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Lattice

Bitcoin-anchored genesis

The Nexus genesis is pinned in source as NexusGenesis.expectedBlockHash (bafyreiggtg4ezifboyekbf4gxst2jr3mpjqcxsbmopy7w6fp46g4ngpgxa), and a node verifies that the genesis it builds matches that value at boot. On its own the pin is a trusted constant: the one link in the security model that proof-of-work does not cover. Anyone could publish a different “golden” genesis, and nothing in the protocol says which one is the real network.

To remove that trust, the genesis CID is committed to Bitcoin. It is the OP_RETURN payload of a confirmed Bitcoin transaction, so the claim “this CID is the Nexus genesis, and it existed by this time” rests on Bitcoin proof-of-work and can be checked without trusting this repository.

The anchor

Section titled “The anchor”
Bitcoin block 970053 — 000000000000000000005260ddc48a2e8421fff7cb681ca999db1b65d119fdfc
Transaction 7501f77602b581f605e6bc61c310b540e17324d3cc292c18985d8a3464d23236
OP_RETURN payload 01711220c699b84ca0a17608a09786bca7a4c76c7a602bc82c73f1fb78afe78dc699e6b8

The payload is the genesis CID’s raw bytes (01 = CIDv1, 71 = dag-cbor, 12 20 = sha2-256, then the 32-byte digest). It decodes to NexusGenesis.expectedBlockHash. The same facts are recorded in code in BitcoinGenesisAnchor, next to the genesis they commit.

Two earlier Bitcoin transactions, in blocks 954137 and 960894, commit earlier Nexus genesis values that were replaced before this one. They are not this network.

The genesis is fixed

Section titled “The genesis is fixed”

The committed CID is derived from the genesis spec, the premine owner, and the genesis timestamp. Changing any of them changes the CID and leaves this anchor pointing at nothing, so those parameters are fixed. There is no procedure for re-pinning the genesis.

Verifying the anchor

Section titled “Verifying the anchor”

Trust nothing in this repository. The recorded txid, the constants in BitcoinGenesisAnchor, and any test are all controlled by whoever ships the source, which is exactly the party this anchor is meant to check. A forged genesis would arrive with matching forged constants and green tests.

The verification happens outside this repo, against the live Bitcoin chain:

  1. Fetch the transaction independently by its txid from your own Bitcoin node, or cross-check several independent block explorers. Confirm it is mined in block 970053 and that the block is buried under substantial later proof-of-work.
  2. Decode its OP_RETURN output and confirm the pushed bytes are exactly 01711220c699…e6b8, i.e. the CID bafyreiggtg4ezifboyekbf4gxst2jr3mpjqcxsbmopy7w6fp46g4ngpgxa.
  3. Confirm that CID is the genesis you run: nexusGenesisCID from the node’s /health, which the node derives from the genesis spec at boot.

For full rigor without trusting an explorer’s “confirmed” flag, work from raw data you fetch yourself: check that the 80-byte block header meets Bitcoin proof-of-work and hashes to the block hash, that the transaction Merkle-proves into the header’s merkle root, and that the header extends the Bitcoin chain you already trust.

Source: lattice-node/docs/design/bitcoin-anchored-genesis.md at 9abd15b1bb05