Zero-Knowledge Proof: Proving Without Revealing the Data

Imagine you're hanging out at a café. You place your wallet on the table.

A friend comes by and asks:

"Hey, can I borrow some money?"

If you trust them, you'd simply: Grab your wallet,

Take some cash,

Hand it to them.

Done.

Now imagine if instead, they grabbed your wallet and started looking through everything inside:

How much money you have

Your debit and credit cards

Your ID, maybe even your driver’s license

All your personal information is exposed without your control.

But they only needed one thing:

Confirmation that you can give them some money.

Revealing everything inside your wallet is unnecessary and irrelevant.

Even worse, the more information you expose, the higher the risk it could be misused.

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What is Zero-Knowledge Proof (ZKP)?

Zero-Knowledge Proof (ZKP) allows one party (the prover) to prove to another party (the verifier) that a certain statement is true—without revealing the underlying secret or data that proves it.

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Application in Blockchain

In blockchain, ZKPs allow transactions to be verified without revealing their details, enhancing both privacy and scalability of the network through methods like zk-rollups.

This process speeds up transactions and reduces network congestion without sacrificing security.

In short, ZKP is a cryptographic protocol that lets you prove a claim without revealing the data behind it—using secure and efficient mathematical interactions.

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Core Principles of ZKP:

1. Completeness:

If the statement is true and the prover follows the protocol, the verifier will be convinced of its validity.

2. Soundness:

If the statement is false, a dishonest prover cannot convince the verifier.

3. Zero-Knowledge:

The verifier gains no additional information beyond the fact that the statement is true.

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Two Types of ZKP:

1. Interactive ZKP

Involves back-and-forth communication between the prover and the verifier.

Less efficient for blockchain due to the need for continuous interaction.

2. Non-Interactive ZKP (NIZK)

Uses special algorithms and randomness (like hash functions).

Requires only a single proof submission that can be verified directly.

More suitable for blockchain systems.

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How ZKP Works (Interaction Model):

The verifier sends a challenge.

The prover responds with an answer that mathematically proves they know the secret,

without revealing what the secret actually is.

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Use Cases in Blockchain:

1. Private Transactions

ZKPs let users prove that a transaction is valid without disclosing its details.

Examples:

Zcash uses zk-SNARKs to hide the sender, receiver, and transaction amount.

Aztec Protocol (on Ethereum) enables private yet verifiable transactions using ZKPs.

2. Scalability via Rollups

ZKPs reduce the load on the mainnet by doing computations off-chain

and submitting only a proof to the mainnet.

Examples:

zk-Rollups (e.g., StarkNet, zkSync) process thousands of transactions off-chain

and submit a single ZK proof on-chain to validate the batch.

3. Verifiable Computation

ZKPs allow users to prove a computation was done correctly without revealing the input.

Example:

Used in decentralized voting systems, so voters can verify their vote was counted

without revealing who they voted for.