Light client

/**
 * Light client: verify a block filter against its header and coinbase commitment, test it
 * for our address, and verify the latest signed checkpoint.
 *
 *   ARREKTA_URL=http://127.0.0.1:28332 npx tsx examples/light-client.ts
 */
import {
  createClient,
  decodeAddress,
  fromHex,
  getBlock,
  getBlockFilter,
  getChain,
  getCheckpoints,
  getFilterHeaders,
  keychainFromSeed,
  matchFilter,
  networkSignerSet,
  verifyBlockFilterProof,
  verifyCheckpoint,
} from 'arrekta-sdk';
 
const URL = process.env.ARREKTA_URL ?? 'http://127.0.0.1:28332';
const SEED = fromHex(process.env.ARREKTA_SEED ?? 'a1'.repeat(32));
 
// 1. Connect and pick the tip.
const client = createClient({ url: URL });
const chain = await getChain(client);
const wallet = keychainFromSeed(SEED, { network: chain.network });
const height = chain.height;
 
// 2. Filter headers: the tip's header must chain from its parent's.
const { headers } = await getFilterHeaders(client, { start: Math.max(height - 1, 0), count: 2 });
const prevHeader = height > 0 ? headers[0]!.filter_header! : '00'.repeat(32);
 
// 3. Fetch the tip's filter and verify it (coinbase commitment, merkle branch, header).
const f = await getBlockFilter(client, { id: height });
const header = await getBlock(client, { id: height, txs: 'none' });
// the proof's merkle root must be the PoW-checked header's
const ok = header.merkle_root === f.merkle_root && verifyBlockFilterProof(f, prevHeader).ok;
console.log(`block ${height}: filter verified = ${ok}`);
 
// 4. Test the filter locally for our address (the node never learns what we watch).
const mine = matchFilter(f.prev_hash, f.filter, [decodeAddress(wallet.address(0), chain.network)]);
console.log(`block ${height} may pay ${wallet.address(0)}: ${mine}`);
 
// 5. Verify the latest signed checkpoint against the network's signer group.
const { latest } = await getCheckpoints(client);
const signers = networkSignerSet(chain.network);
if (latest && signers) {
  console.log(`checkpoint ${latest.height}: final = ${verifyCheckpoint(latest.hex, signers, chain.network).final}`);
} else {
  console.log('no checkpoint yet');
}

"""Light client: verify a block filter against its header and coinbase commitment, test it
for our address, and verify the latest signed checkpoint.
 
    ARREKTA_URL=http://127.0.0.1:28332 python examples/light_client.py
"""
 
import os
 
from arrekta_sdk import (
    Client,
    keychain_from_seed,
    match_filter,
    network_signer_set,
    verify_block_filter,
    verify_checkpoint,
)
 
URL = os.environ.get("ARREKTA_URL", "http://127.0.0.1:28332")
SEED = bytes.fromhex(os.environ.get("ARREKTA_SEED", "a1" * 32))
 
 
def main() -> None:
    # 1. Connect and pick the tip.
    client = Client(URL)
    chain = client.get_chain()
    wallet = keychain_from_seed(SEED, network=chain["network"])
    height = chain["height"]
 
    # 2. Filter headers: the tip's header must chain from its parent's.
    headers = client.get_filter_headers(max(height - 1, 0), 2)["headers"]
    prev_header = headers[0]["filter_header"] if height > 0 else "00" * 32
 
    # 3. Fetch the tip's filter and verify it (coinbase commitment, merkle branch, header).
    f = client.get_block_filter(height)
    header = client.get_block(height, "none")
    ok = verify_block_filter(f, header=header, prev_filter_header=prev_header)
    print(f"block {height}: filter verified = {ok}")
 
    # 4. Test the filter locally for our address (the node never learns what we watch).
    mine = match_filter(f["prev_hash"], f["filter"], [wallet.address(0)])
    print(f"block {height} may pay {wallet.address(0)}: {mine}")
 
    # 5. Verify the latest signed checkpoint against the network's signer group.
    latest = client.get_checkpoints()["latest"]
    signers = network_signer_set(chain["network"])
    if latest and signers:
        print(f"checkpoint {latest['height']}: final = {verify_checkpoint(latest['hex'], signers, chain['network'])}")
    else:
        print("no checkpoint yet")
 
 
if __name__ == "__main__":
    main()