Image: Adobe Stock
Most currently used public-key cryptosystems like e.g. the Rivest, Shamir and Adleman (RSA) cryptosystem and Elliptic Curve Cryptosystems (ECC) are under the threat of attacks performed on quantum computers using e.g. Grover’s and/or Shor’s algorithm. While symmetric cryptosystems can defeat quantum attacks with increased key sizes, asymmetric cryptosystems, including the examples mentioned above, are entirely broken once quantum computers of sufficiently large size are available.
In order to ensure secure communication in the age of powerful quantum computers, quantum-resistant (or post-quantum) cryptosystems are required. Compared to the currently know cryptosystems, most quantum-resistant cryptosystems suffer from large key sizes.
The main challenge in designing competitive quantum-resistant cryptosystems constitutes in reducing the key size while keeping the security level high. The group "quantum-resistant cryptography (QRC)" considers the analysis and development of cryptographic schemes that enable secure communication in the age of powerful quantum computers. This includes the development and improvement of code-based cryptosystems, efficient en- and decryption algorithms and new methods for the cryptanalysis.
Quantum computer in the laboratory (Image: Adobe Stock)