Bitcoin Layer 2's NFT bridge
Cross-chain NFT Bridge enables secure NFT transfers between different Bitcoin Layer 2 networks through a dual-verification process:
Sending NFTs Across Chains:
Source Chain Actions
Original NFT on source chain (e.g., Citrea) initiates transfer
When starting an NFT bridge transfer, you select the NFT you want to move from Citrea (source chain) and initiate the transfer process, which locks your NFT in a secure contract and generates a unique transfer ID to track its movement.
Asset gets burned, generating proof of burn
When bridging your NFT, the system permanently locks (burns) your original NFT on Citrea and creates a unique proof of this burn, which acts like a digital receipt proving you owned and locked the original NFT.
Oracle Service monitors and validates burn event
Oracle services automatically watch for and verify that your NFT was properly burned on Citrea, acting like digital security guards that confirm and record the permanent lock of your NFT before allowing the bridge process to continue.
Creates Merkle proofs and validates chain state
Special verification tools create a Merkle proof (like a tamper-proof digital fingerprint) and check the entire network's current state to ensure your NFT burn was properly recorded and verified before proceeding with the bridge.
Signs proof for verification
The system creates a secure digital signature for all the collected proofs (burn proof, Merkle proof, and state validation), which serves as the final verification stamp needed to mint your NFT on the destination chain.
Bridge Transfer Process
Relayer Service prepares delivery protocol
The relayer service packages all verified proofs and NFT data into a secure message, preparing it for safe delivery to the destination network (like preparing a secured digital package with all necessary documents for cross-chain transfer).
Handles gas fee initialization for destination chain
The system calculates and prepares the required gas fees (transaction costs) on the destination chain, ensuring enough funds are ready to create your NFT on the new network, like having the right postage ready before sending a package.
Emits smart contract function for transfer
The system sends out a specialized command (smart contract function) that triggers the NFT creation process on the destination network, like sending an automated instruction to mint your new NFT based on all the verified proofs.
Moves verified data to destination chain
The bridge protocol securely sends all your verified NFT data (including ownership proof, metadata, and burn verification) to the destination chain, ensuring everything needed to recreate your NFT is properly transferred.
Receiving Chain Actions
Destination chain (e.g., BOB) receives transfer request
The destination network (in this case, BOB) receives the complete package of verified data and transfer request, preparing to create your new NFT based on all the security proofs and information sent from Citrea.
Verifies oracle proofs for security
The destination chain carefully checks all the security proofs provided by the oracle services, confirming that your NFT was properly burned on Citrea and all verification steps were completed successfully.
Mints new wrapped asset after verification
The destination chain creates (mints) your new wrapped NFT after all security checks pass, making an exact copy of your original NFT that's now ready to use on the new network while maintaining its connection to the burned original on Citrea.
Asset becomes available for trading
Once all verifications are complete, your newly minted NFT becomes active and unlocked on the destination chain, allowing you to freely trade, transfer, or use it just like any other NFT on that network.
Security Features:
Multi-layer verification
Multi-layer verification uses multiple independent security checks (ownership verification, burn proof, oracle validation, state checks, and cryptographic proofs) to ensure your NFT transfer between chains is completely secure and authentic.
Oracle-based monitoring
Oracle-based monitoring consists of multiple independent nodes that continuously watch, verify, and validate the NFT bridge process, acting like digital security cameras that ensure every step of your NFT transfer is properly executed and recorded.
Automated proof generation
Automated proof generation creates secure digital certificates (like burn proofs, Merkle proofs, and state validations) without human intervention, ensuring consistent and tamper-proof verification of your NFT's movement between chains.
Smart contract security
Smart contract security ensures your NFT bridge transfer follows predefined, immutable rules coded into the blockchain, automatically enforcing security checks and validation steps while preventing unauthorized access or modifications to the process.
State validation checks
State validation checks verify the current condition of both blockchain networks (source and destination) to ensure your NFT's information and ownership status are accurately recorded and synchronized during the bridge transfer process.
This ensures your NFTs move safely between Layer 2 networks while maintaining connection to Bitcoin's security. Each transfer is verified, validated, and secured through multiple checkpoints.
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