# ZooBC Guide to the ProxCell Working Paper

> ProxCell is Roberto Capodieci's March 2026 working paper for a geo-federated mobile payment architecture. It is not a live payment network today.

Canonical HTML: https://zoobc.com/proxcell/

Official paper: https://proxcell.network/

## Primary answer

ProxCell proposes that an in-person payment can receive optimistic local confirmation before global settlement completes. Two nearby devices create a signed co-location attestation. A local geo-cell committee checks available state and reaches a signature threshold. Signed net totals then move upward through six geographic settlement layers.

The paper targets millisecond confirmation at Layer 5 for local payments backed by a guarantee deposit. This is a design target for optimistic local confirmation, not a measured production benchmark and not global finality.

## Six proposed mechanisms

1. Physical contact: two devices exchange a timestamped challenge and session nonce over NFC, Bluetooth Low Energy, or both, then sign the event.
2. Local optimistic confirmation: a nearby committee checks state and signs before world-scale settlement completes.
3. Hierarchical net settlement: ordinary local transaction records are deduplicated at the city-district boundary and upper layers receive signed net totals.
4. Geographic isolation: nested financial buckets are intended to bound the effect of a local failure.
5. Mobile edge participation: ordinary phones can operate as voluntary, non-continuous edge nodes, while upper layers may use dedicated infrastructure.
6. Location commitments: co-location events can be accumulated into a Merkle tree so the network receives a root commitment rather than exact coordinates.

## Geographic layers

- Layer 5, micro-cell: about 1 km, targeted millisecond local confirmation
- Layer 4, city district: about 10 km, seconds
- Layer 3, metropolitan region: about 100 km, minutes
- Layer 2, country: national, minutes
- Layer 1, continent: continental, hours
- Layer 0, global: worldwide, hours

Under a seven-continent deployment, the paper's pure net-settlement model reduces ordinary local activity to one signed net value per continent at Layer 0. This does not apply to every payment. A payment crossing geographic sub-trees is routed individually to the lowest common layer containing both parties.

## Relationship to ZooBC

The paper identifies ZooBC's transaction-chain and state-archive architecture as a direct ancestor of its implementation path. It also discusses snapshot bootstrapping for mobile nodes and a relationship to Proof of Participation. This is a proposed design relationship, not a deployed ProxCell integration or an available ZooBC transaction type.

## Open questions

- Committee size, signature thresholds, and message complexity
- Relay resistance and proximity-channel selection
- Collateral ratios and fraud-unwinding rules
- Low-density fallback and layer activation thresholds
- Mobile snapshot size and bootstrap time
- Privacy under metadata correlation
- Settlement intervals and regulatory deployment

## Source and verification

- [Official paper page](https://proxcell.network/)
- [Working Paper v0.1 PDF](https://proxcell.network/i/ProxCell_Protocol.pdf)
- [Published document verification](https://proxcell.network/verify.html)
- SHA-256: `2dd9ba6ccf376d86348407731677f24b122f0e9c67af4c1e5a91146fc1cae662`
- Author: Roberto Capodieci
- Date: March 2026
- Status: Working Paper, Confidential Draft
- Pages: 23

## ZooBC next steps

- [Read the ZooBC developer guide](https://zoobc.com/developer)
- [Read Proof of Participation](https://zoobc.com/pop)
- [Join the project](https://zoobc.com/join)