Cross-chain bridge
A protocol that moves value or messages between two blockchains. TON has active bridges for USDT, ETH, BTC, jetton wrappers, and mini-app messaging.
Aliases: bridge, cross-chain bridge protocol
Cross-chain bridge is the protocol that moves value or arbitrary messages between two independent blockchains. Without a bridge, an asset on Ethereum cannot “appear” on TON — the chains have no native knowledge of one another.
Base mechanic: lock-and-mint
The dominant pattern:
- The user locks X USDT on Ethereum in a bridge contract.
- Bridge operators (or a ZK prover, or a multisig) verify the lock.
- On the TON side, a counterpart contract mints a wrapped USDT (in this case, the native USDT jetton).
- On the reverse trip the jetton is burned on TON and the original USDT is released on Ethereum.
An alternative is HTLC-based atomic swap — works for direct 1:1 exchanges but not for issuance-bridged assets.
Trust models
- Federated / multisig. A small validator set (5–20 keys) attests to events. Simple but trust-heavy.
- Light-client bridge. Contract on chain B runs a light client of chain A and verifies proofs. Higher gas, much safer.
- Optimistic / fraud-proof. A message is accepted if not challenged within a window.
- ZK-bridge. Cryptographic proofs of events. Strongest model, technically demanding.
Major TON bridges
- Toncoin — Ethereum / BNB. Two-way bridge from TON Foundation; TON travels as wTON / pTON on other chains.
- USDT. Native USDT exists on TON as a jetton, but bridges still move USDT between TON and other chains.
- NOT, DOGS and others. Some mini-app tokens have wrappers on other chains via third-party bridges.
Risk
Bridges are statistically the most exploited class of DeFi infrastructure. Chainalysis data shows bridges account for a major share of all crypto hack losses. Ronin, Wormhole, Nomad, Multichain — each individual incident exceeded hundreds of millions of dollars.
When you use a bridge:
- You are trusting not only the contract audit but the signers / prover / incentive design.
- A wrapped asset on chain B is the bridge’s IOU, not the “real” original asset.
- If the bridge collapses, the wrapped asset can go to zero even if the original on chain A is healthy.
For one-shot transfers of significant size, prefer a ZK-secured bridge or the most conservative federated bridge with a clean track record.