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# What is post-quantum cryptography?

Abdul Mateen

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Post-quantum cryptography commonly directs to public-key cryptography strategies created to be invulnerable to quantum computer-based invasions.

Post-quantum cryptography (occasionally called quantum-proof, quantum-safe, or quantum-resistant) directs to cryptographic algorithms (usually public-key algorithms) that are protected against an invasion by a quantum computer. Post-quantum cryptography equips us for the era of quantum computing by revising existing mathematical-based algorithms and standards.

The evolution of cryptographic approaches can be implemented using today’s classical computers but will be impervious to attacks from tomorrow’s quantum ones.

## Why do we need post-quantum cryptography?

Public and private keys are mathematically connected. Today’s techniques for public-key cryptography depend on mathematical issues that traditional computers find quite difficult, such as calculating the prime factors of a very large number.

Quantum computers process information in a way that allows them to do some types of calculations that classical computers can’t.

The need for post-quantum cryptography is based on four major factors.

1. Public-key cryptography is commonly used in online communication where Bob wants to send a message to Alice. To do this privately, Alice generates a public and private key pair. Bob uses the public key to encrypt a message that Alice’s private key can only decrypt.

2. Classical computers find recognizing a private key quite difficult because only Alice has the private key, but her public key is available to everyone. And classical computers cannot find the current mathematical problems of the link between private and public keys.

3. Quantum computers can estimate a private key very quickly because quantum computers process information differently from conventional computers, permitting new types of calculation. That encloses an algorithm that can easily figure out a private key purely from the public key.

4. Quantum hackers could sabotage trust and privacy online because, without new public-key cryptography benchmarks, quantum computer-equipped hackers could listen in on lots of online communication and interfere with a system that relies on trust.

## Types of post-quantum cryptography

There are four basic types of post-quantum cryptography.

Types of PQC

### Code-based cryptography

Code-based cryptography is an approaching opponent for diversifying today’s public-key cryptosystems, which depend on the complexness of factorization or discrete logarithm issues.

Unlike public-key algorithms, Code-based cryptography is based on the issue of solving unknown error-correcting codes, assumed to be NP-hard. There are two simple code-based cryptography techniques named after Robert McEliece and Harald Niederreiter.

### Hash-based cryptography

A hash-based cryptography scheme is derived from a one-time signature (OTS), i.e., a signature scheme that must only use each key pair to sign a message. If an OTS key pair signs two different notes, this cab threatens the network, and a hacker will effortlessly forge fake signatures that expose the customer’s personal details.

### Multivariate cryptography

The foundation of multivariate cryptography schemes is based upon the challenge of solving non-linear equation structures over finite fields.

The primary layout is used for all Multivariate Public-Key Cryptosystems (MPKC), as they all rely on multivariate polynomials over a limited field.

In most possibilities, the polynomial equations are of degree two, resulting in multivariate quadratic polynomials, which are yet credited with being solved as NP-hard.

### Lattice-based cryptography

Lattice-based cryptographic algorithms are mainly established on the problem with the nearest vector or the shortest vector problem.

In most lattice-based cryptographic algorithms, the cryptographic builders are very time-efficient and straightforward while still delivering security guarantees founded on the worst-case hardness.

This method uses both lattices and a generalization of the issue of parity learning. Given an $n$-dimensional vector space, a lattice is a precise interpretation of points with a periodic structure used in various fields.

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Abdul Mateen