Post-Quanten-Kryptografie Image © DALL-EPost-Quanten-Kryptografie (Image © DALL-E)

Why do we need post-quantum cryptography?

Encryption has been around since ancient times, because the interest in transmitting important or secret messages securely from A to B has existed for a long time. In cryptography modules at colleges and universities, the simplest of them, such as the Caesar cipher, were tested right from the start. Nowadays, encryption plays an even more important role, as all communication should ideally be encrypted. Even though there are no real quantum computers available to buy yet and the technology is still under development, researchers are trying to think ahead. Current encryption methods on the internet are basically based on two different building blocks that are considered “too hard to compute”. Of course, this is very simplistic for the sake of illustration.

For cryptographic systems, the factorization assumption plays an important role and, secondly, the discrete logarithm assumption. Both are used in cryptographic systems, especially on the Internet. However, the trend here is to rely increasingly on the discrete logarithm. The security of cryptographic systems basically lies in the fact that there is no efficient way for attackers or unauthorized persons to break the encryption quickly. However, this is based on current computing power and capacity.

And this is where quantum computers come into play. If quantum computers can factorize cryptographic systems efficiently or perform the discrete logarithm, all communication worldwide would be at risk and this worries researchers - and rightly so!

What is post-quantum cryptography?

The assumption that quantum computers could possibly carry out the calculation more efficiently and that the previous encryption could then no longer be considered secure gave rise to the need for new methods and algorithms that are also secure against quantum computers. But this is by no means easy! In response, the National Institute of Standards and Technology (NIST) has launched a worldwide

The National Institute of Standards and Technology (NIST) of the United States has initiated a process to evaluate and standardize post-quantum cryptography algorithms. In July 2022, NIST announced the first four algorithms selected as part of its Post-Quantum Cryptography Standardization Project. This process is intended to help develop a set of standards for post-quantum cryptography that can be widely implemented to keep future communications and data secure.

Post-Quantum Cryptography (PQC) Challenge Winners

The National Institute of Standards and Technology (NIST) Post-Quantum Cryptography (PQC) Challenge selected several techniques as finalists to develop standards for the era of quantum computing. These techniques fall into several categories of cryptography, including public-key encryption and digital signatures, which aim to be resistant to attacks by quantum computers. The selection of finalists was announced in July 2022 and includes the following algorithms

Digital signature methods

  • CRYSTALS-DILITHIUM: Developed for digital signatures with a focus on security against quantum computer attacks.
  • FALCON: Focus on small signature sizes, based on the difficulty of finding short vectors in lattices.
  • SPHINCS+: A hash-based signature algorithm that serves as an alternative to structure-based approaches such as lattices and code-based schemes.

Method for public key encryption and key exchange:

  • CRYSTALS-KYBER (public-key encryption): A lattice-based key exchange and encryption algorithm known for its security and efficiency.
  • NTRU (Public-Key Encryption):** One of the oldest lattice-based cryptographic algorithms, known for its efficiency and security.
  • SIKE (Supersingular Isogeny Key Encapsulation): Based on the mathematical structure of elliptic curves and aims to provide an alternative to traditional factorization and discrete logarithm-based schemes.

The NIST has announced that these algorithms will be part of the first standard for post-quantum cryptography to ensure digital security in the era of quantum computing.

This selection represents a significant step in the development of future security standards aimed at protecting digital systems and data even after the advent of viable quantum computers.