KoinlyticsWhen most people say 'blockchain', they mean a public one. Bitcoin, Ethereum, Solana. Anyone can join, anyone can read, no company controls it. But a whole other category exists: private (or 'permissioned') blockchains, which look completely different in every way that matters.
Public chains
The blockchains you know:
- Anyone can run a node
- Anyone can read all data
- Anyone can send a transaction
- Nobody can freeze or reverse anything
- Slower and more expensive than a traditional database
The design goal is censorship resistance. That is why Bitcoin can survive being banned in individual countries and Ethereum can host protocols that no company owns.
Private / permissioned chains
The blockchains banks and enterprises build:
- Only whitelisted parties can run a node
- Data is visible only to permissioned readers
- Only permissioned parties can transact
- Governance can pause, freeze, or revert
- Fast and cheap because you know all the participants
Examples: JPMorgan's Kinexys (dollar payments between banks), R3 Corda (banking consortiums), Hyperledger Fabric (Walmart supply chain tracking).
Why both exist
Public chains solve one problem: how do we agree on facts without a central party? Private chains solve a different problem: how do we get some of the benefits of a shared ledger (audit trail, real-time settlement) while keeping the transaction data private and the governance under our control?
A bank cannot use a public chain for internal settlement (the transaction data would be public). But it can use a private chain to move dollars between departments faster than SWIFT allows.
Side by side
Which one is 'better'?
Wrong question. They are different tools. A bank moving dollars between branches does not need Bitcoin-level censorship resistance. A Venezuelan citizen sending money to family abroad absolutely does. Pick the tool that matches the threat model.
Where this gets interesting
Increasingly, public-chain tokens (like USDC) are being adopted by regulated institutions who normally would prefer private chains. And private-chain networks are experimenting with 'bridges' to public chains so users can move value between them. The line between the two is blurring, but for now, they remain two different products with two different customer sets.