As the online world becomes more privacy-oriented, Zero Knowledge Proof (ZKP) is emerging for their ability to prove that something is true without revealing the underlying data behind it. But did you know that there are two main types of ZKP?
They are:
Interactive Zero Knowledge Proof
Non-Interactive Zero Knowledge Proof (NIZKs)
In this blog, we’ll explore what each of these means, how they work, and where they’re used — in simple, beginner-friendly terms.
What Is a Zero Knowledge Proof Again?
Just a quick refresher: A Zero Knowledge Proof lets a person (called the prover) convince someone else (the verifier) that they know a secret or that something is true — without ever revealing what that secret is.
It's like revealing you're aware of the answer to a riddle without actually speaking out the answer.
Interactive Zero Knowledge Proof
How It Works:
In an interactive ZKP, the verifier and prover must converse back and forth several times. The verifier asks challenges, and the prover responds so they can demonstrate they know the secret.
Envision a live interview or conversation.
Example (Real-World Analogy):
For instance, imagine you want to prove you have the password to the door of a cave without actually giving the password. You enter the cave, follow one of two paths, and your friend (the verifier) asks you to leave using a specific path. When you can always get away with it — in most runs — they conclude you know the password even though you never provide it.
✅ Benefits:
Very secure when properly implemented
Best suited for environments where communication is feasible back-and-forth
❌ Limitations:
Requires ongoing interaction between verifier and prover
Not ideal for use cases like blockchain, where communication is limited
Non-Interactive Zero Knowledge Proof (NIZK)
How It Works:
In a non-interactive ZKP, no exchange takes place. The prover makes one-off proof using some copyright magic (usually some shared public value), and the verifier can check at any time — without needing to communicate with the prover.
It's akin to handing someone an envelope that's already sealed containing all the proof. They can open it up and verify everything for themselves.
Real-World Use Case:
This is the kind of ZKP deployed in blockchains, smart contracts, and copyright — where you don't even know who the verifier is or when they're going to verify.
✅ Benefits:
Faster and more scalable
Ideal for blockchain and decentralized settings
Provable versions can be shared publicly and anyone can validate them
Drawbacks:
Slightly more complex to set up
Prone to depending on a "trusted setup" or specific assumptions (although newer methods such as zk-STARKs do not)
Final Thoughts
It is crucial to grasp the difference between interactive and non-interactive Zero Knowledge Proof because ZKP will become more ubiquitous in digital privacy, security, and Web3 application.
Interactive proofs are like a live conversation, while non-interactive proofs are like writing a note which anyone can verify.
As technology evolves, expect non-interactive ZKP to take an unprecedented role in fueling the next wave of decentralized, secure systems — all without sharing your data.