Atomic Schlep: 멈출 수 없는 스와프의 아키텍처

Source: Dev.to

Introduction

Cross‑chain bridges have lost over $2 billion to hacks in recent years. A better way has been hiding in plain sight: atomic swaps. This deep dive explores why Hashed Timelock Contracts (HTLCs) and Scriptless Scripts represent the only truly trustless path for moving value between blockchains, and why the “schlep” of complexity is actually a feature, not a bug.

The Counterparty Problem

Throughout human commerce, the core challenge has been the counterparty risk: the moment one asset leaves one hand while the other has not yet arrived. Trust is required in that split second, and trust has repeatedly proven to be a security hole.

For millennia, societies introduced a third party—the village elder, escrow agent, clearinghouse, or bank—to bridge this gap. While this enabled trade to scale, it also centralized power, creating points of failure, rent‑seeking gatekeepers, and surveillance mechanisms.

The internet succeeded in disintermediating information (email, video publishing) but stalled in the realm of value. For two decades, online commerce was essentially traditional banking with a web interface: Alice and Bob still needed a middleman.

From Islands to Bridges

Bitcoin introduced peer‑to‑peer value transfer without a trusted intermediary, but it existed as an isolated island. Subsequent chains (Ethereum, Litecoin, Monero, etc.) created additional islands, reviving the counterparty problem: How does one move value between islands?

The industry’s obvious solution was to recreate the bank as “bridges.” These massive, often centralized or semi‑centralized vaults lock assets on one chain and issue IOUs on another, effectively rebuilding the structures blockchain was meant to dismantle.

Why Bridges Are Problematic

A typical bridge operates on a Lock‑and‑Mint model:

1. Lock – The user sends assets (e.g., Bitcoin) to an address controlled by the bridge.
2. Mint – After confirmation, the bridge’s smart contract on the destination chain mints a wrapped token (e.g., wBTC) and sends it to the user.

The wrapped token is merely a claim check; its value depends entirely on the security of the locked assets. This creates a honeypot for attackers: the larger the pooled assets, the more attractive the target.

Bridge Hacks Statistics

📊 Stat Alert (2022): Bridge hacks accounted for 69 % of all stolen crypto funds, totaling over $2 billion.

Notable Bridge Hacks

Ronin Bridge Hack

• Context: Ronin Network’s bridge supported the Axie Infinity game.
• Security Model: Multi‑signature with nine validators; five signatures required for withdrawals.
• Outcome: Attackers compromised five validator keys and drained $625 million in USDC and Ethereum, leaving wrapped assets worthless.

Wormhole Bridge Hack

• Context: Wormhole bridge between Solana and Ethereum.
• Vulnerability: A bug allowed the attacker to trick the bridge into minting Wrapped ETH without an actual deposit.
• Outcome: Approximately $320 million was stolen.

These incidents illustrate that pooling assets creates single points of failure. Even with robust code and multi‑sig setups, bridges remain vulnerable.

Privacy Concerns

Beyond security, bridges act as surveillance machines. Every interaction leaves a permanent, immutable trail linking addresses across chains, eroding privacy—a core principle of decentralized finance.

HTLCs and Scriptless Scripts: The Trustless Alternative

Hashed Timelock Contracts (HTLC)

An HTLC is a mechanism, not a bank. It enables Alice and Bob to trade directly, peer‑to‑peer, without trusting each other or any third party. The contract locks funds on both chains with two conditions:

1. Hashlock: The receiver must present a pre‑image of a known hash to claim the funds.
2. Timelock: If the pre‑image is not provided within a specified time, the sender can reclaim the funds.

This creates a cryptographic escrow that is enforceable on both chains without any custodial entity.

Scriptless Scripts

Scriptless Scripts extend HTLCs by embedding the contract logic within signatures (e.g., Schnorr signatures), preserving privacy while retaining trustlessness. They eliminate on‑chain script footprints, making atomic swaps censorship‑resistant and privacy‑preserving.

Conclusion

While custodial bridges dominate today due to ease of use, they introduce centralized risk, privacy loss, and single points of failure. The HTLC and its evolution, Scriptless Scripts, remain the only architecture that upholds the fundamental properties of crypto:

• Trustlessness – No reliance on third‑party custodians.
• Censorship resistance – Operations are enforced by consensus, not by any authority.
• Privacy – Minimal on‑chain data, especially with Scriptless Scripts.

Embracing the “schlep” of atomic swap complexity is essential for a truly decentralized, secure, and private cross‑chain future.