Protecting a private blockchain using a public blockchain can be achieved through several techniques that leverage the security, immutability, and decentralization of public networks while maintaining the confidentiality and efficiency of private networks. Here’s how:
🔹 How it works:
Instead of storing private data directly on the public blockchain, you hash the private blockchain’s critical data (blocks, transactions, or state) and record the hash on a public blockchain like Bitcoin or Ethereum. This ensures that if anyone tries to tamper with the private blockchain, the hashes won’t match, proving the integrity of the private chain.
🔹 Example:
A supply chain company runs a private blockchain but stores cryptographic hashes of transactions on Ethereum to prove their authenticity without exposing private data.
🔹 Projects/Protocols:
OpenTimestamps (Bitcoin-based proof of existence). Chainlink’s DECO (privacy-preserving oracle for verification).
🔹 How it works:
A private blockchain can interact with a public blockchain via smart contracts, where only specific verified data is shared. Allows private chains to benefit from public security while keeping sensitive data hidden.
🔹 Example:
A private medical records blockchain validates patient identities via a public blockchain without exposing personal data.
🔹 Projects/Protocols:
Hyperledger Fabric + Ethereum Polkadot’s parachains Cosmos (IBC - Inter-Blockchain Communication protocol)
🔹 How it works:
Instead of revealing private blockchain transactions, a Zero-Knowledge Proof (ZKP) allows verification of data validity without disclosing actual data. Public blockchains can verify private blockchain transactions without exposing details.
🔹 Example:
A private DeFi lending protocol could prove it holds enough collateral on a public blockchain without revealing user details.
🔹 Projects/Protocols:
ZK-SNARKs & ZK-STARKs (used in zkSync, StarkNet, and Aztec Network).
🔹 How it works:
Smart contracts on a public blockchain act as a decentralized notary, certifying transactions or agreements from a private blockchain. Reduces fraud risks by ensuring an immutable proof of existence.
🔹 Example:
A legal firm using a private blockchain for contracts can notarize key details on Ethereum for dispute resolution.
🔹 Projects/Protocols:
Civic (decentralized identity verification). NotaryChain (blockchain-based notarization).
🔹 How it works:
Private blockchains can store encrypted backups or checkpoints on a public blockchain. If a private blockchain is compromised, it can be restored using public blockchain proofs.
🔹 Example:
A private corporate blockchain backs up state changes onto Ethereum every 100 blocks to ensure disaster recovery.
🔹 Projects/Protocols:
Filecoin, Arweave, IPFS (decentralized storage for immutable backups).