How the Bitmark browser node works

A full Bitmark (BTM) node and wallet that run in a browser tab — no install, no server you have to trust for consensus. It's the bitcoin-kernel/browser-node stack pointed at a small, old, live coin. ← back to the node

The idea

The hard part of a node is consensus — deciding which blocks and transactions are valid. That logic is a single schema-driven engine (the "kernel"): it validates headers, blocks, scripts and ECDSA signatures, and maintains a UTXO set. A coin is just a set of parameters fed to that engine. Bitmark is one more parameter set — btm:mainnet: magic f9beb4d9, port 9265, P2PKH addresses (b…), 2-minute blocks. Same engine, live coin.

Getting bytes into the tab

A browser can't open raw TCP. So everything rides WebRTC:

browser tab ──WebRTC──▶ byte-pipe bridge ──TCP──▶ { Bitmark peer :9265 (blocks, headers, mempool, broadcast) ElectrumX server (address balances, fast wallet) } browser tab ◀──WebRTC──▶ browser tab (the mesh: block propagation, no server in the data path) WebTorrent swarm ──▶ browser tab (the assumeUTXO keystone — too big for a web host)

The bridges are pure transport — they relay raw bytes and can't forge a block or a balance the tab doesn't re-check. They rendezvous in rooms on a WebRTC signaling server (a JavaScript Solid Server pod).

The full node (follows the tip)

Re-validating ~2.4M blocks in a tab is impractical, so — exactly like Bitcoin Core's assumeUTXO — the node loads a UTXO snapshot at a recent height (a "keystone"), then validates forward to the tip and follows it:

Keystone — the UTXO set at the tip (~795k coins), exported from a synced node, distributed over WebTorrent (content-addressed: the swarm verifies every piece against the infohash). full node →
Catch up — fetch the few blocks since the keystone over P2P, fully validate each (structure, contextual rules, every signature) against the UTXO set with the kernel.
Follow — poll for new blocks, validate + apply, stay current.

The wallet

Keys are generated locally and never leave the tab (keys →). The wallet derives legacy P2PKH addresses (Bitmark has no SegWit), reads balance + UTXOs from your own node's validated UTXO set (the set fullnode persists to OPFS — no trusted index), selects coins, signs the legacy sighash with the bundled WASM secp, checks the tx against the node's own verifier, and broadcasts peer-to-peer over the bridge. ElectrumX remains a one-click fallback for balance and broadcast (electrum.html). You can also look up any address, watch the mempool for incoming payments, and prove a tx's inclusion with a merkle proof.

Honest corners

Multi-algo PoW. Bitmark blocks are mined with several algorithms; the block-identity hash is SHA256d (validated), but PoW difficulty is delegated, not re-checked — the chain's shape is validated, not its accumulated work.
Electrum for convenience. The wallet reads balances from a trusted ElectrumX index for speed; the full node is the trust-minimized path (its own UTXO set). Signing is always local.
One historical block carries a bad signature (an old Bitmark bug the network checkpointed past); the validators count it as a known anomaly rather than rejecting the chain.

Built on the bitcoin-kernel engine, unchanged — only the parameters differ. source