Cross-chain
Telling one chain that a BAMFS root exists on another. Designed and tested, not shipped.
Not shipped. Nothing here runs in production. CrossChainRegistry is
deployed on Base Sepolia and covered by tests, but no bridge adapter has been
wired to a real bridge and nothing is deployed on Base. Treat this page as a
design record.
BAMFS is per-chain by default: a root CID — directory or single file — exists only on the chain where it was written. Two mechanisms are designed to tell other chains that a given root exists somewhere.
Proof of IPFS-CID parity
A root's canonical IPFS CID is derived on the source chain by
IpfsCidResolver. The same derivation is re-executed inside a zero-knowledge
guest, and the resulting proof is verified on the destination chain:
source chain destination chain
┌────────────────────┐ prover ┌───────────────────┐
│ IpfsCidResolver │ ──────────▶ │ IpfsCidVerifier │
│ computes IPFS CID │ proof │ └─ IZkVerifier │
└────────────────────┘ └───────────────────┘IpfsCidVerifier.verifyAndStore(rootCid, sourceChainId, ipfsCid, proof)
delegates to its verifier, then ABI-decodes the returned journal — the
public outputs the guest committed to — and asserts every field matches the
call arguments before recording anything. A host cannot forge any of the three
values without producing a journal that fails that decode.
See ZK proofs for the proving stack.
Bridge-authenticated existence claims
Where a canonical bridge already exists, CrossChainRegistry records
(cid, sourceChainId) on the destination chain on the authority of an
IBridgeAdapter. This trusts the bridge; the ZK path does not. It is the
cheaper option where that trust is already assumed.
Kind-agnostic by design
Both surfaces work identically for directory roots and single-file roots. The
guest dispatches on a tagged Directory | File input internally, but no kind
flag is recorded on the destination chain — (rootCid, sourceChainId) already
pins down exactly one kind, resolvable on the source chain through
DirectoryStore or FileStore.
The content layer is the authority on what a root is, whether or not a project token points at it.
What a destination chain does and does not learn
A verified record says: this root, on that chain, resolves to this IPFS CID.
It does not make the bytes readable on the destination chain. Nothing is mirrored. Resolving the content still means reading the source chain or fetching the IPFS CID from a node that holds it.