Cross-chain technology allows encrypted assets to flow freely between different blockchains, making it a necessity in the multi-chain world.

However, the blockchain world has long suffered from the pain of cross-chain bridges. On the one hand, this is because mainstream cross-chain bridges on the market often use multi-signature methods, requiring a high level of trust assumption. Trusting that the multi-signature parties of the cross-chain bridge will not act maliciously or embezzle funds. Cross-chain solutions with relatively weak trust assumptions have not been widely adopted due to poor user experience (such as slow state proof bridges) or implementation difficulties. On the other hand, in the dark forest world of blockchain, cross-chain bridges have always been fierce targets of hackers. Each time a cross-chain bridge encounters trouble, it brings huge losses:

• In July 2021, the cross-chain asset bridge project ChainSwap was attacked, resulting in a loss of nearly $8 million in assets;
• In January 2022, Qubit Finance's cross-chain bridge was attacked by hackers, resulting in a loss of over $80 million;
• In February 2022, Wormhole was attacked by hackers, resulting in a loss of over $320 million;
• In August 2022, the cross-chain bridge Nomad was stolen of over $190 million in encrypted assets.

The Bitcoin layer 1 asset issuance protocol RGB++ comes with the Leap function, which allows RGB++ assets to freely transfer between L1 (Bitcoin blockchain) and L2 (CKB blockchain or other UTXO stack-based chains). This type of bridgeless cross-chain transfer is permissionless, trustless, secure, and efficient, representing a new paradigm for cross-chain transactions.

This article will introduce the basic principles, advantages, tutorials, and precautions of Leap bridgeless cross-chain in simple and understandable language.

Leap: Bridgeless Cross-Chain

Before introducing the bridgeless Leap cross-chain, it is necessary to first introduce the minting principle and ownership transfer of RGB++ assets.

Issuing encrypted assets on the Bitcoin blockchain through the RGB++ protocol essentially involves associating Bitcoin UTXOs or writing a commitment on the Bitcoin chain. For example, if Alice issues 100 units of Test tokens on the Bitcoin blockchain using the RGB++ protocol, it will appear as a UTXO of 546 satoshis received in a Bitcoin address controlled by Alice, which is associated with 100 units of Test tokens. Simultaneously, a Cell (which is essentially a smarter UTXO) containing the explanation of the RGB++ asset (i.e., 100 units of Test tokens) and its unlocking condition is generated on the CKB blockchain. This Cell will only be spent when the 546 satoshis UTXO of Alice is spent.

When Alice transfers 60 units of Test tokens to Bob, it will appear as Alice spending the original UTXO associated with 100 units of Test tokens on the Bitcoin blockchain and receiving a new UTXO of 546 satoshis, which is still associated with 40 units of Test tokens. Meanwhile, Bob's address will receive a UTXO associated with 60 units of Test tokens. On the CKB blockchain, the original Cell will be spent, generating two new Cells: one containing the explanation of 40 units of Test tokens and the other containing the explanation of 60 units of Test tokens. Their spending conditions are that the corresponding Bitcoin UTXOs must be spent before they can be spent.

From the above example, it can be seen that the ownership of RGB++ assets is tied to Bitcoin UTXOs. Whoever can spend this UTXO can unlock the corresponding RGB++ assets because the spending condition of the Cell containing the explanation of the RGB++ assets is the transfer of the Bitcoin UTXO.

If we construct an RGB++ transaction on the Bitcoin blockchain and set its unlocking condition to be a UTXO on another chain instead of a Bitcoin UTXO, the asset will Leap to the other chain because the next spending of this asset will require unlocking by a UTXO on another chain. This is the basic principle of bridgeless Leap cross-chain, a completely decentralized process without the use of any cross-chain bridges or multi-signature addresses, and without any trust assumptions.

Of course, there are some details to be aware of when performing Leap operations, such as the need to confirm through multiple blocks to avoid block reorganization. For more knowledge about the RGB++ protocol and Leap, you are welcome to watch Cipher's public class "Overview of BTC Layer 1 Asset Protocol":

https://youtu.be/mgUxYU5tcJM?si=VWWraXbHu3DMAL64&t=3725

Advantages of Leap Bridgeless Cross-Chain

From the introduction of the basic principles above, it can be seen that Leap does not use any cross-chain bridges or multi-signature addresses. It is a truly permissionless, trustless, secure, and efficient cross-chain solution.

1. Permissionless

Suppose I deploy a new BRC20 token today and approach the project or operator of a multi-signature cross-chain bridge, hoping to cross to L2. It is highly likely to be rejected. Multi-signature cross-chain bridges often only support the pledging of a few top assets and the generation of corresponding wrapped assets, and do not support assets with low trading volume or insufficient popularity. This is because deploying contracts, setting up multi-signatures, monitoring changes in multi-signature addresses, and generating wrapped assets all require a significant amount of human and material resources.

