What is zero-knowledge encryption?

Zero-knowledge cryptography (also known as zero-knowledge protocols) is a cryptographic concept in which one party (the prover or sender) proves to another party (the verifier or receiver) that a piece of information is true without revealing the information itself. This means that after the exchange of information, the verifier learns none of the details of the information, but can still be sure that the prover actually knows or is in possession of the information.

The term zero knowledge refers to the fact that the verifier does not receive any additional information about the secret information throughout the entire process. Only the truth of the statement is confirmed without the information itself being disclosed.

The basic principle of zero-knowledge protocols:

Zero-knowledge encryption works on the basis of mathematically secure protocols that enable the prover to provide a truthful result without the verifier ever receiving the actual information. In other words,

• the prover proves that they know or possess something without directly revealing the information.
• The verifier can be sure after the verification that the prover actually knows what he claims, but he learns nothing further about the information.

A frequently cited example of zero-knowledge is the classic ‘mountain problem’, which vividly explains the basic idea.

Example: Zero-knowledge protocol with the mountain problem

Let’s imagine there is a secret cave in the shape of a ring with two entrances – one on the left and one on the right. The prover (A) wants to prove to the verifier (B) that they know the secret key that allows them to pass through the ring from one entrance to the other. The verifier only sees that A enters the cave, but not which entrance they go through.

1. Step 1: A enters the cave and randomly selects an entrance (left or right).
2. Step 2: B asks A to return through a specific entrance – either left or right.
3. Step 3: A must prove that he knows the key by returning through the correct entrance requested by B.
4. Step 4: If A does this correctly several times, without being able to go through the same entrance in each case, B becomes increasingly certain that A really knows the key.

In this case, however, B never learns the actual key, but can only determine that A is actually able to enter the ring and pass through both entrances, which proves that he knows the key.

Applications of zero-knowledge encryption:

Zero-knowledge protocols are used in various areas of cryptography and data security, especially in scenarios where privacy protection is crucial.

1. Passwordless authentication: A zero-knowledge protocol can be used to authenticate users without the user revealing their password. Instead, a kind of ‘proof’ is provided that the user knows the correct password without it ever being transmitted.

• Example: Login processes where a server verifies that the user knows the correct credentials, but the password is never sent over the network.

1. Privacy in transactions: In cryptocurrencies like Zcash, zero-knowledge cryptography is used to verify transactions without revealing details such as the amount or parties involved. This ensures user privacy and anonymity.
2. Hidden data verification: In systems that store sensitive data (e.g. health data, financial data), zero-knowledge protocols can be used to check whether a person meets certain criteria (e.g. is of a certain age) without the person revealing their exact age or other private data.
3. Trusted calculations: Zero-knowledge protocols make it possible to verify calculations or statements without disclosing the underlying data. This is particularly useful in cloud computing environments where users want to perform calculations without disclosing their data to the cloud provider.

Advantages of zero-knowledge encryption:

1. Privacy and security: Zero-knowledge protocols guarantee that no sensitive information is transmitted, which increases privacy and data security.
2. Trusted verification: They allow a party to verify their claim without the verifier receiving any of the underlying information.
3. Preventing data misuse: Since the information is not disclosed, there are fewer risks of data misuse and hacking.

Disadvantages and challenges:

1. Complexity and computational overhead: Zero-knowledge protocols can be computationally intensive and complex to implement, which increases the resource overhead for protocol verification and execution.
2. Limitations on use: In certain scenarios, zero-knowledge protocols may be less practical if very fast or scalable solutions are required.
3. Increased infrastructure requirements: Implementation often requires a robust and secure infrastructure to ensure the integrity of the protocols.

Conclusion:

zero-knowledge cryptography is a powerful concept based on the idea that you can prove something without directly disclosing it. In an increasingly privacy-conscious world, zero-knowledge protocols offer important ways to preserve privacy and increase security while still enabling trust and verification. This technology plays a particularly crucial role in sensitive areas such as financial services, cryptocurrencies and authenticated access systems.