Cross-Chain Bridge Guide

Bridges move assets between blockchains. This guide covers how they work, which to use, and how to stay safe.

Why Bridges Exist

Each blockchain is an isolated system. Bridges connect them:

Ethereum ←──Bridge──→ Arbitrum
    ↕                      ↕
  Bridge                 Bridge
    ↕                      ↕
 Base    ←──Bridge──→  Polygon

Use cases:

• Move ETH from Ethereum to Arbitrum for cheaper DeFi
• Access protocols only available on specific chains
• Consolidate assets scattered across chains

Bridge Architectures

Type 1: Native Bridges (Official L2 Bridges)

Used by rollup L2s to move between L1 and L2.

Bridge	Route	Deposit Time	Withdrawal Time
Arbitrum Bridge	ETH ↔ Arbitrum	~10 min	7 days (fraud proof)
Optimism Bridge	ETH ↔ Optimism	~10 min	7 days (fraud proof)
Base Bridge	ETH ↔ Base	~10 min	7 days
zkSync Bridge	ETH ↔ zkSync	~10 min	~1 hour (ZK proof)

The 7-day problem: Optimistic rollups require a 7-day challenge period for withdrawals to L1. This is why third-party bridges exist.

Type 2: Liquidity Network Bridges

Pre-fund liquidity on both chains. Users swap locally:

User deposits ETH on Chain A → Receives ETH from liquidity pool on Chain B
(No actual cross-chain message needed — just liquidity matching)

Bridge	Speed	Chains	Best For
Stargate	1–5 min	15+	Stablecoins, large amounts
Across	2–10 min	10+	ETH, fast transfers
Hop	5–20 min	5+	ETH, stablecoins

Pros: Fast, no 7-day wait Cons: Limited by available liquidity, fees

Type 3: Message-Passing Bridges

Send a message cross-chain, mint/release on destination:

Bridge	Mechanism	Chains
Wormhole	Guardian network validates	30+
LayerZero	Oracle + relayer (ultralight)	30+
Axelar	PoS validator network	50+

Pros: Support many chains and token types Cons: Trust additional validator set, historically targeted by hackers

Type 4: Lock-and-Mint

1. Lock tokens on Chain A
2. Mint wrapped tokens on Chain B
3. To return: Burn on Chain B → Unlock on Chain A

Used by: Wormhole (wETH), Multichain (any-token), many protocol-specific bridges

Risk: If bridge contract is hacked, all locked tokens are at risk.

Bridge Comparison

Bridge	Speed	Cost	Security	Best For
Official L2 Bridge	10 min in / 7 days out	Gas only	Highest (L1 security)	Large amounts, no rush
Stargate	1–5 min	~$0.50–5	High (LayerZero)	Stablecoins
Across	2–10 min	~$0.50–3	High (UMA optimistic)	ETH, fast transfers
Hop	5–20 min	~$1–5	High (AMM model)	Proven, reliable
Wormhole	5–15 min	Variable	Medium (guardian set)	Multi-chain (Solana)
Synapse	5–15 min	~$1–5	Medium	Wide chain support

Security History

Bridges have been the #1 target for hacks in crypto:

Bridge	Date	Loss	What Happened
Ronin (Axie)	Mar 2022	$625M	Validator keys compromised
Wormhole	Feb 2022	$325M	Smart contract bug
Nomad	Aug 2022	$190M	Logic error in verification
Multichain	Jul 2023	$130M	Admin key compromise
Harmony	Jun 2022	$100M	Multisig key theft

Lesson: Bridges are high-value targets. Use established bridges with strong security track records.

Bridging to Arbitrum (Sperax's Home Chain)

To use Sperax (USDs, SPA staking, Farms), you need assets on Arbitrum:

Recommended Paths

From	Asset	Recommended Bridge	Time	Cost
Ethereum	ETH	Across or Stargate	2–5 min	~$1–3
Ethereum	USDC	Stargate	1–5 min	~$0.50–2
Ethereum	Any ERC-20	Arbitrum Official Bridge	10 min	Gas only
Base	ETH/USDC	Stargate or Across	2–5 min	~$0.50–2
Optimism	ETH/USDC	Stargate or Across	2–5 min	~$0.50–2
Polygon	USDC	Stargate	1–5 min	~$0.50

Step-by-Step: Bridge ETH to Arbitrum

1. Go to bridge.arbitrum.io (official) or across.to (faster)
2. Connect wallet
3. Select: From Ethereum → To Arbitrum
4. Enter ETH amount
5. Review fees and estimated time
6. Approve and send transaction
7. Wait for confirmation on Arbitrum
8. Verify on Arbiscan that funds arrived

Best Practices

Safety Checklist

• Use established bridges only — Stargate, Across, Hop, official L2 bridges
• Verify the URL — bookmark bridge sites, don't click links
• Start with a small test — bridge $10 first before large amounts
• Check bridge TVL — higher TVL = more battle-tested
• Verify on destination — confirm tokens arrived on the destination chain
• Understand wrapped vs native — bridged USDC might be different from native USDC

Common Mistakes

Mistake	How to Avoid
Bridging to wrong chain	Double-check destination chain before confirming
Not having gas on destination	Keep 0.001+ ETH on Arbitrum/L2 for gas
Using a hacked/deprecated bridge	Check if bridge is still active and maintained
Bridging during congestion	Check L1 gas prices if bridging via Ethereum
Getting wrapped tokens instead of native	Some bridges give wrapped USDC.e instead of native USDC

Native vs Wrapped Tokens

Term	Meaning	Example on Arbitrum
Native	Issued directly on the chain	USDC (Circle native)
Bridged/Wrapped	Bridged version of an L1 token	USDC.e (bridged from Ethereum)

Both are usable, but native is preferred for DeFi (better liquidity, no bridge risk).

Sperax accepts both: USDs can be minted with both USDC (native) and USDC.e (bridged) on Arbitrum.

Cost Optimization

Tips

1. Use L2-to-L2 bridges when possible (skip L1 entirely)
2. Bridge during low-gas periods (weekends, US nighttime)
3. Batch your bridging — one $1000 bridge is cheaper than ten $100 bridges
4. Compare on aggregators — Li.Fi, Bungee, and Socket aggregate multiple bridges

Bridge Cost Aggregators

Aggregator	What It Does
Li.Fi	Compares routes across bridges + DEXes
Bungee (Socket)	Multi-bridge route optimization
Jumper	Cross-chain swap + bridge in one tx

Agent Tips

1. Official L2 bridges are safest but slowest (7-day withdrawal)
2. Stargate for stablecoins, Across for ETH — best speed/security balance
3. Never use unknown bridges — bridge hacks are the largest losses in crypto
4. Always keep gas on destination — users forget they need ETH for gas on L2
5. Test with small amount first — especially on a new bridge or chain
6. For Sperax/Arbitrum users: Across or Stargate from Ethereum is the recommended path

Links

• Arbitrum Bridge: https://bridge.arbitrum.io
• Stargate: https://stargate.finance
• Across: https://across.to
• Hop Protocol: https://hop.exchange
• Li.Fi (aggregator): https://li.fi
• L2 Bridge Comparison: https://l2beat.com/bridges
• Sperax (on Arbitrum): https://app.sperax.io