In contrast, the Leap bridgeless cross-chain feature of the RGB++ protocol does not have this problem and is completely permissionless. If you issue a meme coin on the Bitcoin blockchain today through the RGB++ protocol, you can Leap to the CKB blockchain at any time and then Leap back freely.

2. Trustless

In traditional multi-signature cross-chain bridges, users pledge or lock encrypted assets into multi-signature addresses. Users need to trust that the operators of the cross-chain bridge will not act maliciously, embezzle funds, or run away because the assets are no longer under the user's control once they are locked in.

With the RGB++ protocol's Leap cross-chain, as it does not use any cross-chain bridges or multi-signature addresses, and there are no intermediaries, there is naturally no need for trust assumptions.

3. Security

Multi-signature cross-chain bridges have always been fierce targets of hackers because everyone's assets are locked in a multi-signature address. Once a successful attack occurs, a large amount of assets can be stolen, resulting in losses of several million, tens of millions, or even hundreds of millions of dollars each time a cross-chain bridge encounters trouble.

The RGB++ protocol's Leap bridgeless cross-chain transfers assets point-to-point, and the assets are always controlled by the user's private key, making it much more secure.

4. Efficiency

For Leap bridgeless cross-chain transfers using the RGB++ protocol, to avoid block reorganization, it is necessary to confirm through multiple blocks, usually taking a little over an hour (depending on the block generation speed and network congestion, especially on the Bitcoin network). For users, although this time is slightly slower than that of multi-signature cross-chain bridges, it is within an acceptable range, especially considering the security and trustless advantages of Leap cross-chain.

5. Other Advantages

The RGB++ protocol's Leap bridgeless cross-chain not only supports fungible tokens but also supports non-fungible tokens (referred to as DOBs, read more about Spore DOBs here).

Tutorial for Leap Bridgeless Cross-Chain

Currently, the JoyID wallet fully supports the bridgeless Leap cross-chain of RGB++ assets (Coins and DOBs) between L1 and L2. Below is a tutorial for performing bridgeless Leap cross-chain using the JoyID wallet:

1. From L1 to L2 (BTC → CKB)

After logging into the JoyID wallet, switch to the Bitcoin network, click the "Leap" button, select the Coins or DOBs you want to Leap, choose "Bitcoin L2 (CKB)" in the sending interface, enter the CKB address and quantity, select the miner fee, and finally click "Send" and confirm the signature.

2. From L2 to L1 (CKB → BTC)

The Leap from L2 to L1 consists of two stages: the Preparing stage and the Complete stage, each requiring the signing of a BTC transaction and a CKB transaction.

Preparing stage:

1. Log in to the JoyID wallet and switch to the Nervos CKB network.
2. Click the "Leap" button.
3. Enter the Bitcoin address.
4. Select the RGB++ assets you want to Leap back to L1 and enter the quantity.
5. Choose the FeeRate (ensure that your Bitcoin wallet has enough UTXO balance to pay the fee).
6. Click the "Leap To Bitcoin L1" button.
7. Click the "Prepare" button.
8. Sign to confirm the transaction.
9. You can track the transaction status by clicking "Track Status" or in the "Ongoing Leaps" page.

Complete stage:

1. Wait for the Bitcoin mainnet to confirm the transaction, then click "Complete".
2. Verify the leap information, click "Complete" again, and wait for the CKB mainnet confirmation. You can track the status in Settings-Activity-Leap.
3. After the CKB mainnet confirmation, switch to your Bitcoin wallet to view your RGB++ assets.

Precautions

Assets issued through the RGB++ protocol are "parasitic" or "bound" to Bitcoin UTXOs, specifically bound to a UTXO of 546 satoshis. If this UTXO is spent, the corresponding RGB++ assets will also be spent.

How to avoid accidentally spending the UTXO bound with RGB++ assets? The JoyID wallet sets a threshold, which is currently 1200 satoshis. UTXOs below this threshold will not be spent as miner fees or regular BTC transfers. Different wallets may have different thresholds, so to avoid accidental spending, it is recommended to use the JoyID wallet to store and transact with RGB++ assets.

Furthermore, it is currently not recommended to use tools developed by community members to Leap assets from the CKB chain to the Bitcoin chain. This is because some tools do not follow the RGB++ standard when binding Bitcoin UTXOs—binding to UTXOs exceeding 1200 satoshis. When users use the JoyID wallet to send BTC transactions, the wallet may easily spend these UTXOs as miner fees or regular UTXOs. Therefore, it is best to use the JoyID wallet when performing Leap operations.

免责声明：本文章仅代表作者个人观点，不代表本平台的立场和观点。本文章仅供信息分享，不构成对任何人的任何投资建议。用户与作者之间的任何争议，与本平台无关。如网页中刊载的文章或图片涉及侵权，请提供相关的权利证明和身份证明发送邮件到support@aicoin.com，本平台相关工作人员将会进行核查。