urkel

const bcrypto = require('bcrypto'); const urkel = require('urkel'); const {BLAKE2b, randomBytes} = bcrypto; const {Tree, Proof} = urkel; async function runUrkelExample() { // Create a tree using blake2b-256 with a 256-bit key size. // Specify a unique prefix path for the database files. const tree = new Tree({ hash: BLAKE2b, bits: 256, prefix: './urkel-db-example' }); await tree.open(); let keyToProve; // Transactions allow atomic operations on the tree. const txn = tree.transaction(); // Insert 500 random key-value pairs. for (let i = 0; i < 500; i++) { const k = randomBytes(32); // 32 bytes for 256 bits const v = randomBytes(300); await txn.insert(k, v); if (i === 250) keyToProve = k; // Save one key for proof } // Commit the transaction and retrieve the new root hash. const root = await txn.commit(); const snapshot = tree.snapshot(root); // Generate a cryptographic proof for the saved key. const proof = await snapshot.prove(keyToProve); // Verify the generated proof against the root, key, hash, and bits. const [code, value] = proof.verify(root, keyToProve, BLAKE2b, 256); if (code !== 0) { console.log('Could not verify proof: %s.', Proof.code(code)); } else if (value) { console.log('Valid proof for %s, value: %s', keyToProve.toString('hex'), value.toString('hex')); } else { console.log('Absence proof for %s.', keyToProve.toString('hex')); } // Close the tree when done to release file handles. await tree.close(); } runUrkelExample().catch(console.error);