Nov 29, 2020

**Introduction to Zero-Knowledge Proof (ZKP)**

Almost every individual with a smartphone uses apps that collect and, most probably, resell their personal data. On the other hand, people who don’t use apps also have their phone operating system or their network provider collecting their data. So, how can people get complete control over their data?

In recent times, blockchain and cryptography have definitely garnered a lot of attention for safeguarding user data. Zero-Knowledge Proof is one of the cryptographic mechanisms that establish the foundation of cryptographic protocols. Let us explore more information about the Zero-Knowledge Protocol, its features, benefits, and applications.

Basically, the Zero Knowledge Proof involves a person providing proof to another person about having some sort of information without revealing the information. The person providing the proof is known as the prover, and the other person is known as the verifier. Therefore, the zero-knowledge protocol helps in communicating the proof of possessing specific information without actually revealing the information.

The applications of zero-knowledge proof in blockchain transactions primarily refer to the identification functionalities. Just by providing the final output, the prover can show to the verifier that they can complete a process or compute something without actually revealing the computational process or the input. On the other hand, the verifier is capable of learning only about the output.

**Distinguishing Zero-Knowledge Proofs**

So, how is it possible to differentiate a ZKP from other cryptographic protocols? The answer to this question is evident in the three distinct criteria for characterizing a zero-knowledge protocol mentioned as follows,

**Completeness:**The zero-knowledge proof should convince the verifier about the fact that the prover actually knows what they claim to know.**Soundness:**In event of false information, the protocol cannot convince the verifier that the information provided by prover is true.**Zero-knowledge:**Even if the statement is true or false, the verifier cannot know anything other than that.

**Proof of Identity**

Zero-knowledge protocols are primarily used for identification schemes. The conventional secret-key and public-key schemes presented many setbacks. For example, the secret key, pin, or password of identification schemes can be easily discovered through exhaustive search. In addition, biometric parameters such as retinal scans, facial recognition, and fingerprints are also subject to various disadvantages. Zero-knowledge proofs can completely change the equation by retaining integrity of information and its control with the prover.

**Types of Zero-Knowledge Proofs**

The next important aspect for understanding zero-knowledge proofs refers to the variants. You can find two types of zero-knowledge proofs, such as interactive and non-interactive variants.

The interactive ZKPs generally involve performing a series of actions for convincing the verifier about a specific fact. The only setback with interactive variant of ZKPs is limited transferability and requirement for proving facts to the verifier multiple times.

The non-interactive ZKPs, on the other hand, involve delivery of proof that anyone could verify on their own. In this case, the verifier has to set a random challenge that the prover has to solve. Furthermore, an interactive **ZKP** could convert to a non-interactive variant by using a hash function for selecting the challenge. It would not involve any form of interaction with the verifier. Non-interactive ZKPs don’t require repeated transactions between the verifier and prover. The proof in non-interactive ZKPs is present in a single message, provided to verifier from the prover.

**ZK-SNARK**

Zero-Knowledge Snark or Succinct Non-Interactive Arguments of Knowledge (ZK-SNARKs) are basically a particular variant of non-interactive zero-knowledge protocol. They are ‘zero-knowledge’ as they don’t reveal any information to verifier. ZK-SNARKs are ‘succinct’ because of a quick verification of the proof. They are ‘non-interactive’ because of the limited requirement of repeated interaction between prover and verifier. The ‘arguments of knowledge’ aspect of ZK-SNARKs points out to the presentation of soundproof.

**Applications of Zero-Knowledge Proofs**

An illustration of the applications of Zero-Knowledge Proofs can help in understanding its potential effects. Here are some of the notable applications of ZKPs.

**Authentication Systems**

Zero-knowledge proofs can turn a new page in moving towards passwordless logins by depending on zero-knowledge password proof.

**Private Purchases**

Smart cards leveraging zero-knowledge proof can be ideal for identifying cardholders to merchants without disclosing knowledge to merchants.

**Private Blockchains**

ZKPs can help in verifying the validity of transactions even with undisclosed information about sender, recipient, and transaction details. The best example of the application of zero-knowledge proof in blockchain is Zcash, which utilizes ZK-SNARKs.

**Secure Bitcoin Transactions**

Bitcoin allows sending money by producing a preimage of a SHA256 hash. In this case, the condition exists that if the receiver fails to produce the preimage, the money will return back. ZKPs can help in enforcing the preimage of the hash as a key for unlocking certain data. As a result, ZKPs can provide exceptional functionality for development of exotic protocols or conducting sensitive transactions.

**Conclusion**

As you can notice clearly, zero-knowledge proofs have massive potential for safeguarding information integrity. They can allow others for verification of specific attributes of data without revealing the information. As a result, it can impose considerable changes in the domain of healthcare, finance, and other sectors. So, you can definitely expect a new era of flexibility for transactions with proven safeguards for data privacy.