgCommitment, computeKzgProof, verifyKzgProof } = cKzg; | ||
|
|
||
| // The prefix to the EVM blobHash, defined here: https://eips.ethereum.org/EIPS/eip-4844#specification | ||
| export const VERSIONED_HASH_VERSION_KZG = 0x01; | ||
|
|
||
| /** | ||
| * A class to create, manage, and prove EVM blobs. | ||
| */ | ||
| export class Blob { | ||
| constructor( | ||
| /** The blob to be broadcast on L1 in bytes form. */ | ||
| public readonly data: BlobBuffer, | ||
| /** The hash of all tx effects inside the blob. Used in generating the challenge z and proving that we have included all required effects. */ | ||
| public readonly fieldsHash: Fr, | ||
| /** Challenge point z (= H(H(tx_effects), kzgCommmitment). Used such that p(z) = y. */ | ||
| public readonly challengeZ: Fr, | ||
| /** Evaluation y = p(z), where p() is the blob polynomial. BLS12 field element, rep. as BigNum in nr, bigint in ts. */ | ||
| public readonly evaluationY: Buffer, | ||
| /** Commitment to the blob C. Used in compressed BLS12 point format (48 bytes). */ | ||
| public readonly commitment: Buffer, | ||
| /** KZG opening proof for y = p(z). The commitment to quotient polynomial Q, used in compressed BLS12 point format (48 bytes). */ | ||
| public readonly proof: Buffer, | ||
| ) {} | ||
|
|
||
| static fromEncodedBlobBuffer(blob: BlobBuffer, multiBlobFieldsHash?: Fr): Blob { | ||
| const fields: Fr[] = deserializeEncodedBlobFields(blob); | ||
| return Blob.fromFields(fields, multiBlobFieldsHash); | ||
| } | ||
|
|
||
| static fromFields(fields: Fr[], multiBlobFieldsHash?: Fr): Blob { | ||
| if (fields.length > FIELD_ELEMENTS_PER_BLOB) { | ||
| throw new Error( | ||
| `Attempted to overfill blob with ${fields.length} elements. The maximum is ${FIELD_ELEMENTS_PER_BLOB}`, | ||
| ); | ||
| } | ||
|
|
||
| const data = Buffer.concat([serializeToBuffer(fields)], BYTES_PER_BLOB); | ||
|
|
||
| // This matches the output of SpongeBlob.squeeze() in the blob circuit | ||
| const fieldsHash = multiBlobFieldsHash ? multiBlobFieldsHash : poseidon2Hash(fields); | ||
| const commitment = Buffer.from(blobToKzgCommitment(data)); | ||
| const challengeZ = poseidon2Hash([fieldsHash, ...commitmentToFields(commitment)]); | ||
| const res = computeKzgProof(data, challengeZ.toBuffer()); | ||
| if (!verifyKzgProof(commitment, challengeZ.toBuffer(), res[1], res[0])) { | ||
| throw new Error(`KZG proof did not verify.`); | ||
| } | ||
| const proof = Buffer.from(res[0]); | ||
| const evaluationY = Buffer.from(res[1]); | ||
|
|
||
| return new Blob(data, fieldsHash, challengeZ, evaluationY, commitment, proof); | ||
| } | ||
|
|
||
| // TODO: add unit test | ||
| static fromJson(json: { blob: string; kzg_commitment: string; kzg_proof: string }): Blob { | ||
| const blobBuffer = Buffer.from(json.blob.slice(2), 'hex'); | ||
|
|
||
| const blob = Blob.fromEncodedBlobBuffer(blobBuffer); | ||
|
|
||
| if (blob.commitment.toString('hex') !== json.kzg_commitment.slice(2)) { | ||
| throw new Error('KZG commitment does not match'); | ||
| } | ||
|
|
||
| return blob; | ||
| } | ||
|
|
||
| // TODO: think if naming should change for encoded / non encoded blob payloads | ||
| toFields(): Fr[] { | ||
| return deserializeEncodedBlobFields(this.data); | ||
| } | ||
|
|
||
| toEncodedFields(): Fr[] { | ||
| return deserializeEncodedBlobFields(this.data); | ||
| } | ||
|
|
||
| // 48 bytes encoded in fields as [Fr, Fr] = [0->31, 31->48] | ||
| commitmentToFields(): [Fr, Fr] { | ||
| return commitmentToFields(this.commitment); | ||
| } | ||
|
|
||
| // Returns ethereum's versioned blob hash, following kzg_to_versioned_hash: https://eips.ethereum.org/EIPS/eip-4844#helpers | ||
