Investigative Approaches to Cross-Chain Bridge Tracing
How bridges complicate tracing, analyzing lock-and-mint mechanisms, and tracking funds across multiple blockchains.
The proliferation of alternative blockchains (Layer 1s and Layer 2s) created a demand for interoperability. Cross-chain bridges fulfill this demand, allowing users to move value from Ethereum to Solana, Avalanche, or Arbitrum.
For criminals, bridges are the ultimate laundering tool. For investigators, they represent severe breaks in the chain of custody.
How Bridges Work (Lock and Mint)
Blockchains cannot natively communicate. Most bridges operate on a "lock and mint" model:
- •A user locks 10 ETH in a smart contract on Ethereum.
- •A centralized relayer or decentralized network of validators verifies the lock.
- •The bridge mints 10 Wrapped ETH (wETH) on the destination chain (e.g., Avalanche) and sends it to the user's specified address.
The Tracing Disconnect
When funds enter a bridge, the on-chain trail ends. A standard block explorer will only show the funds going into the bridge contract. It will not tell you where they emerged on the other side.
To continue the trace, investigators must correlate data across entirely different ledger systems.
Heuristics for Bridge Hopping
Finding the destination address requires analyzing specific parameters:
1. Address Reuse: Many users (and lazy criminals) use the same private key for EVM-compatible chains. If they bridge from Ethereum to Polygon, the destination address is often identical to the sending address.
2. Time and Amount Correlation: If 500 USDC goes into an Arbitrum bridge on Ethereum at 12:00 PM, investigators must scan the Arbitrum blockchain for 500 USDC emerging from the bridge contract shortly after 12:00 PM.
3. Event Logs: Advanced bridges emit transaction logs containing the encoded destination address. Skilled investigators can decode these logs to find the exact off-ramp without relying on guesswork.
Liquidity Pools and Native Swaps
More complex protocols like THORChain facilitate native cross-chain swaps (e.g., real BTC for real ETH) without wrapped tokens, utilizing massive decentralized liquidity pools. Tracing through these requires deep protocol-specific knowledge and continuous monitoring of the pool states.
Unbreakable Cross-Chain Tracking
Aletheia automatically decodes bridge logs and correlates liquidity pool data, seamlessly projecting your trace across dozens of blockchains without losing the thread.