Create and Validate a Block

Create one ALX Block from JSON content and validate both deterministic identities. A successful validation confirms that the content and declared parent set produce the recorded contentHash and blockHash.

Before You Start

Use Node.js 20 or later and the published @alx-protocol/sdk package. No account, API key, network connection, smart contract, blockchain, or production data is required.

Workflow

1. Create a Block from JSON content and an empty parent set.
2. Inspect the generated contentHash and blockHash.
3. Run validateBlock() to recompute and compare both deterministic identities.
4. Modify the content, contentHash, blockHash, or parent set.
5. Run validateBlock() again and confirm that validation fails.

What Validation Confirms

validateBlock() performs local Block validation.

A successful result confirms that:

• contentHash matches the canonicalized content.
• blockHash matches the canonicalized content and normalized parent set.
• The Block satisfies protocol validation requirements.

Validation uses only protocol data. Any conforming implementation produces equivalent validation results from equivalent protocol inputs.

Prerequisites

Use Node.js 20 or later and install the package from npm.

Install the package:

npm i @alx-protocol/sdk

Dependency installation may require package-registry access. After installation, Block creation and validation run locally without credentials or a network connection.

Example

Create a root Block, validate both deterministic identities, and fail the process if validation does not pass.

Create validate-block.mjs:

import {
  createBlock,
  validateBlock,
} from '@alx-protocol/sdk';

const content = {type: 'example', value: 1};
const block = createBlock(content, []);
const result = validateBlock(block);

console.log(JSON.stringify({
  contentHash: result.contentHash,
  blockHash: result.blockHash,
  ok: result.ok,
}, null, 2));

if (!result.ok) process.exitCode = 1;

Run:

node validate-block.mjs

Output

The overall result is true only when both deterministic identity checks pass.

• contentHash.stored and contentHash.recomputed contain the same lowercase 0x-prefixed 32-byte hash.
• blockHash.stored and blockHash.recomputed contain the same lowercase 0x-prefixed 32-byte hash.
• Both match values and ok are true.
• The empty parent array makes the result a root Block.

Failure Cases

Change one protocol input at a time and inspect which deterministic identity fails.

Change	contentHash.match	blockHash.match	ok
Modify content	false	false	false
Modify stored contentHash only	false	true	false
Modify the parent set	true	false	false
Modify stored blockHash only	true	false	false

Malformed hashes are rejected before comparison. Reordering the same valid parents does not change identity because ALX normalizes the parent set.

Related Documentation

Continue with the protocol rules for Block structure, Block identity, canonicalization, and validation.

• Block
• Block Identity
• Canonicalization
• Verification