| getEthVersionedBlobHash(): Buffer { | ||
| const hash = sha256(this.commitment); | ||
| hash[0] = VERSIONED_HASH_VERSION_KZG; | ||
| return hash; | ||
| } | ||
|
|
||
| static getEthVersionedBlobHash(commitment: Buffer): Buffer { | ||
| const hash = sha256(commitment); | ||
| hash[0] = VERSIONED_HASH_VERSION_KZG; | ||
| return hash; | ||
| } | ||
|
|
||
| toBuffer(): Buffer { | ||
| return Buffer.from( | ||
| serializeToBuffer( | ||
| this.data.length, | ||
| this.data, | ||
| this.fieldsHash, | ||
| this.challengeZ, | ||
| this.evaluationY.length, | ||
| this.evaluationY, | ||
| this.commitment.length, | ||
| this.commitment, | ||
| this.proof.length, | ||
| this.proof, | ||
| ), | ||
| ); | ||
| } | ||
|
|
||
| static fromBuffer(buf: Buffer | BufferReader): Blob { | ||
| const reader = BufferReader.asReader(buf); | ||
| return new Blob( | ||
| reader.readUint8Array(), | ||
| reader.readObject(Fr), | ||
| reader.readObject(Fr), | ||
| reader.readBuffer(), | ||
| reader.readBuffer(), | ||
| reader.readBuffer(), | ||
| ); | ||
| } | ||
|
|
||
| /** | ||
| * Get the size of the blob in bytes | ||
| */ | ||
| getSize() { | ||
| return this.data.length; | ||
| } | ||
|
|
||
| // Returns a proof of opening of the blob to verify on L1 using the point evaluation precompile: | ||
| // * input[:32] - versioned_hash | ||
| // * input[32:64] - z | ||
| // * input[64:96] - y | ||
| // * input[96:144] - commitment C | ||
| // * input[144:192] - proof (a commitment to the quotient polynomial q(X)) | ||
| // See https://eips.ethereum.org/EIPS/eip-4844#point-evaluation-precompile | ||
| getEthBlobEvaluationInputs(): `0x${string}` { | ||
| const buf = Buffer.concat([ | ||
| this.getEthVersionedBlobHash(), | ||
| this.challengeZ.toBuffer(), | ||
| this.evaluationY, | ||
| this.commitment, | ||
| this.proof, | ||
| ]); | ||
| return `0x${buf.toString('hex')}`; | ||
| } | ||
|
|
||
| static getEthBlobEvaluationInputs(blobs: Blob[]): `0x${string}` { | ||
| let buf = Buffer.alloc(0); | ||
| blobs.forEach(blob => { | ||
| buf = Buffer.concat([ | ||
| buf, | ||
| blob.getEthVersionedBlobHash(), | ||
| blob.challengeZ.toBuffer(), | ||
| blob.evaluationY, | ||
| blob.commitment, | ||
| blob.proof, | ||
| ]); | ||
| }); | ||
| // For multiple blobs, we prefix the number of blobs: | ||
| const lenBuf = Buffer.alloc(1); | ||
| lenBuf.writeUint8(blobs.length); | ||
| buf = Buffer.concat([lenBuf, buf]); | ||
| return `0x${buf.toString('hex')}`; | ||
| } | ||
|
|
||
| static getViemKzgInstance() { | ||
| return { | ||
| blobToKzgCommitment: cKzg.blobToKzgCommitment, | ||
| computeBlobKzgProof: cKzg.computeBlobKzgProof, | ||
| }; | ||
| } | ||
|
|
||
| // Returns as many blobs as we require to broadcast the given fields | ||
| // Assumes we share the fields hash between all blobs | ||
| static getBlobs(fields: Fr[]): Blob[] { | ||
| const numBlobs = Math.max(Math.ceil(fields.length / FIELD_ELEMENTS_PER_BLOB), 1); | ||
| const multiBlobFieldsHash = poseidon2Hash(fields); | ||
| const res = []; | ||
| for (let i = 0; i < numBlobs; i++) { | ||
| const end = fields.length < (i + 1) * FIELD_ELEMENTS_PER_BLOB ? fields.length : (i + 1) * FIELD_ELEMENTS_PER_BLOB; | ||
| res.push(Blob.fromFields(fields.slice(i * FIELD_ELEMENTS_PER_BLOB, end), multiBlobFieldsHash)); | ||
| } | ||
| return res; | ||
| } | ||
| } | ||
|
|
||
| // 48 bytes encoded in fields as [Fr, Fr] = [0->31, 31->48] | ||
| function commitmentToFields(commitment: Buffer): [Fr, Fr] { | ||
| return [new Fr(commitment.subarray(0, 31)), new Fr(commitment.subarray(31, 48))]; | ||
| } |
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