Модель UTXO в Биткоине: почему решения второго уровня BTC продолжают ошибаться

For years, the BTC L2 debate has been stuck in Ethereum’s shadow. Most L2s just copy EVM rollups—fast to build, but they strip away Bitcoin’s security guarantees and force users to juggle between BTC and EVM wallets. Not exactly smooth.

But here’s the thing: Bitcoin’s UTXO model is fundamentally different from Ethereum’s account-based system, and that difference matters way more than most people realize.

UTXO vs Account Model: Cash vs Bank Statement

Think of it this way:

• Account Model (Ethereum): Like your bank account. You have a total balance, and transactions just update that number.
• UTXO Model (Bitcoin): Like physical cash. Each coin you receive is a separate “bill” in your wallet. When you spend, you consume old bills and create new ones.

Example: You have a 1,000 yuan bill and buy something for 600 yuan.

• Account model: Your balance just becomes 400.
• UTXO model: You hand over the 1,000 yuan bill and get back a 400 yuan bill + the merchant gets a 600 yuan bill.

Each transaction literally destroys old UTXOs and creates new ones.

Enter eUTXO: UTXO on Steroids

Cardano and Ergo went further with Extended UTXO (eUTXO)—UTXOs that don’t just carry value, but also data and smart contract logic. Now each transaction isn’t just a payment; it’s a mini-smart contract that can enforce conditions.

Sounds powerful. But Bitcoin’s core UTXO model can’t do this natively.

The BRC-20 Problem: Running Windows on a Mac

BRC-20 tried to create tokens on Bitcoin using a clever hack: embed account-model data (in JSON format) into Bitcoin’s transaction scripts. Basically, they’re grafting Ethereum’s model onto Bitcoin’s UTXO system.

The problem? Bitcoin doesn’t understand this data. It’s like writing notes on physical cash—the bank doesn’t care what you scribbled.

To track BRC-20 token balances, projects need off-chain indexers—centralized servers that keep their own ledgers. That defeats the whole point of blockchain’s decentralization.

Newer protocols like ARC-20 and Runes tried to fix this by making tokens = satoshis (Bitcoin’s smallest unit). But Bitcoin’s 546 satoshi minimum output limit kills liquidity. You can’t split tokens finely enough for real trading.

Tech purists call BRC-20 a “technical regression.” And they’re not entirely wrong.

RGB Protocol: The Real Solution?

RGB was designed as a smart contract system for UTXO blockchains. The core idea: “Isomorphic binding”—map Bitcoin’s UTXOs to Nervos CKB’s “Cells” (an enhanced UTXO format that can handle smart contracts).

But RGB is still incomplete (v0.11 not even released yet), and full implementation may never happen.

CKB’s RGB++ Bet: Cross-Chain Without Bridges

This is where it gets interesting. CKB’s RGB++ protocol essentially says:

“Stop trying to lock BTC into L2. Instead, validate transactions on both Bitcoin and CKB simultaneously. Use CKB for complex smart contracts, Bitcoin for the base layer security.”

How it works:

• Assets issued on Bitcoin L1
• Smart contract functionality happens on CKB L2 (using eUTXO-style Cells)
• No bridge needed—just dual-chain verification
• Users don’t need special clients or store transaction history locally

It’s “intentional cross-chain” instead of “asset cross-chain”—you’re moving execution, not locking coins.

The Bet

RGB++ is still conceptual and unproven. But it represents a fundamentally different approach: instead of forcing Bitcoin into Ethereum-style L2s, work with Bitcoin’s UTXO design, not against it.

Whether it actually ships and scales is another question. But as a direction? It’s worth watching.