> ## Documentation Index
> Fetch the complete documentation index at: https://docs.binibit.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Bridges

> Two bridges: Bridge A (CRS↔USBI) and Bridge B (BINI off-chain↔native), plus future Ethereum cross-chain bridge.

## Three bridges total

| Bridge                 | What it moves                | Direction                    | Ratio      | Level gate      |
| ---------------------- | ---------------------------- | ---------------------------- | ---------- | --------------- |
| **Bridge A**           | Crystals (CRS) ↔ USBI        | Off-chain ↔ BiniChain ERC-20 | 10,000 : 1 | Level 5         |
| **Bridge B**           | BINI off-chain ↔ BINI native | Off-chain ↔ BiniChain native | 1 : 1      | Level 7         |
| **Cross-chain bridge** | ERC-20 BINI ↔ native BINI    | Ethereum ↔ BiniChain         | 1 : 1      | None (standard) |

Bridge A and B are off-chain ↔ on-chain (within the Binibit ecosystem). The cross-chain bridge connects BiniChain to Ethereum.

## Bridge A — CRS to USBI

Detail: [Tokenomics → USBI Bridge](/tokenomics/usbi-bridge), [Bini App → USBI Bridge](/bini-app/usbi-bridge).

Summary:

* Convert off-chain Crystals (CRS) earned in Bini App into on-chain USBI ERC-20
* Fixed rate: 10,000 CRS = 1 USBI
* Gated at Level 5 (50M XP)
* USBI used in BaiDEX pools as LP

The Bridge A contract on BiniChain mints USBI when off-chain CRS is consumed. The Bini App backend signs the redemption request; the contract verifies and mints.

## Bridge B — BINI off-chain to native

Detail: [Tokenomics → BINI Bridge](/tokenomics/bini-bridge), [Bini App → BINI Bridge](/bini-app/bini-bridge).

Summary:

* Convert off-chain BINI rewards (quest wins, lottery, grants) into native BINI on BiniChain
* Fixed 1:1 ratio
* Gated at Level 7 (105M XP)
* Native BINI used for gas, staking (after withdrawal to Ethereum), pool participation

The Bridge B contract on BiniChain transfers native BINI from the Rewards pool reserve when off-chain BINI is consumed. The Bini App backend signs; the contract verifies and transfers.

## Cross-chain bridge — Ethereum ↔ BiniChain

For users moving BINI between Ethereum (ERC-20) and BiniChain (native):

```
ERC-20 BINI on Ethereum  ←→  Native BINI on BiniChain  (1:1)
```

Mechanism (TBD pending team finalization):

* **Lock-and-mint**: lock BINI on origin chain, mint on destination
* **Burn-and-mint**: burn on origin, mint on destination (more capital-efficient but trusts the bridge contracts)

The exact mechanism + bridge contract addresses publish before mainnet. For now, the canonical path for cross-chain users is via Binibit Exchange (which handles the bridge as part of withdrawals).

## Anti-sybil

Bridges B and A both have anti-sybil designs:

| Bridge                     | Anti-sybil mechanism                                                 |
| -------------------------- | -------------------------------------------------------------------- |
| Bridge A (CRS→USBI)        | Level 5 gate + USBI entitlement cap (max 101K USBI per user)         |
| Bridge B (BINI off→native) | Level 7 gate + monthly cap (TBD value) + per-account fraud detection |
| Cross-chain                | Standard signature verification + nonce + replay protection          |

The L7 gate on Bridge B is intentionally high — BINI is real-value, so the gate has to filter out farm accounts.

## Bridge security

All bridges are smart contracts with:

* Audited code (audit firm TBD pre-mainnet)
* Multi-sig admin (no single key controls minting/locking)
* Emergency pause (can halt withdrawals if exploit detected)
* Time-delayed governance for parameter changes
* On-chain logs for every action

The bridge contracts custody real BINI (in the lock-and-mint case). Bridge security is **the most critical security concern** in the ecosystem.

## Failure modes

| Scenario                                 | What happens                                                                                  |
| ---------------------------------------- | --------------------------------------------------------------------------------------------- |
| Bridge contract has a bug                | Emergency pause; users wait for fix; no funds lost from contract                              |
| Bridge admin keys compromised            | Multi-sig requires multiple keys; mitigates single-key compromise                             |
| Cross-chain message lost                 | Replay protection ensures no double-spend; users can retry                                    |
| Off-chain backend (Bini App) compromised | Bridge contract verifies signatures cryptographically — backend can't mint without valid sigs |

## Related

<CardGroup cols={2}>
  <Card title="USBI Bridge (Tokenomics)" icon="bridge" href="/tokenomics/usbi-bridge">
    Bridge A formula
  </Card>

  <Card title="BINI Bridge (Tokenomics)" icon="bridge" href="/tokenomics/bini-bridge">
    Bridge B formula
  </Card>

  <Card title="Bini App / Bridges" icon="mobile" href="/bini-app/usbi-bridge">
    User-facing bridge UX
  </Card>

  <Card title="BINI Token" icon="coins" href="/bini-token/overview">
    What native BINI is for
  </Card>
</CardGroup>